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Diffstat (limited to 'module/zfs/arc.c')
| -rw-r--r-- | module/zfs/arc.c | 10565 |
1 files changed, 10565 insertions, 0 deletions
diff --git a/module/zfs/arc.c b/module/zfs/arc.c new file mode 100644 index 000000000000..bd1a993dca92 --- /dev/null +++ b/module/zfs/arc.c @@ -0,0 +1,10565 @@ +/* + * CDDL HEADER START + * + * The contents of this file are subject to the terms of the + * Common Development and Distribution License (the "License"). + * You may not use this file except in compliance with the License. + * + * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE + * or http://www.opensolaris.org/os/licensing. + * See the License for the specific language governing permissions + * and limitations under the License. + * + * When distributing Covered Code, include this CDDL HEADER in each + * file and include the License file at usr/src/OPENSOLARIS.LICENSE. + * If applicable, add the following below this CDDL HEADER, with the + * fields enclosed by brackets "[]" replaced with your own identifying + * information: Portions Copyright [yyyy] [name of copyright owner] + * + * CDDL HEADER END + */ +/* + * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2018, Joyent, Inc. + * Copyright (c) 2011, 2019, Delphix. All rights reserved. + * Copyright (c) 2014, Saso Kiselkov. All rights reserved. + * Copyright (c) 2017, Nexenta Systems, Inc. All rights reserved. + * Copyright (c) 2019, loli10K <ezomori.nozomu@gmail.com>. All rights reserved. + * Copyright (c) 2020, George Amanakis. All rights reserved. + * Copyright (c) 2019, Klara Inc. + * Copyright (c) 2019, Allan Jude + * Copyright (c) 2020, The FreeBSD Foundation [1] + * + * [1] Portions of this software were developed by Allan Jude + * under sponsorship from the FreeBSD Foundation. + */ + +/* + * DVA-based Adjustable Replacement Cache + * + * While much of the theory of operation used here is + * based on the self-tuning, low overhead replacement cache + * presented by Megiddo and Modha at FAST 2003, there are some + * significant differences: + * + * 1. The Megiddo and Modha model assumes any page is evictable. + * Pages in its cache cannot be "locked" into memory. This makes + * the eviction algorithm simple: evict the last page in the list. + * This also make the performance characteristics easy to reason + * about. Our cache is not so simple. At any given moment, some + * subset of the blocks in the cache are un-evictable because we + * have handed out a reference to them. Blocks are only evictable + * when there are no external references active. This makes + * eviction far more problematic: we choose to evict the evictable + * blocks that are the "lowest" in the list. + * + * There are times when it is not possible to evict the requested + * space. In these circumstances we are unable to adjust the cache + * size. To prevent the cache growing unbounded at these times we + * implement a "cache throttle" that slows the flow of new data + * into the cache until we can make space available. + * + * 2. The Megiddo and Modha model assumes a fixed cache size. + * Pages are evicted when the cache is full and there is a cache + * miss. Our model has a variable sized cache. It grows with + * high use, but also tries to react to memory pressure from the + * operating system: decreasing its size when system memory is + * tight. + * + * 3. The Megiddo and Modha model assumes a fixed page size. All + * elements of the cache are therefore exactly the same size. So + * when adjusting the cache size following a cache miss, its simply + * a matter of choosing a single page to evict. In our model, we + * have variable sized cache blocks (ranging from 512 bytes to + * 128K bytes). We therefore choose a set of blocks to evict to make + * space for a cache miss that approximates as closely as possible + * the space used by the new block. + * + * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" + * by N. Megiddo & D. Modha, FAST 2003 + */ + +/* + * The locking model: + * + * A new reference to a cache buffer can be obtained in two + * ways: 1) via a hash table lookup using the DVA as a key, + * or 2) via one of the ARC lists. The arc_read() interface + * uses method 1, while the internal ARC algorithms for + * adjusting the cache use method 2. We therefore provide two + * types of locks: 1) the hash table lock array, and 2) the + * ARC list locks. + * + * Buffers do not have their own mutexes, rather they rely on the + * hash table mutexes for the bulk of their protection (i.e. most + * fields in the arc_buf_hdr_t are protected by these mutexes). + * + * buf_hash_find() returns the appropriate mutex (held) when it + * locates the requested buffer in the hash table. It returns + * NULL for the mutex if the buffer was not in the table. + * + * buf_hash_remove() expects the appropriate hash mutex to be + * already held before it is invoked. + * + * Each ARC state also has a mutex which is used to protect the + * buffer list associated with the state. When attempting to + * obtain a hash table lock while holding an ARC list lock you + * must use: mutex_tryenter() to avoid deadlock. Also note that + * the active state mutex must be held before the ghost state mutex. + * + * It as also possible to register a callback which is run when the + * arc_meta_limit is reached and no buffers can be safely evicted. In + * this case the arc user should drop a reference on some arc buffers so + * they can be reclaimed and the arc_meta_limit honored. For example, + * when using the ZPL each dentry holds a references on a znode. These + * dentries must be pruned before the arc buffer holding the znode can + * be safely evicted. + * + * Note that the majority of the performance stats are manipulated + * with atomic operations. + * + * The L2ARC uses the l2ad_mtx on each vdev for the following: + * + * - L2ARC buflist creation + * - L2ARC buflist eviction + * - L2ARC write completion, which walks L2ARC buflists + * - ARC header destruction, as it removes from L2ARC buflists + * - ARC header release, as it removes from L2ARC buflists + */ + +/* + * ARC operation: + * + * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure. + * This structure can point either to a block that is still in the cache or to + * one that is only accessible in an L2 ARC device, or it can provide + * information about a block that was recently evicted. If a block is + * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough + * information to retrieve it from the L2ARC device. This information is + * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block + * that is in this state cannot access the data directly. + * + * Blocks that are actively being referenced or have not been evicted + * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within + * the arc_buf_hdr_t that will point to the data block in memory. A block can + * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC + * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and + * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd). + * + * The L1ARC's data pointer may or may not be uncompressed. The ARC has the + * ability to store the physical data (b_pabd) associated with the DVA of the + * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block, + * it will match its on-disk compression characteristics. This behavior can be + * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the + * compressed ARC functionality is disabled, the b_pabd will point to an + * uncompressed version of the on-disk data. + * + * Data in the L1ARC is not accessed by consumers of the ARC directly. Each + * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it. + * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC + * consumer. The ARC will provide references to this data and will keep it + * cached until it is no longer in use. The ARC caches only the L1ARC's physical + * data block and will evict any arc_buf_t that is no longer referenced. The + * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the + * "overhead_size" kstat. + * + * Depending on the consumer, an arc_buf_t can be requested in uncompressed or + * compressed form. The typical case is that consumers will want uncompressed + * data, and when that happens a new data buffer is allocated where the data is + * decompressed for them to use. Currently the only consumer who wants + * compressed arc_buf_t's is "zfs send", when it streams data exactly as it + * exists on disk. When this happens, the arc_buf_t's data buffer is shared + * with the arc_buf_hdr_t. + * + * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The + * first one is owned by a compressed send consumer (and therefore references + * the same compressed data buffer as the arc_buf_hdr_t) and the second could be + * used by any other consumer (and has its own uncompressed copy of the data + * buffer). + * + * arc_buf_hdr_t + * +-----------+ + * | fields | + * | common to | + * | L1- and | + * | L2ARC | + * +-----------+ + * | l2arc_buf_hdr_t + * | | + * +-----------+ + * | l1arc_buf_hdr_t + * | | arc_buf_t + * | b_buf +------------>+-----------+ arc_buf_t + * | b_pabd +-+ |b_next +---->+-----------+ + * +-----------+ | |-----------| |b_next +-->NULL + * | |b_comp = T | +-----------+ + * | |b_data +-+ |b_comp = F | + * | +-----------+ | |b_data +-+ + * +->+------+ | +-----------+ | + * compressed | | | | + * data | |<--------------+ | uncompressed + * +------+ compressed, | data + * shared +-->+------+ + * data | | + * | | + * +------+ + * + * When a consumer reads a block, the ARC must first look to see if the + * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new + * arc_buf_t and either copies uncompressed data into a new data buffer from an + * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a + * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the + * hdr is compressed and the desired compression characteristics of the + * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the + * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be + * the last buffer in the hdr's b_buf list, however a shared compressed buf can + * be anywhere in the hdr's list. + * + * The diagram below shows an example of an uncompressed ARC hdr that is + * sharing its data with an arc_buf_t (note that the shared uncompressed buf is + * the last element in the buf list): + * + * arc_buf_hdr_t + * +-----------+ + * | | + * | | + * | | + * +-----------+ + * l2arc_buf_hdr_t| | + * | | + * +-----------+ + * l1arc_buf_hdr_t| | + * | | arc_buf_t (shared) + * | b_buf +------------>+---------+ arc_buf_t + * | | |b_next +---->+---------+ + * | b_pabd +-+ |---------| |b_next +-->NULL + * +-----------+ | | | +---------+ + * | |b_data +-+ | | + * | +---------+ | |b_data +-+ + * +->+------+ | +---------+ | + * | | | | + * uncompressed | | | | + * data +------+ | | + * ^ +->+------+ | + * | uncompressed | | | + * | data | | | + * | +------+ | + * +---------------------------------+ + * + * Writing to the ARC requires that the ARC first discard the hdr's b_pabd + * since the physical block is about to be rewritten. The new data contents + * will be contained in the arc_buf_t. As the I/O pipeline performs the write, + * it may compress the data before writing it to disk. The ARC will be called + * with the transformed data and will bcopy the transformed on-disk block into + * a newly allocated b_pabd. Writes are always done into buffers which have + * either been loaned (and hence are new and don't have other readers) or + * buffers which have been released (and hence have their own hdr, if there + * were originally other readers of the buf's original hdr). This ensures that + * the ARC only needs to update a single buf and its hdr after a write occurs. + * + * When the L2ARC is in use, it will also take advantage of the b_pabd. The + * L2ARC will always write the contents of b_pabd to the L2ARC. This means + * that when compressed ARC is enabled that the L2ARC blocks are identical + * to the on-disk block in the main data pool. This provides a significant + * advantage since the ARC can leverage the bp's checksum when reading from the + * L2ARC to determine if the contents are valid. However, if the compressed + * ARC is disabled, then the L2ARC's block must be transformed to look + * like the physical block in the main data pool before comparing the + * checksum and determining its validity. + * + * The L1ARC has a slightly different system for storing encrypted data. + * Raw (encrypted + possibly compressed) data has a few subtle differences from + * data that is just compressed. The biggest difference is that it is not + * possible to decrypt encrypted data (or vice-versa) if the keys aren't loaded. + * The other difference is that encryption cannot be treated as a suggestion. + * If a caller would prefer compressed data, but they actually wind up with + * uncompressed data the worst thing that could happen is there might be a + * performance hit. If the caller requests encrypted data, however, we must be + * sure they actually get it or else secret information could be leaked. Raw + * data is stored in hdr->b_crypt_hdr.b_rabd. An encrypted header, therefore, + * may have both an encrypted version and a decrypted version of its data at + * once. When a caller needs a raw arc_buf_t, it is allocated and the data is + * copied out of this header. To avoid complications with b_pabd, raw buffers + * cannot be shared. + */ + +#include <sys/spa.h> +#include <sys/zio.h> +#include <sys/spa_impl.h> +#include <sys/zio_compress.h> +#include <sys/zio_checksum.h> +#include <sys/zfs_context.h> +#include <sys/arc.h> +#include <sys/zfs_refcount.h> +#include <sys/vdev.h> +#include <sys/vdev_impl.h> +#include <sys/dsl_pool.h> +#include <sys/zio_checksum.h> +#include <sys/multilist.h> +#include <sys/abd.h> +#include <sys/zil.h> +#include <sys/fm/fs/zfs.h> +#include <sys/callb.h> +#include <sys/kstat.h> +#include <sys/zthr.h> +#include <zfs_fletcher.h> +#include <sys/arc_impl.h> +#include <sys/trace_zfs.h> +#include <sys/aggsum.h> +#include <cityhash.h> +#include <sys/vdev_trim.h> + +#ifndef _KERNEL +/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ +boolean_t arc_watch = B_FALSE; +#endif + +/* + * This thread's job is to keep enough free memory in the system, by + * calling arc_kmem_reap_soon() plus arc_reduce_target_size(), which improves + * arc_available_memory(). + */ +static zthr_t *arc_reap_zthr; + +/* + * This thread's job is to keep arc_size under arc_c, by calling + * arc_evict(), which improves arc_is_overflowing(). + */ +static zthr_t *arc_evict_zthr; + +static kmutex_t arc_evict_lock; +static boolean_t arc_evict_needed = B_FALSE; + +/* + * Count of bytes evicted since boot. + */ +static uint64_t arc_evict_count; + +/* + * List of arc_evict_waiter_t's, representing threads waiting for the + * arc_evict_count to reach specific values. + */ +static list_t arc_evict_waiters; + +/* + * When arc_is_overflowing(), arc_get_data_impl() waits for this percent of + * the requested amount of data to be evicted. For example, by default for + * every 2KB that's evicted, 1KB of it may be "reused" by a new allocation. + * Since this is above 100%, it ensures that progress is made towards getting + * arc_size under arc_c. Since this is finite, it ensures that allocations + * can still happen, even during the potentially long time that arc_size is + * more than arc_c. + */ +int zfs_arc_eviction_pct = 200; + +/* + * The number of headers to evict in arc_evict_state_impl() before + * dropping the sublist lock and evicting from another sublist. A lower + * value means we're more likely to evict the "correct" header (i.e. the + * oldest header in the arc state), but comes with higher overhead + * (i.e. more invocations of arc_evict_state_impl()). + */ +int zfs_arc_evict_batch_limit = 10; + +/* number of seconds before growing cache again */ +int arc_grow_retry = 5; + +/* + * Minimum time between calls to arc_kmem_reap_soon(). + */ +int arc_kmem_cache_reap_retry_ms = 1000; + +/* shift of arc_c for calculating overflow limit in arc_get_data_impl */ +int zfs_arc_overflow_shift = 8; + +/* shift of arc_c for calculating both min and max arc_p */ +int arc_p_min_shift = 4; + +/* log2(fraction of arc to reclaim) */ +int arc_shrink_shift = 7; + +/* percent of pagecache to reclaim arc to */ +#ifdef _KERNEL +uint_t zfs_arc_pc_percent = 0; +#endif + +/* + * log2(fraction of ARC which must be free to allow growing). + * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, + * when reading a new block into the ARC, we will evict an equal-sized block + * from the ARC. + * + * This must be less than arc_shrink_shift, so that when we shrink the ARC, + * we will still not allow it to grow. + */ +int arc_no_grow_shift = 5; + + +/* + * minimum lifespan of a prefetch block in clock ticks + * (initialized in arc_init()) + */ +static int arc_min_prefetch_ms; +static int arc_min_prescient_prefetch_ms; + +/* + * If this percent of memory is free, don't throttle. + */ +int arc_lotsfree_percent = 10; + +/* + * The arc has filled available memory and has now warmed up. + */ +boolean_t arc_warm; + +/* + * These tunables are for performance analysis. + */ +unsigned long zfs_arc_max = 0; +unsigned long zfs_arc_min = 0; +unsigned long zfs_arc_meta_limit = 0; +unsigned long zfs_arc_meta_min = 0; +unsigned long zfs_arc_dnode_limit = 0; +unsigned long zfs_arc_dnode_reduce_percent = 10; +int zfs_arc_grow_retry = 0; +int zfs_arc_shrink_shift = 0; +int zfs_arc_p_min_shift = 0; +int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ + +/* + * ARC dirty data constraints for arc_tempreserve_space() throttle. + */ +unsigned long zfs_arc_dirty_limit_percent = 50; /* total dirty data limit */ +unsigned long zfs_arc_anon_limit_percent = 25; /* anon block dirty limit */ +unsigned long zfs_arc_pool_dirty_percent = 20; /* each pool's anon allowance */ + +/* + * Enable or disable compressed arc buffers. + */ +int zfs_compressed_arc_enabled = B_TRUE; + +/* + * ARC will evict meta buffers that exceed arc_meta_limit. This + * tunable make arc_meta_limit adjustable for different workloads. + */ +unsigned long zfs_arc_meta_limit_percent = 75; + +/* + * Percentage that can be consumed by dnodes of ARC meta buffers. + */ +unsigned long zfs_arc_dnode_limit_percent = 10; + +/* + * These tunables are Linux specific + */ +unsigned long zfs_arc_sys_free = 0; +int zfs_arc_min_prefetch_ms = 0; +int zfs_arc_min_prescient_prefetch_ms = 0; +int zfs_arc_p_dampener_disable = 1; +int zfs_arc_meta_prune = 10000; +int zfs_arc_meta_strategy = ARC_STRATEGY_META_BALANCED; +int zfs_arc_meta_adjust_restarts = 4096; +int zfs_arc_lotsfree_percent = 10; + +/* The 6 states: */ +arc_state_t ARC_anon; +arc_state_t ARC_mru; +arc_state_t ARC_mru_ghost; +arc_state_t ARC_mfu; +arc_state_t ARC_mfu_ghost; +arc_state_t ARC_l2c_only; + +arc_stats_t arc_stats = { + { "hits", KSTAT_DATA_UINT64 }, + { "misses", KSTAT_DATA_UINT64 }, + { "demand_data_hits", KSTAT_DATA_UINT64 }, + { "demand_data_misses", KSTAT_DATA_UINT64 }, + { "demand_metadata_hits", KSTAT_DATA_UINT64 }, + { "demand_metadata_misses", KSTAT_DATA_UINT64 }, + { "prefetch_data_hits", KSTAT_DATA_UINT64 }, + { "prefetch_data_misses", KSTAT_DATA_UINT64 }, + { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, + { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, + { "mru_hits", KSTAT_DATA_UINT64 }, + { "mru_ghost_hits", KSTAT_DATA_UINT64 }, + { "mfu_hits", KSTAT_DATA_UINT64 }, + { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, + { "deleted", KSTAT_DATA_UINT64 }, + { "mutex_miss", KSTAT_DATA_UINT64 }, + { "access_skip", KSTAT_DATA_UINT64 }, + { "evict_skip", KSTAT_DATA_UINT64 }, + { "evict_not_enough", KSTAT_DATA_UINT64 }, + { "evict_l2_cached", KSTAT_DATA_UINT64 }, + { "evict_l2_eligible", KSTAT_DATA_UINT64 }, + { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, + { "evict_l2_skip", KSTAT_DATA_UINT64 }, + { "hash_elements", KSTAT_DATA_UINT64 }, + { "hash_elements_max", KSTAT_DATA_UINT64 }, + { "hash_collisions", KSTAT_DATA_UINT64 }, + { "hash_chains", KSTAT_DATA_UINT64 }, + { "hash_chain_max", KSTAT_DATA_UINT64 }, + { "p", KSTAT_DATA_UINT64 }, + { "c", KSTAT_DATA_UINT64 }, + { "c_min", KSTAT_DATA_UINT64 }, + { "c_max", KSTAT_DATA_UINT64 }, + { "size", KSTAT_DATA_UINT64 }, + { "compressed_size", KSTAT_DATA_UINT64 }, + { "uncompressed_size", KSTAT_DATA_UINT64 }, + { "overhead_size", KSTAT_DATA_UINT64 }, + { "hdr_size", KSTAT_DATA_UINT64 }, + { "data_size", KSTAT_DATA_UINT64 }, + { "metadata_size", KSTAT_DATA_UINT64 }, + { "dbuf_size", KSTAT_DATA_UINT64 }, + { "dnode_size", KSTAT_DATA_UINT64 }, + { "bonus_size", KSTAT_DATA_UINT64 }, +#if defined(COMPAT_FREEBSD11) + { "other_size", KSTAT_DATA_UINT64 }, +#endif + { "anon_size", KSTAT_DATA_UINT64 }, + { "anon_evictable_data", KSTAT_DATA_UINT64 }, + { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, + { "mru_size", KSTAT_DATA_UINT64 }, + { "mru_evictable_data", KSTAT_DATA_UINT64 }, + { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, + { "mru_ghost_size", KSTAT_DATA_UINT64 }, + { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, + { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, + { "mfu_size", KSTAT_DATA_UINT64 }, + { "mfu_evictable_data", KSTAT_DATA_UINT64 }, + { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, + { "mfu_ghost_size", KSTAT_DATA_UINT64 }, + { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, + { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, + { "l2_hits", KSTAT_DATA_UINT64 }, + { "l2_misses", KSTAT_DATA_UINT64 }, + { "l2_feeds", KSTAT_DATA_UINT64 }, + { "l2_rw_clash", KSTAT_DATA_UINT64 }, + { "l2_read_bytes", KSTAT_DATA_UINT64 }, + { "l2_write_bytes", KSTAT_DATA_UINT64 }, + { "l2_writes_sent", KSTAT_DATA_UINT64 }, + { "l2_writes_done", KSTAT_DATA_UINT64 }, + { "l2_writes_error", KSTAT_DATA_UINT64 }, + { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, + { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, + { "l2_evict_reading", KSTAT_DATA_UINT64 }, + { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, + { "l2_free_on_write", KSTAT_DATA_UINT64 }, + { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, + { "l2_cksum_bad", KSTAT_DATA_UINT64 }, + { "l2_io_error", KSTAT_DATA_UINT64 }, + { "l2_size", KSTAT_DATA_UINT64 }, + { "l2_asize", KSTAT_DATA_UINT64 }, + { "l2_hdr_size", KSTAT_DATA_UINT64 }, + { "l2_log_blk_writes", KSTAT_DATA_UINT64 }, + { "l2_log_blk_avg_asize", KSTAT_DATA_UINT64 }, + { "l2_log_blk_asize", KSTAT_DATA_UINT64 }, + { "l2_log_blk_count", KSTAT_DATA_UINT64 }, + { "l2_data_to_meta_ratio", KSTAT_DATA_UINT64 }, + { "l2_rebuild_success", KSTAT_DATA_UINT64 }, + { "l2_rebuild_unsupported", KSTAT_DATA_UINT64 }, + { "l2_rebuild_io_errors", KSTAT_DATA_UINT64 }, + { "l2_rebuild_dh_errors", KSTAT_DATA_UINT64 }, + { "l2_rebuild_cksum_lb_errors", KSTAT_DATA_UINT64 }, + { "l2_rebuild_lowmem", KSTAT_DATA_UINT64 }, + { "l2_rebuild_size", KSTAT_DATA_UINT64 }, + { "l2_rebuild_asize", KSTAT_DATA_UINT64 }, + { "l2_rebuild_bufs", KSTAT_DATA_UINT64 }, + { "l2_rebuild_bufs_precached", KSTAT_DATA_UINT64 }, + { "l2_rebuild_log_blks", KSTAT_DATA_UINT64 }, + { "memory_throttle_count", KSTAT_DATA_UINT64 }, + { "memory_direct_count", KSTAT_DATA_UINT64 }, + { "memory_indirect_count", KSTAT_DATA_UINT64 }, + { "memory_all_bytes", KSTAT_DATA_UINT64 }, + { "memory_free_bytes", KSTAT_DATA_UINT64 }, + { "memory_available_bytes", KSTAT_DATA_INT64 }, + { "arc_no_grow", KSTAT_DATA_UINT64 }, + { "arc_tempreserve", KSTAT_DATA_UINT64 }, + { "arc_loaned_bytes", KSTAT_DATA_UINT64 }, + { "arc_prune", KSTAT_DATA_UINT64 }, + { "arc_meta_used", KSTAT_DATA_UINT64 }, + { "arc_meta_limit", KSTAT_DATA_UINT64 }, + { "arc_dnode_limit", KSTAT_DATA_UINT64 }, + { "arc_meta_max", KSTAT_DATA_UINT64 }, + { "arc_meta_min", KSTAT_DATA_UINT64 }, + { "async_upgrade_sync", KSTAT_DATA_UINT64 }, + { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, + { "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 }, + { "arc_need_free", KSTAT_DATA_UINT64 }, + { "arc_sys_free", KSTAT_DATA_UINT64 }, + { "arc_raw_size", KSTAT_DATA_UINT64 }, + { "cached_only_in_progress", KSTAT_DATA_UINT64 }, + { "abd_chunk_waste_size", KSTAT_DATA_UINT64 }, +}; + +#define ARCSTAT_MAX(stat, val) { \ + uint64_t m; \ + while ((val) > (m = arc_stats.stat.value.ui64) && \ + (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ + continue; \ +} + +#define ARCSTAT_MAXSTAT(stat) \ + ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) + +/* + * We define a macro to allow ARC hits/misses to be easily broken down by + * two separate conditions, giving a total of four different subtypes for + * each of hits and misses (so eight statistics total). + */ +#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ + if (cond1) { \ + if (cond2) { \ + ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ + } else { \ + ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ + } \ + } else { \ + if (cond2) { \ + ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ + } else { \ + ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ + } \ + } + +/* + * This macro allows us to use kstats as floating averages. Each time we + * update this kstat, we first factor it and the update value by + * ARCSTAT_AVG_FACTOR to shrink the new value's contribution to the overall + * average. This macro assumes that integer loads and stores are atomic, but + * is not safe for multiple writers updating the kstat in parallel (only the + * last writer's update will remain). + */ +#define ARCSTAT_F_AVG_FACTOR 3 +#define ARCSTAT_F_AVG(stat, value) \ + do { \ + uint64_t x = ARCSTAT(stat); \ + x = x - x / ARCSTAT_F_AVG_FACTOR + \ + (value) / ARCSTAT_F_AVG_FACTOR; \ + ARCSTAT(stat) = x; \ + _NOTE(CONSTCOND) \ + } while (0) + +kstat_t *arc_ksp; +static arc_state_t *arc_anon; +static arc_state_t *arc_mru_ghost; +static arc_state_t *arc_mfu_ghost; +static arc_state_t *arc_l2c_only; + +arc_state_t *arc_mru; +arc_state_t *arc_mfu; + +/* + * There are several ARC variables that are critical to export as kstats -- + * but we don't want to have to grovel around in the kstat whenever we wish to + * manipulate them. For these variables, we therefore define them to be in + * terms of the statistic variable. This assures that we are not introducing + * the possibility of inconsistency by having shadow copies of the variables, + * while still allowing the code to be readable. + */ +#define arc_tempreserve ARCSTAT(arcstat_tempreserve) +#define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes) +#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ +/* max size for dnodes */ +#define arc_dnode_size_limit ARCSTAT(arcstat_dnode_limit) +#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ +#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ +#define arc_need_free ARCSTAT(arcstat_need_free) /* waiting to be evicted */ + +/* size of all b_rabd's in entire arc */ +#define arc_raw_size ARCSTAT(arcstat_raw_size) +/* compressed size of entire arc */ +#define arc_compressed_size ARCSTAT(arcstat_compressed_size) +/* uncompressed size of entire arc */ +#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) +/* number of bytes in the arc from arc_buf_t's */ +#define arc_overhead_size ARCSTAT(arcstat_overhead_size) + +/* + * There are also some ARC variables that we want to export, but that are + * updated so often that having the canonical representation be the statistic + * variable causes a performance bottleneck. We want to use aggsum_t's for these + * instead, but still be able to export the kstat in the same way as before. + * The solution is to always use the aggsum version, except in the kstat update + * callback. + */ +aggsum_t arc_size; +aggsum_t arc_meta_used; +aggsum_t astat_data_size; +aggsum_t astat_metadata_size; +aggsum_t astat_dbuf_size; +aggsum_t astat_dnode_size; +aggsum_t astat_bonus_size; +aggsum_t astat_hdr_size; +aggsum_t astat_l2_hdr_size; +aggsum_t astat_abd_chunk_waste_size; + +hrtime_t arc_growtime; +list_t arc_prune_list; +kmutex_t arc_prune_mtx; +taskq_t *arc_prune_taskq; + +#define GHOST_STATE(state) \ + ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ + (state) == arc_l2c_only) + +#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) +#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) +#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) +#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) +#define HDR_PRESCIENT_PREFETCH(hdr) \ + ((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) +#define HDR_COMPRESSION_ENABLED(hdr) \ + ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) + +#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) +#define HDR_L2_READING(hdr) \ + (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ + ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) +#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) +#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) +#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) +#define HDR_PROTECTED(hdr) ((hdr)->b_flags & ARC_FLAG_PROTECTED) +#define HDR_NOAUTH(hdr) ((hdr)->b_flags & ARC_FLAG_NOAUTH) +#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) + +#define HDR_ISTYPE_METADATA(hdr) \ + ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) +#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) + +#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) +#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) +#define HDR_HAS_RABD(hdr) \ + (HDR_HAS_L1HDR(hdr) && HDR_PROTECTED(hdr) && \ + (hdr)->b_crypt_hdr.b_rabd != NULL) +#define HDR_ENCRYPTED(hdr) \ + (HDR_PROTECTED(hdr) && DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot)) +#define HDR_AUTHENTICATED(hdr) \ + (HDR_PROTECTED(hdr) && !DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot)) + +/* For storing compression mode in b_flags */ +#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) + +#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ + HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) +#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ + HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); + +#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) +#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED) +#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED) +#define ARC_BUF_ENCRYPTED(buf) ((buf)->b_flags & ARC_BUF_FLAG_ENCRYPTED) + +/* + * Other sizes + */ + +#define HDR_FULL_CRYPT_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) +#define HDR_FULL_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_crypt_hdr)) +#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) + +/* + * Hash table routines + */ + +#define HT_LOCK_ALIGN 64 +#define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN))) + +struct ht_lock { + kmutex_t ht_lock; +#ifdef _KERNEL + unsigned char pad[HT_LOCK_PAD]; +#endif +}; + +#define BUF_LOCKS 8192 +typedef struct buf_hash_table { + uint64_t ht_mask; + arc_buf_hdr_t **ht_table; + struct ht_lock ht_locks[BUF_LOCKS]; +} buf_hash_table_t; + +static buf_hash_table_t buf_hash_table; + +#define BUF_HASH_INDEX(spa, dva, birth) \ + (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) +#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) +#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) +#define HDR_LOCK(hdr) \ + (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) + +uint64_t zfs_crc64_table[256]; + +/* + * Level 2 ARC + */ + +#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ +#define L2ARC_HEADROOM 2 /* num of writes */ + +/* + * If we discover during ARC scan any buffers to be compressed, we boost + * our headroom for the next scanning cycle by this percentage multiple. + */ +#define L2ARC_HEADROOM_BOOST 200 +#define L2ARC_FEED_SECS 1 /* caching interval secs */ +#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ + +/* + * We can feed L2ARC from two states of ARC buffers, mru and mfu, + * and each of the state has two types: data and metadata. + */ +#define L2ARC_FEED_TYPES 4 + +#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) +#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) + +/* L2ARC Performance Tunables */ +unsigned long l2arc_write_max = L2ARC_WRITE_SIZE; /* def max write size */ +unsigned long l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra warmup write */ +unsigned long l2arc_headroom = L2ARC_HEADROOM; /* # of dev writes */ +unsigned long l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; +unsigned long l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ +unsigned long l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval msecs */ +int l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ +int l2arc_feed_again = B_TRUE; /* turbo warmup */ +int l2arc_norw = B_FALSE; /* no reads during writes */ + +/* + * L2ARC Internals + */ +static list_t L2ARC_dev_list; /* device list */ +static list_t *l2arc_dev_list; /* device list pointer */ +static kmutex_t l2arc_dev_mtx; /* device list mutex */ +static l2arc_dev_t *l2arc_dev_last; /* last device used */ +static list_t L2ARC_free_on_write; /* free after write buf list */ +static list_t *l2arc_free_on_write; /* free after write list ptr */ +static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ +static uint64_t l2arc_ndev; /* number of devices */ + +typedef struct l2arc_read_callback { + arc_buf_hdr_t *l2rcb_hdr; /* read header */ + blkptr_t l2rcb_bp; /* original blkptr */ + zbookmark_phys_t l2rcb_zb; /* original bookmark */ + int l2rcb_flags; /* original flags */ + abd_t *l2rcb_abd; /* temporary buffer */ +} l2arc_read_callback_t; + +typedef struct l2arc_data_free { + /* protected by l2arc_free_on_write_mtx */ + abd_t *l2df_abd; + size_t l2df_size; + arc_buf_contents_t l2df_type; + list_node_t l2df_list_node; +} l2arc_data_free_t; + +typedef enum arc_fill_flags { + ARC_FILL_LOCKED = 1 << 0, /* hdr lock is held */ + ARC_FILL_COMPRESSED = 1 << 1, /* fill with compressed data */ + ARC_FILL_ENCRYPTED = 1 << 2, /* fill with encrypted data */ + ARC_FILL_NOAUTH = 1 << 3, /* don't attempt to authenticate */ + ARC_FILL_IN_PLACE = 1 << 4 /* fill in place (special case) */ +} arc_fill_flags_t; + +static kmutex_t l2arc_feed_thr_lock; +static kcondvar_t l2arc_feed_thr_cv; +static uint8_t l2arc_thread_exit; + +static kmutex_t l2arc_rebuild_thr_lock; +static kcondvar_t l2arc_rebuild_thr_cv; + +enum arc_hdr_alloc_flags { + ARC_HDR_ALLOC_RDATA = 0x1, + ARC_HDR_DO_ADAPT = 0x2, +}; + + +static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *, boolean_t); +static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); +static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *, boolean_t); +static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *); +static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); +static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag); +static void arc_hdr_free_abd(arc_buf_hdr_t *, boolean_t); +static void arc_hdr_alloc_abd(arc_buf_hdr_t *, int); +static void arc_access(arc_buf_hdr_t *, kmutex_t *); +static void arc_buf_watch(arc_buf_t *); + +static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); +static uint32_t arc_bufc_to_flags(arc_buf_contents_t); +static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); +static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); + +static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); +static void l2arc_read_done(zio_t *); +static void l2arc_do_free_on_write(void); + +/* + * L2ARC TRIM + * l2arc_trim_ahead : A ZFS module parameter that controls how much ahead of + * the current write size (l2arc_write_max) we should TRIM if we + * have filled the device. It is defined as a percentage of the + * write size. If set to 100 we trim twice the space required to + * accommodate upcoming writes. A minimum of 64MB will be trimmed. + * It also enables TRIM of the whole L2ARC device upon creation or + * addition to an existing pool or if the header of the device is + * invalid upon importing a pool or onlining a cache device. The + * default is 0, which disables TRIM on L2ARC altogether as it can + * put significant stress on the underlying storage devices. This + * will vary depending of how well the specific device handles + * these commands. + */ +unsigned long l2arc_trim_ahead = 0; + +/* + * Performance tuning of L2ARC persistence: + * + * l2arc_rebuild_enabled : A ZFS module parameter that controls whether adding + * an L2ARC device (either at pool import or later) will attempt + * to rebuild L2ARC buffer contents. + * l2arc_rebuild_blocks_min_l2size : A ZFS module parameter that controls + * whether log blocks are written to the L2ARC device. If the L2ARC + * device is less than 1GB, the amount of data l2arc_evict() + * evicts is significant compared to the amount of restored L2ARC + * data. In this case do not write log blocks in L2ARC in order + * not to waste space. + */ +int l2arc_rebuild_enabled = B_TRUE; +unsigned long l2arc_rebuild_blocks_min_l2size = 1024 * 1024 * 1024; + +/* L2ARC persistence rebuild control routines. */ +void l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen); +static void l2arc_dev_rebuild_thread(void *arg); +static int l2arc_rebuild(l2arc_dev_t *dev); + +/* L2ARC persistence read I/O routines. */ +static int l2arc_dev_hdr_read(l2arc_dev_t *dev); +static int l2arc_log_blk_read(l2arc_dev_t *dev, + const l2arc_log_blkptr_t *this_lp, const l2arc_log_blkptr_t *next_lp, + l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb, + zio_t *this_io, zio_t **next_io); +static zio_t *l2arc_log_blk_fetch(vdev_t *vd, + const l2arc_log_blkptr_t *lp, l2arc_log_blk_phys_t *lb); +static void l2arc_log_blk_fetch_abort(zio_t *zio); + +/* L2ARC persistence block restoration routines. */ +static void l2arc_log_blk_restore(l2arc_dev_t *dev, + const l2arc_log_blk_phys_t *lb, uint64_t lb_asize, uint64_t lb_daddr); +static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, + l2arc_dev_t *dev); + +/* L2ARC persistence write I/O routines. */ +static void l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, + l2arc_write_callback_t *cb); + +/* L2ARC persistence auxiliary routines. */ +boolean_t l2arc_log_blkptr_valid(l2arc_dev_t *dev, + const l2arc_log_blkptr_t *lbp); +static boolean_t l2arc_log_blk_insert(l2arc_dev_t *dev, + const arc_buf_hdr_t *ab); +boolean_t l2arc_range_check_overlap(uint64_t bottom, + uint64_t top, uint64_t check); +static void l2arc_blk_fetch_done(zio_t *zio); +static inline uint64_t + l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev); + +/* + * We use Cityhash for this. It's fast, and has good hash properties without + * requiring any large static buffers. + */ +static uint64_t +buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) +{ + return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth)); +} + +#define HDR_EMPTY(hdr) \ + ((hdr)->b_dva.dva_word[0] == 0 && \ + (hdr)->b_dva.dva_word[1] == 0) + +#define HDR_EMPTY_OR_LOCKED(hdr) \ + (HDR_EMPTY(hdr) || MUTEX_HELD(HDR_LOCK(hdr))) + +#define HDR_EQUAL(spa, dva, birth, hdr) \ + ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ + ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ + ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) + +static void +buf_discard_identity(arc_buf_hdr_t *hdr) +{ + hdr->b_dva.dva_word[0] = 0; + hdr->b_dva.dva_word[1] = 0; + hdr->b_birth = 0; +} + +static arc_buf_hdr_t * +buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) +{ + const dva_t *dva = BP_IDENTITY(bp); + uint64_t birth = BP_PHYSICAL_BIRTH(bp); + uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); + kmutex_t *hash_lock = BUF_HASH_LOCK(idx); + arc_buf_hdr_t *hdr; + + mutex_enter(hash_lock); + for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; + hdr = hdr->b_hash_next) { + if (HDR_EQUAL(spa, dva, birth, hdr)) { + *lockp = hash_lock; + return (hdr); + } + } + mutex_exit(hash_lock); + *lockp = NULL; + return (NULL); +} + +/* + * Insert an entry into the hash table. If there is already an element + * equal to elem in the hash table, then the already existing element + * will be returned and the new element will not be inserted. + * Otherwise returns NULL. + * If lockp == NULL, the caller is assumed to already hold the hash lock. + */ +static arc_buf_hdr_t * +buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) +{ + uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); + kmutex_t *hash_lock = BUF_HASH_LOCK(idx); + arc_buf_hdr_t *fhdr; + uint32_t i; + + ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); + ASSERT(hdr->b_birth != 0); + ASSERT(!HDR_IN_HASH_TABLE(hdr)); + + if (lockp != NULL) { + *lockp = hash_lock; + mutex_enter(hash_lock); + } else { + ASSERT(MUTEX_HELD(hash_lock)); + } + + for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; + fhdr = fhdr->b_hash_next, i++) { + if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) + return (fhdr); + } + + hdr->b_hash_next = buf_hash_table.ht_table[idx]; + buf_hash_table.ht_table[idx] = hdr; + arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); + + /* collect some hash table performance data */ + if (i > 0) { + ARCSTAT_BUMP(arcstat_hash_collisions); + if (i == 1) + ARCSTAT_BUMP(arcstat_hash_chains); + + ARCSTAT_MAX(arcstat_hash_chain_max, i); + } + + ARCSTAT_BUMP(arcstat_hash_elements); + ARCSTAT_MAXSTAT(arcstat_hash_elements); + + return (NULL); +} + +static void +buf_hash_remove(arc_buf_hdr_t *hdr) +{ + arc_buf_hdr_t *fhdr, **hdrp; + uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); + + ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); + ASSERT(HDR_IN_HASH_TABLE(hdr)); + + hdrp = &buf_hash_table.ht_table[idx]; + while ((fhdr = *hdrp) != hdr) { + ASSERT3P(fhdr, !=, NULL); + hdrp = &fhdr->b_hash_next; + } + *hdrp = hdr->b_hash_next; + hdr->b_hash_next = NULL; + arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); + + /* collect some hash table performance data */ + ARCSTAT_BUMPDOWN(arcstat_hash_elements); + + if (buf_hash_table.ht_table[idx] && + buf_hash_table.ht_table[idx]->b_hash_next == NULL) + ARCSTAT_BUMPDOWN(arcstat_hash_chains); +} + +/* + * Global data structures and functions for the buf kmem cache. + */ + +static kmem_cache_t *hdr_full_cache; +static kmem_cache_t *hdr_full_crypt_cache; +static kmem_cache_t *hdr_l2only_cache; +static kmem_cache_t *buf_cache; + +static void +buf_fini(void) +{ + int i; + +#if defined(_KERNEL) + /* + * Large allocations which do not require contiguous pages + * should be using vmem_free() in the linux kernel\ + */ + vmem_free(buf_hash_table.ht_table, + (buf_hash_table.ht_mask + 1) * sizeof (void *)); +#else + kmem_free(buf_hash_table.ht_table, + (buf_hash_table.ht_mask + 1) * sizeof (void *)); +#endif + for (i = 0; i < BUF_LOCKS; i++) + mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); + kmem_cache_destroy(hdr_full_cache); + kmem_cache_destroy(hdr_full_crypt_cache); + kmem_cache_destroy(hdr_l2only_cache); + kmem_cache_destroy(buf_cache); +} + +/* + * Constructor callback - called when the cache is empty + * and a new buf is requested. + */ +/* ARGSUSED */ +static int +hdr_full_cons(void *vbuf, void *unused, int kmflag) +{ + arc_buf_hdr_t *hdr = vbuf; + + bzero(hdr, HDR_FULL_SIZE); + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; + cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); + zfs_refcount_create(&hdr->b_l1hdr.b_refcnt); + mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); + list_link_init(&hdr->b_l1hdr.b_arc_node); + list_link_init(&hdr->b_l2hdr.b_l2node); + multilist_link_init(&hdr->b_l1hdr.b_arc_node); + arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); + + return (0); +} + +/* ARGSUSED */ +static int +hdr_full_crypt_cons(void *vbuf, void *unused, int kmflag) +{ + arc_buf_hdr_t *hdr = vbuf; + + hdr_full_cons(vbuf, unused, kmflag); + bzero(&hdr->b_crypt_hdr, sizeof (hdr->b_crypt_hdr)); + arc_space_consume(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS); + + return (0); +} + +/* ARGSUSED */ +static int +hdr_l2only_cons(void *vbuf, void *unused, int kmflag) +{ + arc_buf_hdr_t *hdr = vbuf; + + bzero(hdr, HDR_L2ONLY_SIZE); + arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); + + return (0); +} + +/* ARGSUSED */ +static int +buf_cons(void *vbuf, void *unused, int kmflag) +{ + arc_buf_t *buf = vbuf; + + bzero(buf, sizeof (arc_buf_t)); + mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); + arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); + + return (0); +} + +/* + * Destructor callback - called when a cached buf is + * no longer required. + */ +/* ARGSUSED */ +static void +hdr_full_dest(void *vbuf, void *unused) +{ + arc_buf_hdr_t *hdr = vbuf; + + ASSERT(HDR_EMPTY(hdr)); + cv_destroy(&hdr->b_l1hdr.b_cv); + zfs_refcount_destroy(&hdr->b_l1hdr.b_refcnt); + mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); + ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); + arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); +} + +/* ARGSUSED */ +static void +hdr_full_crypt_dest(void *vbuf, void *unused) +{ + arc_buf_hdr_t *hdr = vbuf; + + hdr_full_dest(vbuf, unused); + arc_space_return(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS); +} + +/* ARGSUSED */ +static void +hdr_l2only_dest(void *vbuf, void *unused) +{ + arc_buf_hdr_t *hdr __maybe_unused = vbuf; + + ASSERT(HDR_EMPTY(hdr)); + arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); +} + +/* ARGSUSED */ +static void +buf_dest(void *vbuf, void *unused) +{ + arc_buf_t *buf = vbuf; + + mutex_destroy(&buf->b_evict_lock); + arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); +} + +static void +buf_init(void) +{ + uint64_t *ct = NULL; + uint64_t hsize = 1ULL << 12; + int i, j; + + /* + * The hash table is big enough to fill all of physical memory + * with an average block size of zfs_arc_average_blocksize (default 8K). + * By default, the table will take up + * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). + */ + while (hsize * zfs_arc_average_blocksize < arc_all_memory()) + hsize <<= 1; +retry: + buf_hash_table.ht_mask = hsize - 1; +#if defined(_KERNEL) + /* + * Large allocations which do not require contiguous pages + * should be using vmem_alloc() in the linux kernel + */ + buf_hash_table.ht_table = + vmem_zalloc(hsize * sizeof (void*), KM_SLEEP); +#else + buf_hash_table.ht_table = + kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); +#endif + if (buf_hash_table.ht_table == NULL) { + ASSERT(hsize > (1ULL << 8)); + hsize >>= 1; + goto retry; + } + + hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, + 0, hdr_full_cons, hdr_full_dest, NULL, NULL, NULL, 0); + hdr_full_crypt_cache = kmem_cache_create("arc_buf_hdr_t_full_crypt", + HDR_FULL_CRYPT_SIZE, 0, hdr_full_crypt_cons, hdr_full_crypt_dest, + NULL, NULL, NULL, 0); + hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", + HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, NULL, + NULL, NULL, 0); + buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), + 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); + + for (i = 0; i < 256; i++) + for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) + *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); + + for (i = 0; i < BUF_LOCKS; i++) { + mutex_init(&buf_hash_table.ht_locks[i].ht_lock, + NULL, MUTEX_DEFAULT, NULL); + } +} + +#define ARC_MINTIME (hz>>4) /* 62 ms */ + +/* + * This is the size that the buf occupies in memory. If the buf is compressed, + * it will correspond to the compressed size. You should use this method of + * getting the buf size unless you explicitly need the logical size. + */ +uint64_t +arc_buf_size(arc_buf_t *buf) +{ + return (ARC_BUF_COMPRESSED(buf) ? + HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr)); +} + +uint64_t +arc_buf_lsize(arc_buf_t *buf) +{ + return (HDR_GET_LSIZE(buf->b_hdr)); +} + +/* + * This function will return B_TRUE if the buffer is encrypted in memory. + * This buffer can be decrypted by calling arc_untransform(). + */ +boolean_t +arc_is_encrypted(arc_buf_t *buf) +{ + return (ARC_BUF_ENCRYPTED(buf) != 0); +} + +/* + * Returns B_TRUE if the buffer represents data that has not had its MAC + * verified yet. + */ +boolean_t +arc_is_unauthenticated(arc_buf_t *buf) +{ + return (HDR_NOAUTH(buf->b_hdr) != 0); +} + +void +arc_get_raw_params(arc_buf_t *buf, boolean_t *byteorder, uint8_t *salt, + uint8_t *iv, uint8_t *mac) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + ASSERT(HDR_PROTECTED(hdr)); + + bcopy(hdr->b_crypt_hdr.b_salt, salt, ZIO_DATA_SALT_LEN); + bcopy(hdr->b_crypt_hdr.b_iv, iv, ZIO_DATA_IV_LEN); + bcopy(hdr->b_crypt_hdr.b_mac, mac, ZIO_DATA_MAC_LEN); + *byteorder = (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ? + ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER; +} + +/* + * Indicates how this buffer is compressed in memory. If it is not compressed + * the value will be ZIO_COMPRESS_OFF. It can be made normally readable with + * arc_untransform() as long as it is also unencrypted. + */ +enum zio_compress +arc_get_compression(arc_buf_t *buf) +{ + return (ARC_BUF_COMPRESSED(buf) ? + HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF); +} + +/* + * Return the compression algorithm used to store this data in the ARC. If ARC + * compression is enabled or this is an encrypted block, this will be the same + * as what's used to store it on-disk. Otherwise, this will be ZIO_COMPRESS_OFF. + */ +static inline enum zio_compress +arc_hdr_get_compress(arc_buf_hdr_t *hdr) +{ + return (HDR_COMPRESSION_ENABLED(hdr) ? + HDR_GET_COMPRESS(hdr) : ZIO_COMPRESS_OFF); +} + +uint8_t +arc_get_complevel(arc_buf_t *buf) +{ + return (buf->b_hdr->b_complevel); +} + +static inline boolean_t +arc_buf_is_shared(arc_buf_t *buf) +{ + boolean_t shared = (buf->b_data != NULL && + buf->b_hdr->b_l1hdr.b_pabd != NULL && + abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) && + buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd)); + IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); + IMPLY(shared, ARC_BUF_SHARED(buf)); + IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf)); + + /* + * It would be nice to assert arc_can_share() too, but the "hdr isn't + * already being shared" requirement prevents us from doing that. + */ + + return (shared); +} + +/* + * Free the checksum associated with this header. If there is no checksum, this + * is a no-op. + */ +static inline void +arc_cksum_free(arc_buf_hdr_t *hdr) +{ + ASSERT(HDR_HAS_L1HDR(hdr)); + + mutex_enter(&hdr->b_l1hdr.b_freeze_lock); + if (hdr->b_l1hdr.b_freeze_cksum != NULL) { + kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); + hdr->b_l1hdr.b_freeze_cksum = NULL; + } + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); +} + +/* + * Return true iff at least one of the bufs on hdr is not compressed. + * Encrypted buffers count as compressed. + */ +static boolean_t +arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr) +{ + ASSERT(hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY_OR_LOCKED(hdr)); + + for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) { + if (!ARC_BUF_COMPRESSED(b)) { + return (B_TRUE); + } + } + return (B_FALSE); +} + + +/* + * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data + * matches the checksum that is stored in the hdr. If there is no checksum, + * or if the buf is compressed, this is a no-op. + */ +static void +arc_cksum_verify(arc_buf_t *buf) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + zio_cksum_t zc; + + if (!(zfs_flags & ZFS_DEBUG_MODIFY)) + return; + + if (ARC_BUF_COMPRESSED(buf)) + return; + + ASSERT(HDR_HAS_L1HDR(hdr)); + + mutex_enter(&hdr->b_l1hdr.b_freeze_lock); + + if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); + return; + } + + fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc); + if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) + panic("buffer modified while frozen!"); + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); +} + +/* + * This function makes the assumption that data stored in the L2ARC + * will be transformed exactly as it is in the main pool. Because of + * this we can verify the checksum against the reading process's bp. + */ +static boolean_t +arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) +{ + ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); + VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); + + /* + * Block pointers always store the checksum for the logical data. + * If the block pointer has the gang bit set, then the checksum + * it represents is for the reconstituted data and not for an + * individual gang member. The zio pipeline, however, must be able to + * determine the checksum of each of the gang constituents so it + * treats the checksum comparison differently than what we need + * for l2arc blocks. This prevents us from using the + * zio_checksum_error() interface directly. Instead we must call the + * zio_checksum_error_impl() so that we can ensure the checksum is + * generated using the correct checksum algorithm and accounts for the + * logical I/O size and not just a gang fragment. + */ + return (zio_checksum_error_impl(zio->io_spa, zio->io_bp, + BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size, + zio->io_offset, NULL) == 0); +} + +/* + * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a + * checksum and attaches it to the buf's hdr so that we can ensure that the buf + * isn't modified later on. If buf is compressed or there is already a checksum + * on the hdr, this is a no-op (we only checksum uncompressed bufs). + */ +static void +arc_cksum_compute(arc_buf_t *buf) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + if (!(zfs_flags & ZFS_DEBUG_MODIFY)) + return; + + ASSERT(HDR_HAS_L1HDR(hdr)); + + mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); + if (hdr->b_l1hdr.b_freeze_cksum != NULL || ARC_BUF_COMPRESSED(buf)) { + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); + return; + } + + ASSERT(!ARC_BUF_ENCRYPTED(buf)); + ASSERT(!ARC_BUF_COMPRESSED(buf)); + hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), + KM_SLEEP); + fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, + hdr->b_l1hdr.b_freeze_cksum); + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); + arc_buf_watch(buf); +} + +#ifndef _KERNEL +void +arc_buf_sigsegv(int sig, siginfo_t *si, void *unused) +{ + panic("Got SIGSEGV at address: 0x%lx\n", (long)si->si_addr); +} +#endif + +/* ARGSUSED */ +static void +arc_buf_unwatch(arc_buf_t *buf) +{ +#ifndef _KERNEL + if (arc_watch) { + ASSERT0(mprotect(buf->b_data, arc_buf_size(buf), + PROT_READ | PROT_WRITE)); + } +#endif +} + +/* ARGSUSED */ +static void +arc_buf_watch(arc_buf_t *buf) +{ +#ifndef _KERNEL + if (arc_watch) + ASSERT0(mprotect(buf->b_data, arc_buf_size(buf), + PROT_READ)); +#endif +} + +static arc_buf_contents_t +arc_buf_type(arc_buf_hdr_t *hdr) +{ + arc_buf_contents_t type; + if (HDR_ISTYPE_METADATA(hdr)) { + type = ARC_BUFC_METADATA; + } else { + type = ARC_BUFC_DATA; + } + VERIFY3U(hdr->b_type, ==, type); + return (type); +} + +boolean_t +arc_is_metadata(arc_buf_t *buf) +{ + return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0); +} + +static uint32_t +arc_bufc_to_flags(arc_buf_contents_t type) +{ + switch (type) { + case ARC_BUFC_DATA: + /* metadata field is 0 if buffer contains normal data */ + return (0); + case ARC_BUFC_METADATA: + return (ARC_FLAG_BUFC_METADATA); + default: + break; + } + panic("undefined ARC buffer type!"); + return ((uint32_t)-1); +} + +void +arc_buf_thaw(arc_buf_t *buf) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + + arc_cksum_verify(buf); + + /* + * Compressed buffers do not manipulate the b_freeze_cksum. + */ + if (ARC_BUF_COMPRESSED(buf)) + return; + + ASSERT(HDR_HAS_L1HDR(hdr)); + arc_cksum_free(hdr); + arc_buf_unwatch(buf); +} + +void +arc_buf_freeze(arc_buf_t *buf) +{ + if (!(zfs_flags & ZFS_DEBUG_MODIFY)) + return; + + if (ARC_BUF_COMPRESSED(buf)) + return; + + ASSERT(HDR_HAS_L1HDR(buf->b_hdr)); + arc_cksum_compute(buf); +} + +/* + * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, + * the following functions should be used to ensure that the flags are + * updated in a thread-safe way. When manipulating the flags either + * the hash_lock must be held or the hdr must be undiscoverable. This + * ensures that we're not racing with any other threads when updating + * the flags. + */ +static inline void +arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) +{ + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + hdr->b_flags |= flags; +} + +static inline void +arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) +{ + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + hdr->b_flags &= ~flags; +} + +/* + * Setting the compression bits in the arc_buf_hdr_t's b_flags is + * done in a special way since we have to clear and set bits + * at the same time. Consumers that wish to set the compression bits + * must use this function to ensure that the flags are updated in + * thread-safe manner. + */ +static void +arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) +{ + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + + /* + * Holes and embedded blocks will always have a psize = 0 so + * we ignore the compression of the blkptr and set the + * want to uncompress them. Mark them as uncompressed. + */ + if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { + arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); + ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); + } else { + arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); + ASSERT(HDR_COMPRESSION_ENABLED(hdr)); + } + + HDR_SET_COMPRESS(hdr, cmp); + ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); +} + +/* + * Looks for another buf on the same hdr which has the data decompressed, copies + * from it, and returns true. If no such buf exists, returns false. + */ +static boolean_t +arc_buf_try_copy_decompressed_data(arc_buf_t *buf) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + boolean_t copied = B_FALSE; + + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT3P(buf->b_data, !=, NULL); + ASSERT(!ARC_BUF_COMPRESSED(buf)); + + for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL; + from = from->b_next) { + /* can't use our own data buffer */ + if (from == buf) { + continue; + } + + if (!ARC_BUF_COMPRESSED(from)) { + bcopy(from->b_data, buf->b_data, arc_buf_size(buf)); + copied = B_TRUE; + break; + } + } + + /* + * There were no decompressed bufs, so there should not be a + * checksum on the hdr either. + */ + if (zfs_flags & ZFS_DEBUG_MODIFY) + EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL); + + return (copied); +} + +/* + * Allocates an ARC buf header that's in an evicted & L2-cached state. + * This is used during l2arc reconstruction to make empty ARC buffers + * which circumvent the regular disk->arc->l2arc path and instead come + * into being in the reverse order, i.e. l2arc->arc. + */ +static arc_buf_hdr_t * +arc_buf_alloc_l2only(size_t size, arc_buf_contents_t type, l2arc_dev_t *dev, + dva_t dva, uint64_t daddr, int32_t psize, uint64_t birth, + enum zio_compress compress, uint8_t complevel, boolean_t protected, + boolean_t prefetch) +{ + arc_buf_hdr_t *hdr; + + ASSERT(size != 0); + hdr = kmem_cache_alloc(hdr_l2only_cache, KM_SLEEP); + hdr->b_birth = birth; + hdr->b_type = type; + hdr->b_flags = 0; + arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L2HDR); + HDR_SET_LSIZE(hdr, size); + HDR_SET_PSIZE(hdr, psize); + arc_hdr_set_compress(hdr, compress); + hdr->b_complevel = complevel; + if (protected) + arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED); + if (prefetch) + arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); + hdr->b_spa = spa_load_guid(dev->l2ad_vdev->vdev_spa); + + hdr->b_dva = dva; + + hdr->b_l2hdr.b_dev = dev; + hdr->b_l2hdr.b_daddr = daddr; + + return (hdr); +} + +/* + * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t. + */ +static uint64_t +arc_hdr_size(arc_buf_hdr_t *hdr) +{ + uint64_t size; + + if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF && + HDR_GET_PSIZE(hdr) > 0) { + size = HDR_GET_PSIZE(hdr); + } else { + ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); + size = HDR_GET_LSIZE(hdr); + } + return (size); +} + +static int +arc_hdr_authenticate(arc_buf_hdr_t *hdr, spa_t *spa, uint64_t dsobj) +{ + int ret; + uint64_t csize; + uint64_t lsize = HDR_GET_LSIZE(hdr); + uint64_t psize = HDR_GET_PSIZE(hdr); + void *tmpbuf = NULL; + abd_t *abd = hdr->b_l1hdr.b_pabd; + + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + ASSERT(HDR_AUTHENTICATED(hdr)); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + + /* + * The MAC is calculated on the compressed data that is stored on disk. + * However, if compressed arc is disabled we will only have the + * decompressed data available to us now. Compress it into a temporary + * abd so we can verify the MAC. The performance overhead of this will + * be relatively low, since most objects in an encrypted objset will + * be encrypted (instead of authenticated) anyway. + */ + if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && + !HDR_COMPRESSION_ENABLED(hdr)) { + tmpbuf = zio_buf_alloc(lsize); + abd = abd_get_from_buf(tmpbuf, lsize); + abd_take_ownership_of_buf(abd, B_TRUE); + csize = zio_compress_data(HDR_GET_COMPRESS(hdr), + hdr->b_l1hdr.b_pabd, tmpbuf, lsize, hdr->b_complevel); + ASSERT3U(csize, <=, psize); + abd_zero_off(abd, csize, psize - csize); + } + + /* + * Authentication is best effort. We authenticate whenever the key is + * available. If we succeed we clear ARC_FLAG_NOAUTH. + */ + if (hdr->b_crypt_hdr.b_ot == DMU_OT_OBJSET) { + ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); + ASSERT3U(lsize, ==, psize); + ret = spa_do_crypt_objset_mac_abd(B_FALSE, spa, dsobj, abd, + psize, hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS); + } else { + ret = spa_do_crypt_mac_abd(B_FALSE, spa, dsobj, abd, psize, + hdr->b_crypt_hdr.b_mac); + } + + if (ret == 0) + arc_hdr_clear_flags(hdr, ARC_FLAG_NOAUTH); + else if (ret != ENOENT) + goto error; + + if (tmpbuf != NULL) + abd_free(abd); + + return (0); + +error: + if (tmpbuf != NULL) + abd_free(abd); + + return (ret); +} + +/* + * This function will take a header that only has raw encrypted data in + * b_crypt_hdr.b_rabd and decrypt it into a new buffer which is stored in + * b_l1hdr.b_pabd. If designated in the header flags, this function will + * also decompress the data. + */ +static int +arc_hdr_decrypt(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb) +{ + int ret; + abd_t *cabd = NULL; + void *tmp = NULL; + boolean_t no_crypt = B_FALSE; + boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS); + + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + ASSERT(HDR_ENCRYPTED(hdr)); + + arc_hdr_alloc_abd(hdr, ARC_HDR_DO_ADAPT); + + ret = spa_do_crypt_abd(B_FALSE, spa, zb, hdr->b_crypt_hdr.b_ot, + B_FALSE, bswap, hdr->b_crypt_hdr.b_salt, hdr->b_crypt_hdr.b_iv, + hdr->b_crypt_hdr.b_mac, HDR_GET_PSIZE(hdr), hdr->b_l1hdr.b_pabd, + hdr->b_crypt_hdr.b_rabd, &no_crypt); + if (ret != 0) + goto error; + + if (no_crypt) { + abd_copy(hdr->b_l1hdr.b_pabd, hdr->b_crypt_hdr.b_rabd, + HDR_GET_PSIZE(hdr)); + } + + /* + * If this header has disabled arc compression but the b_pabd is + * compressed after decrypting it, we need to decompress the newly + * decrypted data. + */ + if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && + !HDR_COMPRESSION_ENABLED(hdr)) { + /* + * We want to make sure that we are correctly honoring the + * zfs_abd_scatter_enabled setting, so we allocate an abd here + * and then loan a buffer from it, rather than allocating a + * linear buffer and wrapping it in an abd later. + */ + cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr, B_TRUE); + tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr)); + + ret = zio_decompress_data(HDR_GET_COMPRESS(hdr), + hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr), + HDR_GET_LSIZE(hdr), &hdr->b_complevel); + if (ret != 0) { + abd_return_buf(cabd, tmp, arc_hdr_size(hdr)); + goto error; + } + + abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr)); + arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, + arc_hdr_size(hdr), hdr); + hdr->b_l1hdr.b_pabd = cabd; + } + + return (0); + +error: + arc_hdr_free_abd(hdr, B_FALSE); + if (cabd != NULL) + arc_free_data_buf(hdr, cabd, arc_hdr_size(hdr), hdr); + + return (ret); +} + +/* + * This function is called during arc_buf_fill() to prepare the header's + * abd plaintext pointer for use. This involves authenticated protected + * data and decrypting encrypted data into the plaintext abd. + */ +static int +arc_fill_hdr_crypt(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, spa_t *spa, + const zbookmark_phys_t *zb, boolean_t noauth) +{ + int ret; + + ASSERT(HDR_PROTECTED(hdr)); + + if (hash_lock != NULL) + mutex_enter(hash_lock); + + if (HDR_NOAUTH(hdr) && !noauth) { + /* + * The caller requested authenticated data but our data has + * not been authenticated yet. Verify the MAC now if we can. + */ + ret = arc_hdr_authenticate(hdr, spa, zb->zb_objset); + if (ret != 0) + goto error; + } else if (HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd == NULL) { + /* + * If we only have the encrypted version of the data, but the + * unencrypted version was requested we take this opportunity + * to store the decrypted version in the header for future use. + */ + ret = arc_hdr_decrypt(hdr, spa, zb); + if (ret != 0) + goto error; + } + + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + + if (hash_lock != NULL) + mutex_exit(hash_lock); + + return (0); + +error: + if (hash_lock != NULL) + mutex_exit(hash_lock); + + return (ret); +} + +/* + * This function is used by the dbuf code to decrypt bonus buffers in place. + * The dbuf code itself doesn't have any locking for decrypting a shared dnode + * block, so we use the hash lock here to protect against concurrent calls to + * arc_buf_fill(). + */ +static void +arc_buf_untransform_in_place(arc_buf_t *buf, kmutex_t *hash_lock) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + ASSERT(HDR_ENCRYPTED(hdr)); + ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE); + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + + zio_crypt_copy_dnode_bonus(hdr->b_l1hdr.b_pabd, buf->b_data, + arc_buf_size(buf)); + buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED; + buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; + hdr->b_crypt_hdr.b_ebufcnt -= 1; +} + +/* + * Given a buf that has a data buffer attached to it, this function will + * efficiently fill the buf with data of the specified compression setting from + * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr + * are already sharing a data buf, no copy is performed. + * + * If the buf is marked as compressed but uncompressed data was requested, this + * will allocate a new data buffer for the buf, remove that flag, and fill the + * buf with uncompressed data. You can't request a compressed buf on a hdr with + * uncompressed data, and (since we haven't added support for it yet) if you + * want compressed data your buf must already be marked as compressed and have + * the correct-sized data buffer. + */ +static int +arc_buf_fill(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb, + arc_fill_flags_t flags) +{ + int error = 0; + arc_buf_hdr_t *hdr = buf->b_hdr; + boolean_t hdr_compressed = + (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF); + boolean_t compressed = (flags & ARC_FILL_COMPRESSED) != 0; + boolean_t encrypted = (flags & ARC_FILL_ENCRYPTED) != 0; + dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; + kmutex_t *hash_lock = (flags & ARC_FILL_LOCKED) ? NULL : HDR_LOCK(hdr); + + ASSERT3P(buf->b_data, !=, NULL); + IMPLY(compressed, hdr_compressed || ARC_BUF_ENCRYPTED(buf)); + IMPLY(compressed, ARC_BUF_COMPRESSED(buf)); + IMPLY(encrypted, HDR_ENCRYPTED(hdr)); + IMPLY(encrypted, ARC_BUF_ENCRYPTED(buf)); + IMPLY(encrypted, ARC_BUF_COMPRESSED(buf)); + IMPLY(encrypted, !ARC_BUF_SHARED(buf)); + + /* + * If the caller wanted encrypted data we just need to copy it from + * b_rabd and potentially byteswap it. We won't be able to do any + * further transforms on it. + */ + if (encrypted) { + ASSERT(HDR_HAS_RABD(hdr)); + abd_copy_to_buf(buf->b_data, hdr->b_crypt_hdr.b_rabd, + HDR_GET_PSIZE(hdr)); + goto byteswap; + } + + /* + * Adjust encrypted and authenticated headers to accommodate + * the request if needed. Dnode blocks (ARC_FILL_IN_PLACE) are + * allowed to fail decryption due to keys not being loaded + * without being marked as an IO error. + */ + if (HDR_PROTECTED(hdr)) { + error = arc_fill_hdr_crypt(hdr, hash_lock, spa, + zb, !!(flags & ARC_FILL_NOAUTH)); + if (error == EACCES && (flags & ARC_FILL_IN_PLACE) != 0) { + return (error); + } else if (error != 0) { + if (hash_lock != NULL) + mutex_enter(hash_lock); + arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); + if (hash_lock != NULL) + mutex_exit(hash_lock); + return (error); + } + } + + /* + * There is a special case here for dnode blocks which are + * decrypting their bonus buffers. These blocks may request to + * be decrypted in-place. This is necessary because there may + * be many dnodes pointing into this buffer and there is + * currently no method to synchronize replacing the backing + * b_data buffer and updating all of the pointers. Here we use + * the hash lock to ensure there are no races. If the need + * arises for other types to be decrypted in-place, they must + * add handling here as well. + */ + if ((flags & ARC_FILL_IN_PLACE) != 0) { + ASSERT(!hdr_compressed); + ASSERT(!compressed); + ASSERT(!encrypted); + + if (HDR_ENCRYPTED(hdr) && ARC_BUF_ENCRYPTED(buf)) { + ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE); + + if (hash_lock != NULL) + mutex_enter(hash_lock); + arc_buf_untransform_in_place(buf, hash_lock); + if (hash_lock != NULL) + mutex_exit(hash_lock); + + /* Compute the hdr's checksum if necessary */ + arc_cksum_compute(buf); + } + + return (0); + } + + if (hdr_compressed == compressed) { + if (!arc_buf_is_shared(buf)) { + abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd, + arc_buf_size(buf)); + } + } else { + ASSERT(hdr_compressed); + ASSERT(!compressed); + ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); + + /* + * If the buf is sharing its data with the hdr, unlink it and + * allocate a new data buffer for the buf. + */ + if (arc_buf_is_shared(buf)) { + ASSERT(ARC_BUF_COMPRESSED(buf)); + + /* We need to give the buf its own b_data */ + buf->b_flags &= ~ARC_BUF_FLAG_SHARED; + buf->b_data = + arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); + arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); + + /* Previously overhead was 0; just add new overhead */ + ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); + } else if (ARC_BUF_COMPRESSED(buf)) { + /* We need to reallocate the buf's b_data */ + arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr), + buf); + buf->b_data = + arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); + + /* We increased the size of b_data; update overhead */ + ARCSTAT_INCR(arcstat_overhead_size, + HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr)); + } + + /* + * Regardless of the buf's previous compression settings, it + * should not be compressed at the end of this function. + */ + buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; + + /* + * Try copying the data from another buf which already has a + * decompressed version. If that's not possible, it's time to + * bite the bullet and decompress the data from the hdr. + */ + if (arc_buf_try_copy_decompressed_data(buf)) { + /* Skip byteswapping and checksumming (already done) */ + return (0); + } else { + error = zio_decompress_data(HDR_GET_COMPRESS(hdr), + hdr->b_l1hdr.b_pabd, buf->b_data, + HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr), + &hdr->b_complevel); + + /* + * Absent hardware errors or software bugs, this should + * be impossible, but log it anyway so we can debug it. + */ + if (error != 0) { + zfs_dbgmsg( + "hdr %px, compress %d, psize %d, lsize %d", + hdr, arc_hdr_get_compress(hdr), + HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); + if (hash_lock != NULL) + mutex_enter(hash_lock); + arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); + if (hash_lock != NULL) + mutex_exit(hash_lock); + return (SET_ERROR(EIO)); + } + } + } + +byteswap: + /* Byteswap the buf's data if necessary */ + if (bswap != DMU_BSWAP_NUMFUNCS) { + ASSERT(!HDR_SHARED_DATA(hdr)); + ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); + dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); + } + + /* Compute the hdr's checksum if necessary */ + arc_cksum_compute(buf); + + return (0); +} + +/* + * If this function is being called to decrypt an encrypted buffer or verify an + * authenticated one, the key must be loaded and a mapping must be made + * available in the keystore via spa_keystore_create_mapping() or one of its + * callers. + */ +int +arc_untransform(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb, + boolean_t in_place) +{ + int ret; + arc_fill_flags_t flags = 0; + + if (in_place) + flags |= ARC_FILL_IN_PLACE; + + ret = arc_buf_fill(buf, spa, zb, flags); + if (ret == ECKSUM) { + /* + * Convert authentication and decryption errors to EIO + * (and generate an ereport) before leaving the ARC. + */ + ret = SET_ERROR(EIO); + spa_log_error(spa, zb); + zfs_ereport_post(FM_EREPORT_ZFS_AUTHENTICATION, + spa, NULL, zb, NULL, 0, 0); + } + + return (ret); +} + +/* + * Increment the amount of evictable space in the arc_state_t's refcount. + * We account for the space used by the hdr and the arc buf individually + * so that we can add and remove them from the refcount individually. + */ +static void +arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) +{ + arc_buf_contents_t type = arc_buf_type(hdr); + + ASSERT(HDR_HAS_L1HDR(hdr)); + + if (GHOST_STATE(state)) { + ASSERT0(hdr->b_l1hdr.b_bufcnt); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + (void) zfs_refcount_add_many(&state->arcs_esize[type], + HDR_GET_LSIZE(hdr), hdr); + return; + } + + ASSERT(!GHOST_STATE(state)); + if (hdr->b_l1hdr.b_pabd != NULL) { + (void) zfs_refcount_add_many(&state->arcs_esize[type], + arc_hdr_size(hdr), hdr); + } + if (HDR_HAS_RABD(hdr)) { + (void) zfs_refcount_add_many(&state->arcs_esize[type], + HDR_GET_PSIZE(hdr), hdr); + } + + for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; + buf = buf->b_next) { + if (arc_buf_is_shared(buf)) + continue; + (void) zfs_refcount_add_many(&state->arcs_esize[type], + arc_buf_size(buf), buf); + } +} + +/* + * Decrement the amount of evictable space in the arc_state_t's refcount. + * We account for the space used by the hdr and the arc buf individually + * so that we can add and remove them from the refcount individually. + */ +static void +arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) +{ + arc_buf_contents_t type = arc_buf_type(hdr); + + ASSERT(HDR_HAS_L1HDR(hdr)); + + if (GHOST_STATE(state)) { + ASSERT0(hdr->b_l1hdr.b_bufcnt); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + (void) zfs_refcount_remove_many(&state->arcs_esize[type], + HDR_GET_LSIZE(hdr), hdr); + return; + } + + ASSERT(!GHOST_STATE(state)); + if (hdr->b_l1hdr.b_pabd != NULL) { + (void) zfs_refcount_remove_many(&state->arcs_esize[type], + arc_hdr_size(hdr), hdr); + } + if (HDR_HAS_RABD(hdr)) { + (void) zfs_refcount_remove_many(&state->arcs_esize[type], + HDR_GET_PSIZE(hdr), hdr); + } + + for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; + buf = buf->b_next) { + if (arc_buf_is_shared(buf)) + continue; + (void) zfs_refcount_remove_many(&state->arcs_esize[type], + arc_buf_size(buf), buf); + } +} + +/* + * Add a reference to this hdr indicating that someone is actively + * referencing that memory. When the refcount transitions from 0 to 1, + * we remove it from the respective arc_state_t list to indicate that + * it is not evictable. + */ +static void +add_reference(arc_buf_hdr_t *hdr, void *tag) +{ + arc_state_t *state; + + ASSERT(HDR_HAS_L1HDR(hdr)); + if (!HDR_EMPTY(hdr) && !MUTEX_HELD(HDR_LOCK(hdr))) { + ASSERT(hdr->b_l1hdr.b_state == arc_anon); + ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + } + + state = hdr->b_l1hdr.b_state; + + if ((zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && + (state != arc_anon)) { + /* We don't use the L2-only state list. */ + if (state != arc_l2c_only) { + multilist_remove(state->arcs_list[arc_buf_type(hdr)], + hdr); + arc_evictable_space_decrement(hdr, state); + } + /* remove the prefetch flag if we get a reference */ + arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); + } +} + +/* + * Remove a reference from this hdr. When the reference transitions from + * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's + * list making it eligible for eviction. + */ +static int +remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) +{ + int cnt; + arc_state_t *state = hdr->b_l1hdr.b_state; + + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); + ASSERT(!GHOST_STATE(state)); + + /* + * arc_l2c_only counts as a ghost state so we don't need to explicitly + * check to prevent usage of the arc_l2c_only list. + */ + if (((cnt = zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && + (state != arc_anon)) { + multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr); + ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); + arc_evictable_space_increment(hdr, state); + } + return (cnt); +} + +/* + * Returns detailed information about a specific arc buffer. When the + * state_index argument is set the function will calculate the arc header + * list position for its arc state. Since this requires a linear traversal + * callers are strongly encourage not to do this. However, it can be helpful + * for targeted analysis so the functionality is provided. + */ +void +arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index) +{ + arc_buf_hdr_t *hdr = ab->b_hdr; + l1arc_buf_hdr_t *l1hdr = NULL; + l2arc_buf_hdr_t *l2hdr = NULL; + arc_state_t *state = NULL; + + memset(abi, 0, sizeof (arc_buf_info_t)); + + if (hdr == NULL) + return; + + abi->abi_flags = hdr->b_flags; + + if (HDR_HAS_L1HDR(hdr)) { + l1hdr = &hdr->b_l1hdr; + state = l1hdr->b_state; + } + if (HDR_HAS_L2HDR(hdr)) + l2hdr = &hdr->b_l2hdr; + + if (l1hdr) { + abi->abi_bufcnt = l1hdr->b_bufcnt; + abi->abi_access = l1hdr->b_arc_access; + abi->abi_mru_hits = l1hdr->b_mru_hits; + abi->abi_mru_ghost_hits = l1hdr->b_mru_ghost_hits; + abi->abi_mfu_hits = l1hdr->b_mfu_hits; + abi->abi_mfu_ghost_hits = l1hdr->b_mfu_ghost_hits; + abi->abi_holds = zfs_refcount_count(&l1hdr->b_refcnt); + } + + if (l2hdr) { + abi->abi_l2arc_dattr = l2hdr->b_daddr; + abi->abi_l2arc_hits = l2hdr->b_hits; + } + + abi->abi_state_type = state ? state->arcs_state : ARC_STATE_ANON; + abi->abi_state_contents = arc_buf_type(hdr); + abi->abi_size = arc_hdr_size(hdr); +} + +/* + * Move the supplied buffer to the indicated state. The hash lock + * for the buffer must be held by the caller. + */ +static void +arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, + kmutex_t *hash_lock) +{ + arc_state_t *old_state; + int64_t refcnt; + uint32_t bufcnt; + boolean_t update_old, update_new; + arc_buf_contents_t buftype = arc_buf_type(hdr); + + /* + * We almost always have an L1 hdr here, since we call arc_hdr_realloc() + * in arc_read() when bringing a buffer out of the L2ARC. However, the + * L1 hdr doesn't always exist when we change state to arc_anon before + * destroying a header, in which case reallocating to add the L1 hdr is + * pointless. + */ + if (HDR_HAS_L1HDR(hdr)) { + old_state = hdr->b_l1hdr.b_state; + refcnt = zfs_refcount_count(&hdr->b_l1hdr.b_refcnt); + bufcnt = hdr->b_l1hdr.b_bufcnt; + update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL || + HDR_HAS_RABD(hdr)); + } else { + old_state = arc_l2c_only; + refcnt = 0; + bufcnt = 0; + update_old = B_FALSE; + } + update_new = update_old; + + ASSERT(MUTEX_HELD(hash_lock)); + ASSERT3P(new_state, !=, old_state); + ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); + ASSERT(old_state != arc_anon || bufcnt <= 1); + + /* + * If this buffer is evictable, transfer it from the + * old state list to the new state list. + */ + if (refcnt == 0) { + if (old_state != arc_anon && old_state != arc_l2c_only) { + ASSERT(HDR_HAS_L1HDR(hdr)); + multilist_remove(old_state->arcs_list[buftype], hdr); + + if (GHOST_STATE(old_state)) { + ASSERT0(bufcnt); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + update_old = B_TRUE; + } + arc_evictable_space_decrement(hdr, old_state); + } + if (new_state != arc_anon && new_state != arc_l2c_only) { + /* + * An L1 header always exists here, since if we're + * moving to some L1-cached state (i.e. not l2c_only or + * anonymous), we realloc the header to add an L1hdr + * beforehand. + */ + ASSERT(HDR_HAS_L1HDR(hdr)); + multilist_insert(new_state->arcs_list[buftype], hdr); + + if (GHOST_STATE(new_state)) { + ASSERT0(bufcnt); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + update_new = B_TRUE; + } + arc_evictable_space_increment(hdr, new_state); + } + } + + ASSERT(!HDR_EMPTY(hdr)); + if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) + buf_hash_remove(hdr); + + /* adjust state sizes (ignore arc_l2c_only) */ + + if (update_new && new_state != arc_l2c_only) { + ASSERT(HDR_HAS_L1HDR(hdr)); + if (GHOST_STATE(new_state)) { + ASSERT0(bufcnt); + + /* + * When moving a header to a ghost state, we first + * remove all arc buffers. Thus, we'll have a + * bufcnt of zero, and no arc buffer to use for + * the reference. As a result, we use the arc + * header pointer for the reference. + */ + (void) zfs_refcount_add_many(&new_state->arcs_size, + HDR_GET_LSIZE(hdr), hdr); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + } else { + uint32_t buffers = 0; + + /* + * Each individual buffer holds a unique reference, + * thus we must remove each of these references one + * at a time. + */ + for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; + buf = buf->b_next) { + ASSERT3U(bufcnt, !=, 0); + buffers++; + + /* + * When the arc_buf_t is sharing the data + * block with the hdr, the owner of the + * reference belongs to the hdr. Only + * add to the refcount if the arc_buf_t is + * not shared. + */ + if (arc_buf_is_shared(buf)) + continue; + + (void) zfs_refcount_add_many( + &new_state->arcs_size, + arc_buf_size(buf), buf); + } + ASSERT3U(bufcnt, ==, buffers); + + if (hdr->b_l1hdr.b_pabd != NULL) { + (void) zfs_refcount_add_many( + &new_state->arcs_size, + arc_hdr_size(hdr), hdr); + } + + if (HDR_HAS_RABD(hdr)) { + (void) zfs_refcount_add_many( + &new_state->arcs_size, + HDR_GET_PSIZE(hdr), hdr); + } + } + } + + if (update_old && old_state != arc_l2c_only) { + ASSERT(HDR_HAS_L1HDR(hdr)); + if (GHOST_STATE(old_state)) { + ASSERT0(bufcnt); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + + /* + * When moving a header off of a ghost state, + * the header will not contain any arc buffers. + * We use the arc header pointer for the reference + * which is exactly what we did when we put the + * header on the ghost state. + */ + + (void) zfs_refcount_remove_many(&old_state->arcs_size, + HDR_GET_LSIZE(hdr), hdr); + } else { + uint32_t buffers = 0; + + /* + * Each individual buffer holds a unique reference, + * thus we must remove each of these references one + * at a time. + */ + for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; + buf = buf->b_next) { + ASSERT3U(bufcnt, !=, 0); + buffers++; + + /* + * When the arc_buf_t is sharing the data + * block with the hdr, the owner of the + * reference belongs to the hdr. Only + * add to the refcount if the arc_buf_t is + * not shared. + */ + if (arc_buf_is_shared(buf)) + continue; + + (void) zfs_refcount_remove_many( + &old_state->arcs_size, arc_buf_size(buf), + buf); + } + ASSERT3U(bufcnt, ==, buffers); + ASSERT(hdr->b_l1hdr.b_pabd != NULL || + HDR_HAS_RABD(hdr)); + + if (hdr->b_l1hdr.b_pabd != NULL) { + (void) zfs_refcount_remove_many( + &old_state->arcs_size, arc_hdr_size(hdr), + hdr); + } + + if (HDR_HAS_RABD(hdr)) { + (void) zfs_refcount_remove_many( + &old_state->arcs_size, HDR_GET_PSIZE(hdr), + hdr); + } + } + } + + if (HDR_HAS_L1HDR(hdr)) + hdr->b_l1hdr.b_state = new_state; + + /* + * L2 headers should never be on the L2 state list since they don't + * have L1 headers allocated. + */ + ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && + multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); +} + +void +arc_space_consume(uint64_t space, arc_space_type_t type) +{ + ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); + + switch (type) { + default: + break; + case ARC_SPACE_DATA: + aggsum_add(&astat_data_size, space); + break; + case ARC_SPACE_META: + aggsum_add(&astat_metadata_size, space); + break; + case ARC_SPACE_BONUS: + aggsum_add(&astat_bonus_size, space); + break; + case ARC_SPACE_DNODE: + aggsum_add(&astat_dnode_size, space); + break; + case ARC_SPACE_DBUF: + aggsum_add(&astat_dbuf_size, space); + break; + case ARC_SPACE_HDRS: + aggsum_add(&astat_hdr_size, space); + break; + case ARC_SPACE_L2HDRS: + aggsum_add(&astat_l2_hdr_size, space); + break; + case ARC_SPACE_ABD_CHUNK_WASTE: + /* + * Note: this includes space wasted by all scatter ABD's, not + * just those allocated by the ARC. But the vast majority of + * scatter ABD's come from the ARC, because other users are + * very short-lived. + */ + aggsum_add(&astat_abd_chunk_waste_size, space); + break; + } + + if (type != ARC_SPACE_DATA && type != ARC_SPACE_ABD_CHUNK_WASTE) + aggsum_add(&arc_meta_used, space); + + aggsum_add(&arc_size, space); +} + +void +arc_space_return(uint64_t space, arc_space_type_t type) +{ + ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); + + switch (type) { + default: + break; + case ARC_SPACE_DATA: + aggsum_add(&astat_data_size, -space); + break; + case ARC_SPACE_META: + aggsum_add(&astat_metadata_size, -space); + break; + case ARC_SPACE_BONUS: + aggsum_add(&astat_bonus_size, -space); + break; + case ARC_SPACE_DNODE: + aggsum_add(&astat_dnode_size, -space); + break; + case ARC_SPACE_DBUF: + aggsum_add(&astat_dbuf_size, -space); + break; + case ARC_SPACE_HDRS: + aggsum_add(&astat_hdr_size, -space); + break; + case ARC_SPACE_L2HDRS: + aggsum_add(&astat_l2_hdr_size, -space); + break; + case ARC_SPACE_ABD_CHUNK_WASTE: + aggsum_add(&astat_abd_chunk_waste_size, -space); + break; + } + + if (type != ARC_SPACE_DATA && type != ARC_SPACE_ABD_CHUNK_WASTE) { + ASSERT(aggsum_compare(&arc_meta_used, space) >= 0); + /* + * We use the upper bound here rather than the precise value + * because the arc_meta_max value doesn't need to be + * precise. It's only consumed by humans via arcstats. + */ + if (arc_meta_max < aggsum_upper_bound(&arc_meta_used)) + arc_meta_max = aggsum_upper_bound(&arc_meta_used); + aggsum_add(&arc_meta_used, -space); + } + + ASSERT(aggsum_compare(&arc_size, space) >= 0); + aggsum_add(&arc_size, -space); +} + +/* + * Given a hdr and a buf, returns whether that buf can share its b_data buffer + * with the hdr's b_pabd. + */ +static boolean_t +arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf) +{ + /* + * The criteria for sharing a hdr's data are: + * 1. the buffer is not encrypted + * 2. the hdr's compression matches the buf's compression + * 3. the hdr doesn't need to be byteswapped + * 4. the hdr isn't already being shared + * 5. the buf is either compressed or it is the last buf in the hdr list + * + * Criterion #5 maintains the invariant that shared uncompressed + * bufs must be the final buf in the hdr's b_buf list. Reading this, you + * might ask, "if a compressed buf is allocated first, won't that be the + * last thing in the list?", but in that case it's impossible to create + * a shared uncompressed buf anyway (because the hdr must be compressed + * to have the compressed buf). You might also think that #3 is + * sufficient to make this guarantee, however it's possible + * (specifically in the rare L2ARC write race mentioned in + * arc_buf_alloc_impl()) there will be an existing uncompressed buf that + * is shareable, but wasn't at the time of its allocation. Rather than + * allow a new shared uncompressed buf to be created and then shuffle + * the list around to make it the last element, this simply disallows + * sharing if the new buf isn't the first to be added. + */ + ASSERT3P(buf->b_hdr, ==, hdr); + boolean_t hdr_compressed = + arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF; + boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0; + return (!ARC_BUF_ENCRYPTED(buf) && + buf_compressed == hdr_compressed && + hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && + !HDR_SHARED_DATA(hdr) && + (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf))); +} + +/* + * Allocate a buf for this hdr. If you care about the data that's in the hdr, + * or if you want a compressed buffer, pass those flags in. Returns 0 if the + * copy was made successfully, or an error code otherwise. + */ +static int +arc_buf_alloc_impl(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb, + void *tag, boolean_t encrypted, boolean_t compressed, boolean_t noauth, + boolean_t fill, arc_buf_t **ret) +{ + arc_buf_t *buf; + arc_fill_flags_t flags = ARC_FILL_LOCKED; + + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); + VERIFY(hdr->b_type == ARC_BUFC_DATA || + hdr->b_type == ARC_BUFC_METADATA); + ASSERT3P(ret, !=, NULL); + ASSERT3P(*ret, ==, NULL); + IMPLY(encrypted, compressed); + + hdr->b_l1hdr.b_mru_hits = 0; + hdr->b_l1hdr.b_mru_ghost_hits = 0; + hdr->b_l1hdr.b_mfu_hits = 0; + hdr->b_l1hdr.b_mfu_ghost_hits = 0; + hdr->b_l1hdr.b_l2_hits = 0; + + buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); + buf->b_hdr = hdr; + buf->b_data = NULL; + buf->b_next = hdr->b_l1hdr.b_buf; + buf->b_flags = 0; + + add_reference(hdr, tag); + + /* + * We're about to change the hdr's b_flags. We must either + * hold the hash_lock or be undiscoverable. + */ + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + + /* + * Only honor requests for compressed bufs if the hdr is actually + * compressed. This must be overridden if the buffer is encrypted since + * encrypted buffers cannot be decompressed. + */ + if (encrypted) { + buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; + buf->b_flags |= ARC_BUF_FLAG_ENCRYPTED; + flags |= ARC_FILL_COMPRESSED | ARC_FILL_ENCRYPTED; + } else if (compressed && + arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) { + buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; + flags |= ARC_FILL_COMPRESSED; + } + + if (noauth) { + ASSERT0(encrypted); + flags |= ARC_FILL_NOAUTH; + } + + /* + * If the hdr's data can be shared then we share the data buffer and + * set the appropriate bit in the hdr's b_flags to indicate the hdr is + * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new + * buffer to store the buf's data. + * + * There are two additional restrictions here because we're sharing + * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be + * actively involved in an L2ARC write, because if this buf is used by + * an arc_write() then the hdr's data buffer will be released when the + * write completes, even though the L2ARC write might still be using it. + * Second, the hdr's ABD must be linear so that the buf's user doesn't + * need to be ABD-aware. It must be allocated via + * zio_[data_]buf_alloc(), not as a page, because we need to be able + * to abd_release_ownership_of_buf(), which isn't allowed on "linear + * page" buffers because the ABD code needs to handle freeing them + * specially. + */ + boolean_t can_share = arc_can_share(hdr, buf) && + !HDR_L2_WRITING(hdr) && + hdr->b_l1hdr.b_pabd != NULL && + abd_is_linear(hdr->b_l1hdr.b_pabd) && + !abd_is_linear_page(hdr->b_l1hdr.b_pabd); + + /* Set up b_data and sharing */ + if (can_share) { + buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd); + buf->b_flags |= ARC_BUF_FLAG_SHARED; + arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); + } else { + buf->b_data = + arc_get_data_buf(hdr, arc_buf_size(buf), buf); + ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); + } + VERIFY3P(buf->b_data, !=, NULL); + + hdr->b_l1hdr.b_buf = buf; + hdr->b_l1hdr.b_bufcnt += 1; + if (encrypted) + hdr->b_crypt_hdr.b_ebufcnt += 1; + + /* + * If the user wants the data from the hdr, we need to either copy or + * decompress the data. + */ + if (fill) { + ASSERT3P(zb, !=, NULL); + return (arc_buf_fill(buf, spa, zb, flags)); + } + + return (0); +} + +static char *arc_onloan_tag = "onloan"; + +static inline void +arc_loaned_bytes_update(int64_t delta) +{ + atomic_add_64(&arc_loaned_bytes, delta); + + /* assert that it did not wrap around */ + ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); +} + +/* + * Loan out an anonymous arc buffer. Loaned buffers are not counted as in + * flight data by arc_tempreserve_space() until they are "returned". Loaned + * buffers must be returned to the arc before they can be used by the DMU or + * freed. + */ +arc_buf_t * +arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size) +{ + arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag, + is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size); + + arc_loaned_bytes_update(arc_buf_size(buf)); + + return (buf); +} + +arc_buf_t * +arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize, + enum zio_compress compression_type, uint8_t complevel) +{ + arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag, + psize, lsize, compression_type, complevel); + + arc_loaned_bytes_update(arc_buf_size(buf)); + + return (buf); +} + +arc_buf_t * +arc_loan_raw_buf(spa_t *spa, uint64_t dsobj, boolean_t byteorder, + const uint8_t *salt, const uint8_t *iv, const uint8_t *mac, + dmu_object_type_t ot, uint64_t psize, uint64_t lsize, + enum zio_compress compression_type, uint8_t complevel) +{ + arc_buf_t *buf = arc_alloc_raw_buf(spa, arc_onloan_tag, dsobj, + byteorder, salt, iv, mac, ot, psize, lsize, compression_type, + complevel); + + atomic_add_64(&arc_loaned_bytes, psize); + return (buf); +} + + +/* + * Return a loaned arc buffer to the arc. + */ +void +arc_return_buf(arc_buf_t *buf, void *tag) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + ASSERT3P(buf->b_data, !=, NULL); + ASSERT(HDR_HAS_L1HDR(hdr)); + (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag); + (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); + + arc_loaned_bytes_update(-arc_buf_size(buf)); +} + +/* Detach an arc_buf from a dbuf (tag) */ +void +arc_loan_inuse_buf(arc_buf_t *buf, void *tag) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + ASSERT3P(buf->b_data, !=, NULL); + ASSERT(HDR_HAS_L1HDR(hdr)); + (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); + (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); + + arc_loaned_bytes_update(arc_buf_size(buf)); +} + +static void +l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type) +{ + l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); + + df->l2df_abd = abd; + df->l2df_size = size; + df->l2df_type = type; + mutex_enter(&l2arc_free_on_write_mtx); + list_insert_head(l2arc_free_on_write, df); + mutex_exit(&l2arc_free_on_write_mtx); +} + +static void +arc_hdr_free_on_write(arc_buf_hdr_t *hdr, boolean_t free_rdata) +{ + arc_state_t *state = hdr->b_l1hdr.b_state; + arc_buf_contents_t type = arc_buf_type(hdr); + uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr); + + /* protected by hash lock, if in the hash table */ + if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { + ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT(state != arc_anon && state != arc_l2c_only); + + (void) zfs_refcount_remove_many(&state->arcs_esize[type], + size, hdr); + } + (void) zfs_refcount_remove_many(&state->arcs_size, size, hdr); + if (type == ARC_BUFC_METADATA) { + arc_space_return(size, ARC_SPACE_META); + } else { + ASSERT(type == ARC_BUFC_DATA); + arc_space_return(size, ARC_SPACE_DATA); + } + + if (free_rdata) { + l2arc_free_abd_on_write(hdr->b_crypt_hdr.b_rabd, size, type); + } else { + l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type); + } +} + +/* + * Share the arc_buf_t's data with the hdr. Whenever we are sharing the + * data buffer, we transfer the refcount ownership to the hdr and update + * the appropriate kstats. + */ +static void +arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) +{ + ASSERT(arc_can_share(hdr, buf)); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!ARC_BUF_ENCRYPTED(buf)); + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + + /* + * Start sharing the data buffer. We transfer the + * refcount ownership to the hdr since it always owns + * the refcount whenever an arc_buf_t is shared. + */ + zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size, + arc_hdr_size(hdr), buf, hdr); + hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf)); + abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd, + HDR_ISTYPE_METADATA(hdr)); + arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); + buf->b_flags |= ARC_BUF_FLAG_SHARED; + + /* + * Since we've transferred ownership to the hdr we need + * to increment its compressed and uncompressed kstats and + * decrement the overhead size. + */ + ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); + ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); + ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf)); +} + +static void +arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) +{ + ASSERT(arc_buf_is_shared(buf)); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + + /* + * We are no longer sharing this buffer so we need + * to transfer its ownership to the rightful owner. + */ + zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size, + arc_hdr_size(hdr), hdr, buf); + arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); + abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd); + abd_put(hdr->b_l1hdr.b_pabd); + hdr->b_l1hdr.b_pabd = NULL; + buf->b_flags &= ~ARC_BUF_FLAG_SHARED; + + /* + * Since the buffer is no longer shared between + * the arc buf and the hdr, count it as overhead. + */ + ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); + ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); + ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); +} + +/* + * Remove an arc_buf_t from the hdr's buf list and return the last + * arc_buf_t on the list. If no buffers remain on the list then return + * NULL. + */ +static arc_buf_t * +arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf) +{ + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + + arc_buf_t **bufp = &hdr->b_l1hdr.b_buf; + arc_buf_t *lastbuf = NULL; + + /* + * Remove the buf from the hdr list and locate the last + * remaining buffer on the list. + */ + while (*bufp != NULL) { + if (*bufp == buf) + *bufp = buf->b_next; + + /* + * If we've removed a buffer in the middle of + * the list then update the lastbuf and update + * bufp. + */ + if (*bufp != NULL) { + lastbuf = *bufp; + bufp = &(*bufp)->b_next; + } + } + buf->b_next = NULL; + ASSERT3P(lastbuf, !=, buf); + IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL); + IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL); + IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf)); + + return (lastbuf); +} + +/* + * Free up buf->b_data and pull the arc_buf_t off of the arc_buf_hdr_t's + * list and free it. + */ +static void +arc_buf_destroy_impl(arc_buf_t *buf) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + /* + * Free up the data associated with the buf but only if we're not + * sharing this with the hdr. If we are sharing it with the hdr, the + * hdr is responsible for doing the free. + */ + if (buf->b_data != NULL) { + /* + * We're about to change the hdr's b_flags. We must either + * hold the hash_lock or be undiscoverable. + */ + ASSERT(HDR_EMPTY_OR_LOCKED(hdr)); + + arc_cksum_verify(buf); + arc_buf_unwatch(buf); + + if (arc_buf_is_shared(buf)) { + arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); + } else { + uint64_t size = arc_buf_size(buf); + arc_free_data_buf(hdr, buf->b_data, size, buf); + ARCSTAT_INCR(arcstat_overhead_size, -size); + } + buf->b_data = NULL; + + ASSERT(hdr->b_l1hdr.b_bufcnt > 0); + hdr->b_l1hdr.b_bufcnt -= 1; + + if (ARC_BUF_ENCRYPTED(buf)) { + hdr->b_crypt_hdr.b_ebufcnt -= 1; + + /* + * If we have no more encrypted buffers and we've + * already gotten a copy of the decrypted data we can + * free b_rabd to save some space. + */ + if (hdr->b_crypt_hdr.b_ebufcnt == 0 && + HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd != NULL && + !HDR_IO_IN_PROGRESS(hdr)) { + arc_hdr_free_abd(hdr, B_TRUE); + } + } + } + + arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); + + if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) { + /* + * If the current arc_buf_t is sharing its data buffer with the + * hdr, then reassign the hdr's b_pabd to share it with the new + * buffer at the end of the list. The shared buffer is always + * the last one on the hdr's buffer list. + * + * There is an equivalent case for compressed bufs, but since + * they aren't guaranteed to be the last buf in the list and + * that is an exceedingly rare case, we just allow that space be + * wasted temporarily. We must also be careful not to share + * encrypted buffers, since they cannot be shared. + */ + if (lastbuf != NULL && !ARC_BUF_ENCRYPTED(lastbuf)) { + /* Only one buf can be shared at once */ + VERIFY(!arc_buf_is_shared(lastbuf)); + /* hdr is uncompressed so can't have compressed buf */ + VERIFY(!ARC_BUF_COMPRESSED(lastbuf)); + + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + arc_hdr_free_abd(hdr, B_FALSE); + + /* + * We must setup a new shared block between the + * last buffer and the hdr. The data would have + * been allocated by the arc buf so we need to transfer + * ownership to the hdr since it's now being shared. + */ + arc_share_buf(hdr, lastbuf); + } + } else if (HDR_SHARED_DATA(hdr)) { + /* + * Uncompressed shared buffers are always at the end + * of the list. Compressed buffers don't have the + * same requirements. This makes it hard to + * simply assert that the lastbuf is shared so + * we rely on the hdr's compression flags to determine + * if we have a compressed, shared buffer. + */ + ASSERT3P(lastbuf, !=, NULL); + ASSERT(arc_buf_is_shared(lastbuf) || + arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF); + } + + /* + * Free the checksum if we're removing the last uncompressed buf from + * this hdr. + */ + if (!arc_hdr_has_uncompressed_buf(hdr)) { + arc_cksum_free(hdr); + } + + /* clean up the buf */ + buf->b_hdr = NULL; + kmem_cache_free(buf_cache, buf); +} + +static void +arc_hdr_alloc_abd(arc_buf_hdr_t *hdr, int alloc_flags) +{ + uint64_t size; + boolean_t alloc_rdata = ((alloc_flags & ARC_HDR_ALLOC_RDATA) != 0); + boolean_t do_adapt = ((alloc_flags & ARC_HDR_DO_ADAPT) != 0); + + ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(!HDR_SHARED_DATA(hdr) || alloc_rdata); + IMPLY(alloc_rdata, HDR_PROTECTED(hdr)); + + if (alloc_rdata) { + size = HDR_GET_PSIZE(hdr); + ASSERT3P(hdr->b_crypt_hdr.b_rabd, ==, NULL); + hdr->b_crypt_hdr.b_rabd = arc_get_data_abd(hdr, size, hdr, + do_adapt); + ASSERT3P(hdr->b_crypt_hdr.b_rabd, !=, NULL); + ARCSTAT_INCR(arcstat_raw_size, size); + } else { + size = arc_hdr_size(hdr); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, size, hdr, + do_adapt); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + } + + ARCSTAT_INCR(arcstat_compressed_size, size); + ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); +} + +static void +arc_hdr_free_abd(arc_buf_hdr_t *hdr, boolean_t free_rdata) +{ + uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr); + + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr)); + IMPLY(free_rdata, HDR_HAS_RABD(hdr)); + + /* + * If the hdr is currently being written to the l2arc then + * we defer freeing the data by adding it to the l2arc_free_on_write + * list. The l2arc will free the data once it's finished + * writing it to the l2arc device. + */ + if (HDR_L2_WRITING(hdr)) { + arc_hdr_free_on_write(hdr, free_rdata); + ARCSTAT_BUMP(arcstat_l2_free_on_write); + } else if (free_rdata) { + arc_free_data_abd(hdr, hdr->b_crypt_hdr.b_rabd, size, hdr); + } else { + arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, size, hdr); + } + + if (free_rdata) { + hdr->b_crypt_hdr.b_rabd = NULL; + ARCSTAT_INCR(arcstat_raw_size, -size); + } else { + hdr->b_l1hdr.b_pabd = NULL; + } + + if (hdr->b_l1hdr.b_pabd == NULL && !HDR_HAS_RABD(hdr)) + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; + + ARCSTAT_INCR(arcstat_compressed_size, -size); + ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); +} + +static arc_buf_hdr_t * +arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, + boolean_t protected, enum zio_compress compression_type, uint8_t complevel, + arc_buf_contents_t type, boolean_t alloc_rdata) +{ + arc_buf_hdr_t *hdr; + int flags = ARC_HDR_DO_ADAPT; + + VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); + if (protected) { + hdr = kmem_cache_alloc(hdr_full_crypt_cache, KM_PUSHPAGE); + } else { + hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); + } + flags |= alloc_rdata ? ARC_HDR_ALLOC_RDATA : 0; + + ASSERT(HDR_EMPTY(hdr)); + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); + HDR_SET_PSIZE(hdr, psize); + HDR_SET_LSIZE(hdr, lsize); + hdr->b_spa = spa; + hdr->b_type = type; + hdr->b_flags = 0; + arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); + arc_hdr_set_compress(hdr, compression_type); + hdr->b_complevel = complevel; + if (protected) + arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED); + + hdr->b_l1hdr.b_state = arc_anon; + hdr->b_l1hdr.b_arc_access = 0; + hdr->b_l1hdr.b_bufcnt = 0; + hdr->b_l1hdr.b_buf = NULL; + + /* + * Allocate the hdr's buffer. This will contain either + * the compressed or uncompressed data depending on the block + * it references and compressed arc enablement. + */ + arc_hdr_alloc_abd(hdr, flags); + ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + + return (hdr); +} + +/* + * Transition between the two allocation states for the arc_buf_hdr struct. + * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without + * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller + * version is used when a cache buffer is only in the L2ARC in order to reduce + * memory usage. + */ +static arc_buf_hdr_t * +arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) +{ + ASSERT(HDR_HAS_L2HDR(hdr)); + + arc_buf_hdr_t *nhdr; + l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; + + ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || + (old == hdr_l2only_cache && new == hdr_full_cache)); + + /* + * if the caller wanted a new full header and the header is to be + * encrypted we will actually allocate the header from the full crypt + * cache instead. The same applies to freeing from the old cache. + */ + if (HDR_PROTECTED(hdr) && new == hdr_full_cache) + new = hdr_full_crypt_cache; + if (HDR_PROTECTED(hdr) && old == hdr_full_cache) + old = hdr_full_crypt_cache; + + nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); + + ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); + buf_hash_remove(hdr); + + bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); + + if (new == hdr_full_cache || new == hdr_full_crypt_cache) { + arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); + /* + * arc_access and arc_change_state need to be aware that a + * header has just come out of L2ARC, so we set its state to + * l2c_only even though it's about to change. + */ + nhdr->b_l1hdr.b_state = arc_l2c_only; + + /* Verify previous threads set to NULL before freeing */ + ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + } else { + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + ASSERT0(hdr->b_l1hdr.b_bufcnt); + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); + + /* + * If we've reached here, We must have been called from + * arc_evict_hdr(), as such we should have already been + * removed from any ghost list we were previously on + * (which protects us from racing with arc_evict_state), + * thus no locking is needed during this check. + */ + ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); + + /* + * A buffer must not be moved into the arc_l2c_only + * state if it's not finished being written out to the + * l2arc device. Otherwise, the b_l1hdr.b_pabd field + * might try to be accessed, even though it was removed. + */ + VERIFY(!HDR_L2_WRITING(hdr)); + VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + + arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); + } + /* + * The header has been reallocated so we need to re-insert it into any + * lists it was on. + */ + (void) buf_hash_insert(nhdr, NULL); + + ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); + + mutex_enter(&dev->l2ad_mtx); + + /* + * We must place the realloc'ed header back into the list at + * the same spot. Otherwise, if it's placed earlier in the list, + * l2arc_write_buffers() could find it during the function's + * write phase, and try to write it out to the l2arc. + */ + list_insert_after(&dev->l2ad_buflist, hdr, nhdr); + list_remove(&dev->l2ad_buflist, hdr); + + mutex_exit(&dev->l2ad_mtx); + + /* + * Since we're using the pointer address as the tag when + * incrementing and decrementing the l2ad_alloc refcount, we + * must remove the old pointer (that we're about to destroy) and + * add the new pointer to the refcount. Otherwise we'd remove + * the wrong pointer address when calling arc_hdr_destroy() later. + */ + + (void) zfs_refcount_remove_many(&dev->l2ad_alloc, + arc_hdr_size(hdr), hdr); + (void) zfs_refcount_add_many(&dev->l2ad_alloc, + arc_hdr_size(nhdr), nhdr); + + buf_discard_identity(hdr); + kmem_cache_free(old, hdr); + + return (nhdr); +} + +/* + * This function allows an L1 header to be reallocated as a crypt + * header and vice versa. If we are going to a crypt header, the + * new fields will be zeroed out. + */ +static arc_buf_hdr_t * +arc_hdr_realloc_crypt(arc_buf_hdr_t *hdr, boolean_t need_crypt) +{ + arc_buf_hdr_t *nhdr; + arc_buf_t *buf; + kmem_cache_t *ncache, *ocache; + unsigned nsize, osize; + + /* + * This function requires that hdr is in the arc_anon state. + * Therefore it won't have any L2ARC data for us to worry + * about copying. + */ + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(!HDR_HAS_L2HDR(hdr)); + ASSERT3U(!!HDR_PROTECTED(hdr), !=, need_crypt); + ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); + ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); + ASSERT(!list_link_active(&hdr->b_l2hdr.b_l2node)); + ASSERT3P(hdr->b_hash_next, ==, NULL); + + if (need_crypt) { + ncache = hdr_full_crypt_cache; + nsize = sizeof (hdr->b_crypt_hdr); + ocache = hdr_full_cache; + osize = HDR_FULL_SIZE; + } else { + ncache = hdr_full_cache; + nsize = HDR_FULL_SIZE; + ocache = hdr_full_crypt_cache; + osize = sizeof (hdr->b_crypt_hdr); + } + + nhdr = kmem_cache_alloc(ncache, KM_PUSHPAGE); + + /* + * Copy all members that aren't locks or condvars to the new header. + * No lists are pointing to us (as we asserted above), so we don't + * need to worry about the list nodes. + */ + nhdr->b_dva = hdr->b_dva; + nhdr->b_birth = hdr->b_birth; + nhdr->b_type = hdr->b_type; + nhdr->b_flags = hdr->b_flags; + nhdr->b_psize = hdr->b_psize; + nhdr->b_lsize = hdr->b_lsize; + nhdr->b_spa = hdr->b_spa; + nhdr->b_l1hdr.b_freeze_cksum = hdr->b_l1hdr.b_freeze_cksum; + nhdr->b_l1hdr.b_bufcnt = hdr->b_l1hdr.b_bufcnt; + nhdr->b_l1hdr.b_byteswap = hdr->b_l1hdr.b_byteswap; + nhdr->b_l1hdr.b_state = hdr->b_l1hdr.b_state; + nhdr->b_l1hdr.b_arc_access = hdr->b_l1hdr.b_arc_access; + nhdr->b_l1hdr.b_mru_hits = hdr->b_l1hdr.b_mru_hits; + nhdr->b_l1hdr.b_mru_ghost_hits = hdr->b_l1hdr.b_mru_ghost_hits; + nhdr->b_l1hdr.b_mfu_hits = hdr->b_l1hdr.b_mfu_hits; + nhdr->b_l1hdr.b_mfu_ghost_hits = hdr->b_l1hdr.b_mfu_ghost_hits; + nhdr->b_l1hdr.b_l2_hits = hdr->b_l1hdr.b_l2_hits; + nhdr->b_l1hdr.b_acb = hdr->b_l1hdr.b_acb; + nhdr->b_l1hdr.b_pabd = hdr->b_l1hdr.b_pabd; + + /* + * This zfs_refcount_add() exists only to ensure that the individual + * arc buffers always point to a header that is referenced, avoiding + * a small race condition that could trigger ASSERTs. + */ + (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, FTAG); + nhdr->b_l1hdr.b_buf = hdr->b_l1hdr.b_buf; + for (buf = nhdr->b_l1hdr.b_buf; buf != NULL; buf = buf->b_next) { + mutex_enter(&buf->b_evict_lock); + buf->b_hdr = nhdr; + mutex_exit(&buf->b_evict_lock); + } + + zfs_refcount_transfer(&nhdr->b_l1hdr.b_refcnt, &hdr->b_l1hdr.b_refcnt); + (void) zfs_refcount_remove(&nhdr->b_l1hdr.b_refcnt, FTAG); + ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt)); + + if (need_crypt) { + arc_hdr_set_flags(nhdr, ARC_FLAG_PROTECTED); + } else { + arc_hdr_clear_flags(nhdr, ARC_FLAG_PROTECTED); + } + + /* unset all members of the original hdr */ + bzero(&hdr->b_dva, sizeof (dva_t)); + hdr->b_birth = 0; + hdr->b_type = ARC_BUFC_INVALID; + hdr->b_flags = 0; + hdr->b_psize = 0; + hdr->b_lsize = 0; + hdr->b_spa = 0; + hdr->b_l1hdr.b_freeze_cksum = NULL; + hdr->b_l1hdr.b_buf = NULL; + hdr->b_l1hdr.b_bufcnt = 0; + hdr->b_l1hdr.b_byteswap = 0; + hdr->b_l1hdr.b_state = NULL; + hdr->b_l1hdr.b_arc_access = 0; + hdr->b_l1hdr.b_mru_hits = 0; + hdr->b_l1hdr.b_mru_ghost_hits = 0; + hdr->b_l1hdr.b_mfu_hits = 0; + hdr->b_l1hdr.b_mfu_ghost_hits = 0; + hdr->b_l1hdr.b_l2_hits = 0; + hdr->b_l1hdr.b_acb = NULL; + hdr->b_l1hdr.b_pabd = NULL; + + if (ocache == hdr_full_crypt_cache) { + ASSERT(!HDR_HAS_RABD(hdr)); + hdr->b_crypt_hdr.b_ot = DMU_OT_NONE; + hdr->b_crypt_hdr.b_ebufcnt = 0; + hdr->b_crypt_hdr.b_dsobj = 0; + bzero(hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN); + bzero(hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN); + bzero(hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN); + } + + buf_discard_identity(hdr); + kmem_cache_free(ocache, hdr); + + return (nhdr); +} + +/* + * This function is used by the send / receive code to convert a newly + * allocated arc_buf_t to one that is suitable for a raw encrypted write. It + * is also used to allow the root objset block to be updated without altering + * its embedded MACs. Both block types will always be uncompressed so we do not + * have to worry about compression type or psize. + */ +void +arc_convert_to_raw(arc_buf_t *buf, uint64_t dsobj, boolean_t byteorder, + dmu_object_type_t ot, const uint8_t *salt, const uint8_t *iv, + const uint8_t *mac) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + ASSERT(ot == DMU_OT_DNODE || ot == DMU_OT_OBJSET); + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); + + buf->b_flags |= (ARC_BUF_FLAG_COMPRESSED | ARC_BUF_FLAG_ENCRYPTED); + if (!HDR_PROTECTED(hdr)) + hdr = arc_hdr_realloc_crypt(hdr, B_TRUE); + hdr->b_crypt_hdr.b_dsobj = dsobj; + hdr->b_crypt_hdr.b_ot = ot; + hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ? + DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot); + if (!arc_hdr_has_uncompressed_buf(hdr)) + arc_cksum_free(hdr); + + if (salt != NULL) + bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN); + if (iv != NULL) + bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN); + if (mac != NULL) + bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN); +} + +/* + * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. + * The buf is returned thawed since we expect the consumer to modify it. + */ +arc_buf_t * +arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size) +{ + arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, + B_FALSE, ZIO_COMPRESS_OFF, 0, type, B_FALSE); + + arc_buf_t *buf = NULL; + VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE, B_FALSE, + B_FALSE, B_FALSE, &buf)); + arc_buf_thaw(buf); + + return (buf); +} + +/* + * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this + * for bufs containing metadata. + */ +arc_buf_t * +arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize, + enum zio_compress compression_type, uint8_t complevel) +{ + ASSERT3U(lsize, >, 0); + ASSERT3U(lsize, >=, psize); + ASSERT3U(compression_type, >, ZIO_COMPRESS_OFF); + ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS); + + arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, + B_FALSE, compression_type, complevel, ARC_BUFC_DATA, B_FALSE); + + arc_buf_t *buf = NULL; + VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE, + B_TRUE, B_FALSE, B_FALSE, &buf)); + arc_buf_thaw(buf); + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); + + if (!arc_buf_is_shared(buf)) { + /* + * To ensure that the hdr has the correct data in it if we call + * arc_untransform() on this buf before it's been written to + * disk, it's easiest if we just set up sharing between the + * buf and the hdr. + */ + arc_hdr_free_abd(hdr, B_FALSE); + arc_share_buf(hdr, buf); + } + + return (buf); +} + +arc_buf_t * +arc_alloc_raw_buf(spa_t *spa, void *tag, uint64_t dsobj, boolean_t byteorder, + const uint8_t *salt, const uint8_t *iv, const uint8_t *mac, + dmu_object_type_t ot, uint64_t psize, uint64_t lsize, + enum zio_compress compression_type, uint8_t complevel) +{ + arc_buf_hdr_t *hdr; + arc_buf_t *buf; + arc_buf_contents_t type = DMU_OT_IS_METADATA(ot) ? + ARC_BUFC_METADATA : ARC_BUFC_DATA; + + ASSERT3U(lsize, >, 0); + ASSERT3U(lsize, >=, psize); + ASSERT3U(compression_type, >=, ZIO_COMPRESS_OFF); + ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS); + + hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, B_TRUE, + compression_type, complevel, type, B_TRUE); + + hdr->b_crypt_hdr.b_dsobj = dsobj; + hdr->b_crypt_hdr.b_ot = ot; + hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ? + DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot); + bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN); + bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN); + bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN); + + /* + * This buffer will be considered encrypted even if the ot is not an + * encrypted type. It will become authenticated instead in + * arc_write_ready(). + */ + buf = NULL; + VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_TRUE, B_TRUE, + B_FALSE, B_FALSE, &buf)); + arc_buf_thaw(buf); + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); + + return (buf); +} + +static void +arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) +{ + l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; + l2arc_dev_t *dev = l2hdr->b_dev; + uint64_t psize = HDR_GET_PSIZE(hdr); + uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, psize); + + ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); + ASSERT(HDR_HAS_L2HDR(hdr)); + + list_remove(&dev->l2ad_buflist, hdr); + + ARCSTAT_INCR(arcstat_l2_psize, -psize); + ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); + + vdev_space_update(dev->l2ad_vdev, -asize, 0, 0); + + (void) zfs_refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), + hdr); + arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); +} + +static void +arc_hdr_destroy(arc_buf_hdr_t *hdr) +{ + if (HDR_HAS_L1HDR(hdr)) { + ASSERT(hdr->b_l1hdr.b_buf == NULL || + hdr->b_l1hdr.b_bufcnt > 0); + ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); + } + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + ASSERT(!HDR_IN_HASH_TABLE(hdr)); + + if (HDR_HAS_L2HDR(hdr)) { + l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; + boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); + + if (!buflist_held) + mutex_enter(&dev->l2ad_mtx); + + /* + * Even though we checked this conditional above, we + * need to check this again now that we have the + * l2ad_mtx. This is because we could be racing with + * another thread calling l2arc_evict() which might have + * destroyed this header's L2 portion as we were waiting + * to acquire the l2ad_mtx. If that happens, we don't + * want to re-destroy the header's L2 portion. + */ + if (HDR_HAS_L2HDR(hdr)) + arc_hdr_l2hdr_destroy(hdr); + + if (!buflist_held) + mutex_exit(&dev->l2ad_mtx); + } + + /* + * The header's identify can only be safely discarded once it is no + * longer discoverable. This requires removing it from the hash table + * and the l2arc header list. After this point the hash lock can not + * be used to protect the header. + */ + if (!HDR_EMPTY(hdr)) + buf_discard_identity(hdr); + + if (HDR_HAS_L1HDR(hdr)) { + arc_cksum_free(hdr); + + while (hdr->b_l1hdr.b_buf != NULL) + arc_buf_destroy_impl(hdr->b_l1hdr.b_buf); + + if (hdr->b_l1hdr.b_pabd != NULL) + arc_hdr_free_abd(hdr, B_FALSE); + + if (HDR_HAS_RABD(hdr)) + arc_hdr_free_abd(hdr, B_TRUE); + } + + ASSERT3P(hdr->b_hash_next, ==, NULL); + if (HDR_HAS_L1HDR(hdr)) { + ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); + ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); + + if (!HDR_PROTECTED(hdr)) { + kmem_cache_free(hdr_full_cache, hdr); + } else { + kmem_cache_free(hdr_full_crypt_cache, hdr); + } + } else { + kmem_cache_free(hdr_l2only_cache, hdr); + } +} + +void +arc_buf_destroy(arc_buf_t *buf, void* tag) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + if (hdr->b_l1hdr.b_state == arc_anon) { + ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + VERIFY0(remove_reference(hdr, NULL, tag)); + arc_hdr_destroy(hdr); + return; + } + + kmutex_t *hash_lock = HDR_LOCK(hdr); + mutex_enter(hash_lock); + + ASSERT3P(hdr, ==, buf->b_hdr); + ASSERT(hdr->b_l1hdr.b_bufcnt > 0); + ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); + ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); + ASSERT3P(buf->b_data, !=, NULL); + + (void) remove_reference(hdr, hash_lock, tag); + arc_buf_destroy_impl(buf); + mutex_exit(hash_lock); +} + +/* + * Evict the arc_buf_hdr that is provided as a parameter. The resultant + * state of the header is dependent on its state prior to entering this + * function. The following transitions are possible: + * + * - arc_mru -> arc_mru_ghost + * - arc_mfu -> arc_mfu_ghost + * - arc_mru_ghost -> arc_l2c_only + * - arc_mru_ghost -> deleted + * - arc_mfu_ghost -> arc_l2c_only + * - arc_mfu_ghost -> deleted + */ +static int64_t +arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) +{ + arc_state_t *evicted_state, *state; + int64_t bytes_evicted = 0; + int min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ? + arc_min_prescient_prefetch_ms : arc_min_prefetch_ms; + + ASSERT(MUTEX_HELD(hash_lock)); + ASSERT(HDR_HAS_L1HDR(hdr)); + + state = hdr->b_l1hdr.b_state; + if (GHOST_STATE(state)) { + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + + /* + * l2arc_write_buffers() relies on a header's L1 portion + * (i.e. its b_pabd field) during it's write phase. + * Thus, we cannot push a header onto the arc_l2c_only + * state (removing its L1 piece) until the header is + * done being written to the l2arc. + */ + if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { + ARCSTAT_BUMP(arcstat_evict_l2_skip); + return (bytes_evicted); + } + + ARCSTAT_BUMP(arcstat_deleted); + bytes_evicted += HDR_GET_LSIZE(hdr); + + DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); + + if (HDR_HAS_L2HDR(hdr)) { + ASSERT(hdr->b_l1hdr.b_pabd == NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + /* + * This buffer is cached on the 2nd Level ARC; + * don't destroy the header. + */ + arc_change_state(arc_l2c_only, hdr, hash_lock); + /* + * dropping from L1+L2 cached to L2-only, + * realloc to remove the L1 header. + */ + hdr = arc_hdr_realloc(hdr, hdr_full_cache, + hdr_l2only_cache); + } else { + arc_change_state(arc_anon, hdr, hash_lock); + arc_hdr_destroy(hdr); + } + return (bytes_evicted); + } + + ASSERT(state == arc_mru || state == arc_mfu); + evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; + + /* prefetch buffers have a minimum lifespan */ + if (HDR_IO_IN_PROGRESS(hdr) || + ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && + ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < + MSEC_TO_TICK(min_lifetime))) { + ARCSTAT_BUMP(arcstat_evict_skip); + return (bytes_evicted); + } + + ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt)); + while (hdr->b_l1hdr.b_buf) { + arc_buf_t *buf = hdr->b_l1hdr.b_buf; + if (!mutex_tryenter(&buf->b_evict_lock)) { + ARCSTAT_BUMP(arcstat_mutex_miss); + break; + } + if (buf->b_data != NULL) + bytes_evicted += HDR_GET_LSIZE(hdr); + mutex_exit(&buf->b_evict_lock); + arc_buf_destroy_impl(buf); + } + + if (HDR_HAS_L2HDR(hdr)) { + ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); + } else { + if (l2arc_write_eligible(hdr->b_spa, hdr)) { + ARCSTAT_INCR(arcstat_evict_l2_eligible, + HDR_GET_LSIZE(hdr)); + } else { + ARCSTAT_INCR(arcstat_evict_l2_ineligible, + HDR_GET_LSIZE(hdr)); + } + } + + if (hdr->b_l1hdr.b_bufcnt == 0) { + arc_cksum_free(hdr); + + bytes_evicted += arc_hdr_size(hdr); + + /* + * If this hdr is being evicted and has a compressed + * buffer then we discard it here before we change states. + * This ensures that the accounting is updated correctly + * in arc_free_data_impl(). + */ + if (hdr->b_l1hdr.b_pabd != NULL) + arc_hdr_free_abd(hdr, B_FALSE); + + if (HDR_HAS_RABD(hdr)) + arc_hdr_free_abd(hdr, B_TRUE); + + arc_change_state(evicted_state, hdr, hash_lock); + ASSERT(HDR_IN_HASH_TABLE(hdr)); + arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); + DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); + } + + return (bytes_evicted); +} + +static void +arc_set_need_free(void) +{ + ASSERT(MUTEX_HELD(&arc_evict_lock)); + int64_t remaining = arc_free_memory() - arc_sys_free / 2; + arc_evict_waiter_t *aw = list_tail(&arc_evict_waiters); + if (aw == NULL) { + arc_need_free = MAX(-remaining, 0); + } else { + arc_need_free = + MAX(-remaining, (int64_t)(aw->aew_count - arc_evict_count)); + } +} + +static uint64_t +arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, + uint64_t spa, int64_t bytes) +{ + multilist_sublist_t *mls; + uint64_t bytes_evicted = 0; + arc_buf_hdr_t *hdr; + kmutex_t *hash_lock; + int evict_count = 0; + + ASSERT3P(marker, !=, NULL); + IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); + + mls = multilist_sublist_lock(ml, idx); + + for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; + hdr = multilist_sublist_prev(mls, marker)) { + if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || + (evict_count >= zfs_arc_evict_batch_limit)) + break; + + /* + * To keep our iteration location, move the marker + * forward. Since we're not holding hdr's hash lock, we + * must be very careful and not remove 'hdr' from the + * sublist. Otherwise, other consumers might mistake the + * 'hdr' as not being on a sublist when they call the + * multilist_link_active() function (they all rely on + * the hash lock protecting concurrent insertions and + * removals). multilist_sublist_move_forward() was + * specifically implemented to ensure this is the case + * (only 'marker' will be removed and re-inserted). + */ + multilist_sublist_move_forward(mls, marker); + + /* + * The only case where the b_spa field should ever be + * zero, is the marker headers inserted by + * arc_evict_state(). It's possible for multiple threads + * to be calling arc_evict_state() concurrently (e.g. + * dsl_pool_close() and zio_inject_fault()), so we must + * skip any markers we see from these other threads. + */ + if (hdr->b_spa == 0) + continue; + + /* we're only interested in evicting buffers of a certain spa */ + if (spa != 0 && hdr->b_spa != spa) { + ARCSTAT_BUMP(arcstat_evict_skip); + continue; + } + + hash_lock = HDR_LOCK(hdr); + + /* + * We aren't calling this function from any code path + * that would already be holding a hash lock, so we're + * asserting on this assumption to be defensive in case + * this ever changes. Without this check, it would be + * possible to incorrectly increment arcstat_mutex_miss + * below (e.g. if the code changed such that we called + * this function with a hash lock held). + */ + ASSERT(!MUTEX_HELD(hash_lock)); + + if (mutex_tryenter(hash_lock)) { + uint64_t evicted = arc_evict_hdr(hdr, hash_lock); + mutex_exit(hash_lock); + + bytes_evicted += evicted; + + /* + * If evicted is zero, arc_evict_hdr() must have + * decided to skip this header, don't increment + * evict_count in this case. + */ + if (evicted != 0) + evict_count++; + + } else { + ARCSTAT_BUMP(arcstat_mutex_miss); + } + } + + multilist_sublist_unlock(mls); + + /* + * Increment the count of evicted bytes, and wake up any threads that + * are waiting for the count to reach this value. Since the list is + * ordered by ascending aew_count, we pop off the beginning of the + * list until we reach the end, or a waiter that's past the current + * "count". Doing this outside the loop reduces the number of times + * we need to acquire the global arc_evict_lock. + * + * Only wake when there's sufficient free memory in the system + * (specifically, arc_sys_free/2, which by default is a bit more than + * 1/64th of RAM). See the comments in arc_wait_for_eviction(). + */ + mutex_enter(&arc_evict_lock); + arc_evict_count += bytes_evicted; + + if ((int64_t)(arc_free_memory() - arc_sys_free / 2) > 0) { + arc_evict_waiter_t *aw; + while ((aw = list_head(&arc_evict_waiters)) != NULL && + aw->aew_count <= arc_evict_count) { + list_remove(&arc_evict_waiters, aw); + cv_broadcast(&aw->aew_cv); + } + } + arc_set_need_free(); + mutex_exit(&arc_evict_lock); + + /* + * If the ARC size is reduced from arc_c_max to arc_c_min (especially + * if the average cached block is small), eviction can be on-CPU for + * many seconds. To ensure that other threads that may be bound to + * this CPU are able to make progress, make a voluntary preemption + * call here. + */ + cond_resched(); + + return (bytes_evicted); +} + +/* + * Evict buffers from the given arc state, until we've removed the + * specified number of bytes. Move the removed buffers to the + * appropriate evict state. + * + * This function makes a "best effort". It skips over any buffers + * it can't get a hash_lock on, and so, may not catch all candidates. + * It may also return without evicting as much space as requested. + * + * If bytes is specified using the special value ARC_EVICT_ALL, this + * will evict all available (i.e. unlocked and evictable) buffers from + * the given arc state; which is used by arc_flush(). + */ +static uint64_t +arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, + arc_buf_contents_t type) +{ + uint64_t total_evicted = 0; + multilist_t *ml = state->arcs_list[type]; + int num_sublists; + arc_buf_hdr_t **markers; + + IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); + + num_sublists = multilist_get_num_sublists(ml); + + /* + * If we've tried to evict from each sublist, made some + * progress, but still have not hit the target number of bytes + * to evict, we want to keep trying. The markers allow us to + * pick up where we left off for each individual sublist, rather + * than starting from the tail each time. + */ + markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); + for (int i = 0; i < num_sublists; i++) { + multilist_sublist_t *mls; + + markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); + + /* + * A b_spa of 0 is used to indicate that this header is + * a marker. This fact is used in arc_evict_type() and + * arc_evict_state_impl(). + */ + markers[i]->b_spa = 0; + + mls = multilist_sublist_lock(ml, i); + multilist_sublist_insert_tail(mls, markers[i]); + multilist_sublist_unlock(mls); + } + + /* + * While we haven't hit our target number of bytes to evict, or + * we're evicting all available buffers. + */ + while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { + int sublist_idx = multilist_get_random_index(ml); + uint64_t scan_evicted = 0; + + /* + * Try to reduce pinned dnodes with a floor of arc_dnode_limit. + * Request that 10% of the LRUs be scanned by the superblock + * shrinker. + */ + if (type == ARC_BUFC_DATA && aggsum_compare(&astat_dnode_size, + arc_dnode_size_limit) > 0) { + arc_prune_async((aggsum_upper_bound(&astat_dnode_size) - + arc_dnode_size_limit) / sizeof (dnode_t) / + zfs_arc_dnode_reduce_percent); + } + + /* + * Start eviction using a randomly selected sublist, + * this is to try and evenly balance eviction across all + * sublists. Always starting at the same sublist + * (e.g. index 0) would cause evictions to favor certain + * sublists over others. + */ + for (int i = 0; i < num_sublists; i++) { + uint64_t bytes_remaining; + uint64_t bytes_evicted; + + if (bytes == ARC_EVICT_ALL) + bytes_remaining = ARC_EVICT_ALL; + else if (total_evicted < bytes) + bytes_remaining = bytes - total_evicted; + else + break; + + bytes_evicted = arc_evict_state_impl(ml, sublist_idx, + markers[sublist_idx], spa, bytes_remaining); + + scan_evicted += bytes_evicted; + total_evicted += bytes_evicted; + + /* we've reached the end, wrap to the beginning */ + if (++sublist_idx >= num_sublists) + sublist_idx = 0; + } + + /* + * If we didn't evict anything during this scan, we have + * no reason to believe we'll evict more during another + * scan, so break the loop. + */ + if (scan_evicted == 0) { + /* This isn't possible, let's make that obvious */ + ASSERT3S(bytes, !=, 0); + + /* + * When bytes is ARC_EVICT_ALL, the only way to + * break the loop is when scan_evicted is zero. + * In that case, we actually have evicted enough, + * so we don't want to increment the kstat. + */ + if (bytes != ARC_EVICT_ALL) { + ASSERT3S(total_evicted, <, bytes); + ARCSTAT_BUMP(arcstat_evict_not_enough); + } + + break; + } + } + + for (int i = 0; i < num_sublists; i++) { + multilist_sublist_t *mls = multilist_sublist_lock(ml, i); + multilist_sublist_remove(mls, markers[i]); + multilist_sublist_unlock(mls); + + kmem_cache_free(hdr_full_cache, markers[i]); + } + kmem_free(markers, sizeof (*markers) * num_sublists); + + return (total_evicted); +} + +/* + * Flush all "evictable" data of the given type from the arc state + * specified. This will not evict any "active" buffers (i.e. referenced). + * + * When 'retry' is set to B_FALSE, the function will make a single pass + * over the state and evict any buffers that it can. Since it doesn't + * continually retry the eviction, it might end up leaving some buffers + * in the ARC due to lock misses. + * + * When 'retry' is set to B_TRUE, the function will continually retry the + * eviction until *all* evictable buffers have been removed from the + * state. As a result, if concurrent insertions into the state are + * allowed (e.g. if the ARC isn't shutting down), this function might + * wind up in an infinite loop, continually trying to evict buffers. + */ +static uint64_t +arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, + boolean_t retry) +{ + uint64_t evicted = 0; + + while (zfs_refcount_count(&state->arcs_esize[type]) != 0) { + evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); + + if (!retry) + break; + } + + return (evicted); +} + +/* + * Evict the specified number of bytes from the state specified, + * restricting eviction to the spa and type given. This function + * prevents us from trying to evict more from a state's list than + * is "evictable", and to skip evicting altogether when passed a + * negative value for "bytes". In contrast, arc_evict_state() will + * evict everything it can, when passed a negative value for "bytes". + */ +static uint64_t +arc_evict_impl(arc_state_t *state, uint64_t spa, int64_t bytes, + arc_buf_contents_t type) +{ + int64_t delta; + + if (bytes > 0 && zfs_refcount_count(&state->arcs_esize[type]) > 0) { + delta = MIN(zfs_refcount_count(&state->arcs_esize[type]), + bytes); + return (arc_evict_state(state, spa, delta, type)); + } + + return (0); +} + +/* + * The goal of this function is to evict enough meta data buffers from the + * ARC in order to enforce the arc_meta_limit. Achieving this is slightly + * more complicated than it appears because it is common for data buffers + * to have holds on meta data buffers. In addition, dnode meta data buffers + * will be held by the dnodes in the block preventing them from being freed. + * This means we can't simply traverse the ARC and expect to always find + * enough unheld meta data buffer to release. + * + * Therefore, this function has been updated to make alternating passes + * over the ARC releasing data buffers and then newly unheld meta data + * buffers. This ensures forward progress is maintained and meta_used + * will decrease. Normally this is sufficient, but if required the ARC + * will call the registered prune callbacks causing dentry and inodes to + * be dropped from the VFS cache. This will make dnode meta data buffers + * available for reclaim. + */ +static uint64_t +arc_evict_meta_balanced(uint64_t meta_used) +{ + int64_t delta, prune = 0, adjustmnt; + uint64_t total_evicted = 0; + arc_buf_contents_t type = ARC_BUFC_DATA; + int restarts = MAX(zfs_arc_meta_adjust_restarts, 0); + +restart: + /* + * This slightly differs than the way we evict from the mru in + * arc_evict because we don't have a "target" value (i.e. no + * "meta" arc_p). As a result, I think we can completely + * cannibalize the metadata in the MRU before we evict the + * metadata from the MFU. I think we probably need to implement a + * "metadata arc_p" value to do this properly. + */ + adjustmnt = meta_used - arc_meta_limit; + + if (adjustmnt > 0 && + zfs_refcount_count(&arc_mru->arcs_esize[type]) > 0) { + delta = MIN(zfs_refcount_count(&arc_mru->arcs_esize[type]), + adjustmnt); + total_evicted += arc_evict_impl(arc_mru, 0, delta, type); + adjustmnt -= delta; + } + + /* + * We can't afford to recalculate adjustmnt here. If we do, + * new metadata buffers can sneak into the MRU or ANON lists, + * thus penalize the MFU metadata. Although the fudge factor is + * small, it has been empirically shown to be significant for + * certain workloads (e.g. creating many empty directories). As + * such, we use the original calculation for adjustmnt, and + * simply decrement the amount of data evicted from the MRU. + */ + + if (adjustmnt > 0 && + zfs_refcount_count(&arc_mfu->arcs_esize[type]) > 0) { + delta = MIN(zfs_refcount_count(&arc_mfu->arcs_esize[type]), + adjustmnt); + total_evicted += arc_evict_impl(arc_mfu, 0, delta, type); + } + + adjustmnt = meta_used - arc_meta_limit; + + if (adjustmnt > 0 && + zfs_refcount_count(&arc_mru_ghost->arcs_esize[type]) > 0) { + delta = MIN(adjustmnt, + zfs_refcount_count(&arc_mru_ghost->arcs_esize[type])); + total_evicted += arc_evict_impl(arc_mru_ghost, 0, delta, type); + adjustmnt -= delta; + } + + if (adjustmnt > 0 && + zfs_refcount_count(&arc_mfu_ghost->arcs_esize[type]) > 0) { + delta = MIN(adjustmnt, + zfs_refcount_count(&arc_mfu_ghost->arcs_esize[type])); + total_evicted += arc_evict_impl(arc_mfu_ghost, 0, delta, type); + } + + /* + * If after attempting to make the requested adjustment to the ARC + * the meta limit is still being exceeded then request that the + * higher layers drop some cached objects which have holds on ARC + * meta buffers. Requests to the upper layers will be made with + * increasingly large scan sizes until the ARC is below the limit. + */ + if (meta_used > arc_meta_limit) { + if (type == ARC_BUFC_DATA) { + type = ARC_BUFC_METADATA; + } else { + type = ARC_BUFC_DATA; + + if (zfs_arc_meta_prune) { + prune += zfs_arc_meta_prune; + arc_prune_async(prune); + } + } + + if (restarts > 0) { + restarts--; + goto restart; + } + } + return (total_evicted); +} + +/* + * Evict metadata buffers from the cache, such that arc_meta_used is + * capped by the arc_meta_limit tunable. + */ +static uint64_t +arc_evict_meta_only(uint64_t meta_used) +{ + uint64_t total_evicted = 0; + int64_t target; + + /* + * If we're over the meta limit, we want to evict enough + * metadata to get back under the meta limit. We don't want to + * evict so much that we drop the MRU below arc_p, though. If + * we're over the meta limit more than we're over arc_p, we + * evict some from the MRU here, and some from the MFU below. + */ + target = MIN((int64_t)(meta_used - arc_meta_limit), + (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) + + zfs_refcount_count(&arc_mru->arcs_size) - arc_p)); + + total_evicted += arc_evict_impl(arc_mru, 0, target, ARC_BUFC_METADATA); + + /* + * Similar to the above, we want to evict enough bytes to get us + * below the meta limit, but not so much as to drop us below the + * space allotted to the MFU (which is defined as arc_c - arc_p). + */ + target = MIN((int64_t)(meta_used - arc_meta_limit), + (int64_t)(zfs_refcount_count(&arc_mfu->arcs_size) - + (arc_c - arc_p))); + + total_evicted += arc_evict_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); + + return (total_evicted); +} + +static uint64_t +arc_evict_meta(uint64_t meta_used) +{ + if (zfs_arc_meta_strategy == ARC_STRATEGY_META_ONLY) + return (arc_evict_meta_only(meta_used)); + else + return (arc_evict_meta_balanced(meta_used)); +} + +/* + * Return the type of the oldest buffer in the given arc state + * + * This function will select a random sublist of type ARC_BUFC_DATA and + * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist + * is compared, and the type which contains the "older" buffer will be + * returned. + */ +static arc_buf_contents_t +arc_evict_type(arc_state_t *state) +{ + multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA]; + multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA]; + int data_idx = multilist_get_random_index(data_ml); + int meta_idx = multilist_get_random_index(meta_ml); + multilist_sublist_t *data_mls; + multilist_sublist_t *meta_mls; + arc_buf_contents_t type; + arc_buf_hdr_t *data_hdr; + arc_buf_hdr_t *meta_hdr; + + /* + * We keep the sublist lock until we're finished, to prevent + * the headers from being destroyed via arc_evict_state(). + */ + data_mls = multilist_sublist_lock(data_ml, data_idx); + meta_mls = multilist_sublist_lock(meta_ml, meta_idx); + + /* + * These two loops are to ensure we skip any markers that + * might be at the tail of the lists due to arc_evict_state(). + */ + + for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; + data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { + if (data_hdr->b_spa != 0) + break; + } + + for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; + meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { + if (meta_hdr->b_spa != 0) + break; + } + + if (data_hdr == NULL && meta_hdr == NULL) { + type = ARC_BUFC_DATA; + } else if (data_hdr == NULL) { + ASSERT3P(meta_hdr, !=, NULL); + type = ARC_BUFC_METADATA; + } else if (meta_hdr == NULL) { + ASSERT3P(data_hdr, !=, NULL); + type = ARC_BUFC_DATA; + } else { + ASSERT3P(data_hdr, !=, NULL); + ASSERT3P(meta_hdr, !=, NULL); + + /* The headers can't be on the sublist without an L1 header */ + ASSERT(HDR_HAS_L1HDR(data_hdr)); + ASSERT(HDR_HAS_L1HDR(meta_hdr)); + + if (data_hdr->b_l1hdr.b_arc_access < + meta_hdr->b_l1hdr.b_arc_access) { + type = ARC_BUFC_DATA; + } else { + type = ARC_BUFC_METADATA; + } + } + + multilist_sublist_unlock(meta_mls); + multilist_sublist_unlock(data_mls); + + return (type); +} + +/* + * Evict buffers from the cache, such that arc_size is capped by arc_c. + */ +static uint64_t +arc_evict(void) +{ + uint64_t total_evicted = 0; + uint64_t bytes; + int64_t target; + uint64_t asize = aggsum_value(&arc_size); + uint64_t ameta = aggsum_value(&arc_meta_used); + + /* + * If we're over arc_meta_limit, we want to correct that before + * potentially evicting data buffers below. + */ + total_evicted += arc_evict_meta(ameta); + + /* + * Adjust MRU size + * + * If we're over the target cache size, we want to evict enough + * from the list to get back to our target size. We don't want + * to evict too much from the MRU, such that it drops below + * arc_p. So, if we're over our target cache size more than + * the MRU is over arc_p, we'll evict enough to get back to + * arc_p here, and then evict more from the MFU below. + */ + target = MIN((int64_t)(asize - arc_c), + (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) + + zfs_refcount_count(&arc_mru->arcs_size) + ameta - arc_p)); + + /* + * If we're below arc_meta_min, always prefer to evict data. + * Otherwise, try to satisfy the requested number of bytes to + * evict from the type which contains older buffers; in an + * effort to keep newer buffers in the cache regardless of their + * type. If we cannot satisfy the number of bytes from this + * type, spill over into the next type. + */ + if (arc_evict_type(arc_mru) == ARC_BUFC_METADATA && + ameta > arc_meta_min) { + bytes = arc_evict_impl(arc_mru, 0, target, ARC_BUFC_METADATA); + total_evicted += bytes; + + /* + * If we couldn't evict our target number of bytes from + * metadata, we try to get the rest from data. + */ + target -= bytes; + + total_evicted += + arc_evict_impl(arc_mru, 0, target, ARC_BUFC_DATA); + } else { + bytes = arc_evict_impl(arc_mru, 0, target, ARC_BUFC_DATA); + total_evicted += bytes; + + /* + * If we couldn't evict our target number of bytes from + * data, we try to get the rest from metadata. + */ + target -= bytes; + + total_evicted += + arc_evict_impl(arc_mru, 0, target, ARC_BUFC_METADATA); + } + + /* + * Re-sum ARC stats after the first round of evictions. + */ + asize = aggsum_value(&arc_size); + ameta = aggsum_value(&arc_meta_used); + + + /* + * Adjust MFU size + * + * Now that we've tried to evict enough from the MRU to get its + * size back to arc_p, if we're still above the target cache + * size, we evict the rest from the MFU. + */ + target = asize - arc_c; + + if (arc_evict_type(arc_mfu) == ARC_BUFC_METADATA && + ameta > arc_meta_min) { + bytes = arc_evict_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); + total_evicted += bytes; + + /* + * If we couldn't evict our target number of bytes from + * metadata, we try to get the rest from data. + */ + target -= bytes; + + total_evicted += + arc_evict_impl(arc_mfu, 0, target, ARC_BUFC_DATA); + } else { + bytes = arc_evict_impl(arc_mfu, 0, target, ARC_BUFC_DATA); + total_evicted += bytes; + + /* + * If we couldn't evict our target number of bytes from + * data, we try to get the rest from data. + */ + target -= bytes; + + total_evicted += + arc_evict_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); + } + + /* + * Adjust ghost lists + * + * In addition to the above, the ARC also defines target values + * for the ghost lists. The sum of the mru list and mru ghost + * list should never exceed the target size of the cache, and + * the sum of the mru list, mfu list, mru ghost list, and mfu + * ghost list should never exceed twice the target size of the + * cache. The following logic enforces these limits on the ghost + * caches, and evicts from them as needed. + */ + target = zfs_refcount_count(&arc_mru->arcs_size) + + zfs_refcount_count(&arc_mru_ghost->arcs_size) - arc_c; + + bytes = arc_evict_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); + total_evicted += bytes; + + target -= bytes; + + total_evicted += + arc_evict_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); + + /* + * We assume the sum of the mru list and mfu list is less than + * or equal to arc_c (we enforced this above), which means we + * can use the simpler of the two equations below: + * + * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c + * mru ghost + mfu ghost <= arc_c + */ + target = zfs_refcount_count(&arc_mru_ghost->arcs_size) + + zfs_refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; + + bytes = arc_evict_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); + total_evicted += bytes; + + target -= bytes; + + total_evicted += + arc_evict_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); + + return (total_evicted); +} + +void +arc_flush(spa_t *spa, boolean_t retry) +{ + uint64_t guid = 0; + + /* + * If retry is B_TRUE, a spa must not be specified since we have + * no good way to determine if all of a spa's buffers have been + * evicted from an arc state. + */ + ASSERT(!retry || spa == 0); + + if (spa != NULL) + guid = spa_load_guid(spa); + + (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); + (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); + + (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); + (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); + + (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); + (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); + + (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); + (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); +} + +void +arc_reduce_target_size(int64_t to_free) +{ + uint64_t asize = aggsum_value(&arc_size); + + /* + * All callers want the ARC to actually evict (at least) this much + * memory. Therefore we reduce from the lower of the current size and + * the target size. This way, even if arc_c is much higher than + * arc_size (as can be the case after many calls to arc_freed(), we will + * immediately have arc_c < arc_size and therefore the arc_evict_zthr + * will evict. + */ + uint64_t c = MIN(arc_c, asize); + + if (c > to_free && c - to_free > arc_c_min) { + arc_c = c - to_free; + atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); + if (arc_p > arc_c) + arc_p = (arc_c >> 1); + ASSERT(arc_c >= arc_c_min); + ASSERT((int64_t)arc_p >= 0); + } else { + arc_c = arc_c_min; + } + + if (asize > arc_c) { + /* See comment in arc_evict_cb_check() on why lock+flag */ + mutex_enter(&arc_evict_lock); + arc_evict_needed = B_TRUE; + mutex_exit(&arc_evict_lock); + zthr_wakeup(arc_evict_zthr); + } +} + +/* + * Determine if the system is under memory pressure and is asking + * to reclaim memory. A return value of B_TRUE indicates that the system + * is under memory pressure and that the arc should adjust accordingly. + */ +boolean_t +arc_reclaim_needed(void) +{ + return (arc_available_memory() < 0); +} + +void +arc_kmem_reap_soon(void) +{ + size_t i; + kmem_cache_t *prev_cache = NULL; + kmem_cache_t *prev_data_cache = NULL; + extern kmem_cache_t *zio_buf_cache[]; + extern kmem_cache_t *zio_data_buf_cache[]; + +#ifdef _KERNEL + if ((aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) && + zfs_arc_meta_prune) { + /* + * We are exceeding our meta-data cache limit. + * Prune some entries to release holds on meta-data. + */ + arc_prune_async(zfs_arc_meta_prune); + } +#if defined(_ILP32) + /* + * Reclaim unused memory from all kmem caches. + */ + kmem_reap(); +#endif +#endif + + for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { +#if defined(_ILP32) + /* reach upper limit of cache size on 32-bit */ + if (zio_buf_cache[i] == NULL) + break; +#endif + if (zio_buf_cache[i] != prev_cache) { + prev_cache = zio_buf_cache[i]; + kmem_cache_reap_now(zio_buf_cache[i]); + } + if (zio_data_buf_cache[i] != prev_data_cache) { + prev_data_cache = zio_data_buf_cache[i]; + kmem_cache_reap_now(zio_data_buf_cache[i]); + } + } + kmem_cache_reap_now(buf_cache); + kmem_cache_reap_now(hdr_full_cache); + kmem_cache_reap_now(hdr_l2only_cache); + kmem_cache_reap_now(zfs_btree_leaf_cache); + abd_cache_reap_now(); +} + +/* ARGSUSED */ +static boolean_t +arc_evict_cb_check(void *arg, zthr_t *zthr) +{ + /* + * This is necessary so that any changes which may have been made to + * many of the zfs_arc_* module parameters will be propagated to + * their actual internal variable counterparts. Without this, + * changing those module params at runtime would have no effect. + */ + arc_tuning_update(B_FALSE); + + /* + * This is necessary in order to keep the kstat information + * up to date for tools that display kstat data such as the + * mdb ::arc dcmd and the Linux crash utility. These tools + * typically do not call kstat's update function, but simply + * dump out stats from the most recent update. Without + * this call, these commands may show stale stats for the + * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even + * with this change, the data might be up to 1 second + * out of date(the arc_evict_zthr has a maximum sleep + * time of 1 second); but that should suffice. The + * arc_state_t structures can be queried directly if more + * accurate information is needed. + */ + if (arc_ksp != NULL) + arc_ksp->ks_update(arc_ksp, KSTAT_READ); + + /* + * We have to rely on arc_wait_for_eviction() to tell us when to + * evict, rather than checking if we are overflowing here, so that we + * are sure to not leave arc_wait_for_eviction() waiting on aew_cv. + * If we have become "not overflowing" since arc_wait_for_eviction() + * checked, we need to wake it up. We could broadcast the CV here, + * but arc_wait_for_eviction() may have not yet gone to sleep. We + * would need to use a mutex to ensure that this function doesn't + * broadcast until arc_wait_for_eviction() has gone to sleep (e.g. + * the arc_evict_lock). However, the lock ordering of such a lock + * would necessarily be incorrect with respect to the zthr_lock, + * which is held before this function is called, and is held by + * arc_wait_for_eviction() when it calls zthr_wakeup(). + */ + return (arc_evict_needed); +} + +/* + * Keep arc_size under arc_c by running arc_evict which evicts data + * from the ARC. + */ +/* ARGSUSED */ +static void +arc_evict_cb(void *arg, zthr_t *zthr) +{ + uint64_t evicted = 0; + fstrans_cookie_t cookie = spl_fstrans_mark(); + + /* Evict from cache */ + evicted = arc_evict(); + + /* + * If evicted is zero, we couldn't evict anything + * via arc_evict(). This could be due to hash lock + * collisions, but more likely due to the majority of + * arc buffers being unevictable. Therefore, even if + * arc_size is above arc_c, another pass is unlikely to + * be helpful and could potentially cause us to enter an + * infinite loop. Additionally, zthr_iscancelled() is + * checked here so that if the arc is shutting down, the + * broadcast will wake any remaining arc evict waiters. + */ + mutex_enter(&arc_evict_lock); + arc_evict_needed = !zthr_iscancelled(arc_evict_zthr) && + evicted > 0 && aggsum_compare(&arc_size, arc_c) > 0; + if (!arc_evict_needed) { + /* + * We're either no longer overflowing, or we + * can't evict anything more, so we should wake + * arc_get_data_impl() sooner. + */ + arc_evict_waiter_t *aw; + while ((aw = list_remove_head(&arc_evict_waiters)) != NULL) { + cv_broadcast(&aw->aew_cv); + } + arc_set_need_free(); + } + mutex_exit(&arc_evict_lock); + spl_fstrans_unmark(cookie); +} + +/* ARGSUSED */ +static boolean_t +arc_reap_cb_check(void *arg, zthr_t *zthr) +{ + int64_t free_memory = arc_available_memory(); + + /* + * If a kmem reap is already active, don't schedule more. We must + * check for this because kmem_cache_reap_soon() won't actually + * block on the cache being reaped (this is to prevent callers from + * becoming implicitly blocked by a system-wide kmem reap -- which, + * on a system with many, many full magazines, can take minutes). + */ + if (!kmem_cache_reap_active() && free_memory < 0) { + + arc_no_grow = B_TRUE; + arc_warm = B_TRUE; + /* + * Wait at least zfs_grow_retry (default 5) seconds + * before considering growing. + */ + arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry); + return (B_TRUE); + } else if (free_memory < arc_c >> arc_no_grow_shift) { + arc_no_grow = B_TRUE; + } else if (gethrtime() >= arc_growtime) { + arc_no_grow = B_FALSE; + } + + return (B_FALSE); +} + +/* + * Keep enough free memory in the system by reaping the ARC's kmem + * caches. To cause more slabs to be reapable, we may reduce the + * target size of the cache (arc_c), causing the arc_evict_cb() + * to free more buffers. + */ +/* ARGSUSED */ +static void +arc_reap_cb(void *arg, zthr_t *zthr) +{ + int64_t free_memory; + fstrans_cookie_t cookie = spl_fstrans_mark(); + + /* + * Kick off asynchronous kmem_reap()'s of all our caches. + */ + arc_kmem_reap_soon(); + + /* + * Wait at least arc_kmem_cache_reap_retry_ms between + * arc_kmem_reap_soon() calls. Without this check it is possible to + * end up in a situation where we spend lots of time reaping + * caches, while we're near arc_c_min. Waiting here also gives the + * subsequent free memory check a chance of finding that the + * asynchronous reap has already freed enough memory, and we don't + * need to call arc_reduce_target_size(). + */ + delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000); + + /* + * Reduce the target size as needed to maintain the amount of free + * memory in the system at a fraction of the arc_size (1/128th by + * default). If oversubscribed (free_memory < 0) then reduce the + * target arc_size by the deficit amount plus the fractional + * amount. If free memory is positive but less then the fractional + * amount, reduce by what is needed to hit the fractional amount. + */ + free_memory = arc_available_memory(); + + int64_t to_free = + (arc_c >> arc_shrink_shift) - free_memory; + if (to_free > 0) { + arc_reduce_target_size(to_free); + } + spl_fstrans_unmark(cookie); +} + +#ifdef _KERNEL +/* + * Determine the amount of memory eligible for eviction contained in the + * ARC. All clean data reported by the ghost lists can always be safely + * evicted. Due to arc_c_min, the same does not hold for all clean data + * contained by the regular mru and mfu lists. + * + * In the case of the regular mru and mfu lists, we need to report as + * much clean data as possible, such that evicting that same reported + * data will not bring arc_size below arc_c_min. Thus, in certain + * circumstances, the total amount of clean data in the mru and mfu + * lists might not actually be evictable. + * + * The following two distinct cases are accounted for: + * + * 1. The sum of the amount of dirty data contained by both the mru and + * mfu lists, plus the ARC's other accounting (e.g. the anon list), + * is greater than or equal to arc_c_min. + * (i.e. amount of dirty data >= arc_c_min) + * + * This is the easy case; all clean data contained by the mru and mfu + * lists is evictable. Evicting all clean data can only drop arc_size + * to the amount of dirty data, which is greater than arc_c_min. + * + * 2. The sum of the amount of dirty data contained by both the mru and + * mfu lists, plus the ARC's other accounting (e.g. the anon list), + * is less than arc_c_min. + * (i.e. arc_c_min > amount of dirty data) + * + * 2.1. arc_size is greater than or equal arc_c_min. + * (i.e. arc_size >= arc_c_min > amount of dirty data) + * + * In this case, not all clean data from the regular mru and mfu + * lists is actually evictable; we must leave enough clean data + * to keep arc_size above arc_c_min. Thus, the maximum amount of + * evictable data from the two lists combined, is exactly the + * difference between arc_size and arc_c_min. + * + * 2.2. arc_size is less than arc_c_min + * (i.e. arc_c_min > arc_size > amount of dirty data) + * + * In this case, none of the data contained in the mru and mfu + * lists is evictable, even if it's clean. Since arc_size is + * already below arc_c_min, evicting any more would only + * increase this negative difference. + */ + +#endif /* _KERNEL */ + +/* + * Adapt arc info given the number of bytes we are trying to add and + * the state that we are coming from. This function is only called + * when we are adding new content to the cache. + */ +static void +arc_adapt(int bytes, arc_state_t *state) +{ + int mult; + uint64_t arc_p_min = (arc_c >> arc_p_min_shift); + int64_t mrug_size = zfs_refcount_count(&arc_mru_ghost->arcs_size); + int64_t mfug_size = zfs_refcount_count(&arc_mfu_ghost->arcs_size); + + if (state == arc_l2c_only) + return; + + ASSERT(bytes > 0); + /* + * Adapt the target size of the MRU list: + * - if we just hit in the MRU ghost list, then increase + * the target size of the MRU list. + * - if we just hit in the MFU ghost list, then increase + * the target size of the MFU list by decreasing the + * target size of the MRU list. + */ + if (state == arc_mru_ghost) { + mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); + if (!zfs_arc_p_dampener_disable) + mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ + + arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); + } else if (state == arc_mfu_ghost) { + uint64_t delta; + + mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); + if (!zfs_arc_p_dampener_disable) + mult = MIN(mult, 10); + + delta = MIN(bytes * mult, arc_p); + arc_p = MAX(arc_p_min, arc_p - delta); + } + ASSERT((int64_t)arc_p >= 0); + + /* + * Wake reap thread if we do not have any available memory + */ + if (arc_reclaim_needed()) { + zthr_wakeup(arc_reap_zthr); + return; + } + + if (arc_no_grow) + return; + + if (arc_c >= arc_c_max) + return; + + /* + * If we're within (2 * maxblocksize) bytes of the target + * cache size, increment the target cache size + */ + ASSERT3U(arc_c, >=, 2ULL << SPA_MAXBLOCKSHIFT); + if (aggsum_upper_bound(&arc_size) >= + arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { + atomic_add_64(&arc_c, (int64_t)bytes); + if (arc_c > arc_c_max) + arc_c = arc_c_max; + else if (state == arc_anon) + atomic_add_64(&arc_p, (int64_t)bytes); + if (arc_p > arc_c) + arc_p = arc_c; + } + ASSERT((int64_t)arc_p >= 0); +} + +/* + * Check if arc_size has grown past our upper threshold, determined by + * zfs_arc_overflow_shift. + */ +boolean_t +arc_is_overflowing(void) +{ + /* Always allow at least one block of overflow */ + int64_t overflow = MAX(SPA_MAXBLOCKSIZE, + arc_c >> zfs_arc_overflow_shift); + + /* + * We just compare the lower bound here for performance reasons. Our + * primary goals are to make sure that the arc never grows without + * bound, and that it can reach its maximum size. This check + * accomplishes both goals. The maximum amount we could run over by is + * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block + * in the ARC. In practice, that's in the tens of MB, which is low + * enough to be safe. + */ + return (aggsum_lower_bound(&arc_size) >= (int64_t)arc_c + overflow); +} + +static abd_t * +arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag, + boolean_t do_adapt) +{ + arc_buf_contents_t type = arc_buf_type(hdr); + + arc_get_data_impl(hdr, size, tag, do_adapt); + if (type == ARC_BUFC_METADATA) { + return (abd_alloc(size, B_TRUE)); + } else { + ASSERT(type == ARC_BUFC_DATA); + return (abd_alloc(size, B_FALSE)); + } +} + +static void * +arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) +{ + arc_buf_contents_t type = arc_buf_type(hdr); + + arc_get_data_impl(hdr, size, tag, B_TRUE); + if (type == ARC_BUFC_METADATA) { + return (zio_buf_alloc(size)); + } else { + ASSERT(type == ARC_BUFC_DATA); + return (zio_data_buf_alloc(size)); + } +} + +/* + * Wait for the specified amount of data (in bytes) to be evicted from the + * ARC, and for there to be sufficient free memory in the system. Waiting for + * eviction ensures that the memory used by the ARC decreases. Waiting for + * free memory ensures that the system won't run out of free pages, regardless + * of ARC behavior and settings. See arc_lowmem_init(). + */ +void +arc_wait_for_eviction(uint64_t amount) +{ + mutex_enter(&arc_evict_lock); + if (arc_is_overflowing()) { + arc_evict_needed = B_TRUE; + zthr_wakeup(arc_evict_zthr); + + if (amount != 0) { + arc_evict_waiter_t aw; + list_link_init(&aw.aew_node); + cv_init(&aw.aew_cv, NULL, CV_DEFAULT, NULL); + + arc_evict_waiter_t *last = + list_tail(&arc_evict_waiters); + if (last != NULL) { + ASSERT3U(last->aew_count, >, arc_evict_count); + aw.aew_count = last->aew_count + amount; + } else { + aw.aew_count = arc_evict_count + amount; + } + + list_insert_tail(&arc_evict_waiters, &aw); + + arc_set_need_free(); + + DTRACE_PROBE3(arc__wait__for__eviction, + uint64_t, amount, + uint64_t, arc_evict_count, + uint64_t, aw.aew_count); + + /* + * We will be woken up either when arc_evict_count + * reaches aew_count, or when the ARC is no longer + * overflowing and eviction completes. + */ + cv_wait(&aw.aew_cv, &arc_evict_lock); + + /* + * In case of "false" wakeup, we will still be on the + * list. + */ + if (list_link_active(&aw.aew_node)) + list_remove(&arc_evict_waiters, &aw); + + cv_destroy(&aw.aew_cv); + } + } + mutex_exit(&arc_evict_lock); +} + +/* + * Allocate a block and return it to the caller. If we are hitting the + * hard limit for the cache size, we must sleep, waiting for the eviction + * thread to catch up. If we're past the target size but below the hard + * limit, we'll only signal the reclaim thread and continue on. + */ +static void +arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag, + boolean_t do_adapt) +{ + arc_state_t *state = hdr->b_l1hdr.b_state; + arc_buf_contents_t type = arc_buf_type(hdr); + + if (do_adapt) + arc_adapt(size, state); + + /* + * If arc_size is currently overflowing, we must be adding data + * faster than we are evicting. To ensure we don't compound the + * problem by adding more data and forcing arc_size to grow even + * further past it's target size, we wait for the eviction thread to + * make some progress. We also wait for there to be sufficient free + * memory in the system, as measured by arc_free_memory(). + * + * Specifically, we wait for zfs_arc_eviction_pct percent of the + * requested size to be evicted. This should be more than 100%, to + * ensure that that progress is also made towards getting arc_size + * under arc_c. See the comment above zfs_arc_eviction_pct. + * + * We do the overflowing check without holding the arc_evict_lock to + * reduce lock contention in this hot path. Note that + * arc_wait_for_eviction() will acquire the lock and check again to + * ensure we are truly overflowing before blocking. + */ + if (arc_is_overflowing()) { + arc_wait_for_eviction(size * + zfs_arc_eviction_pct / 100); + } + + VERIFY3U(hdr->b_type, ==, type); + if (type == ARC_BUFC_METADATA) { + arc_space_consume(size, ARC_SPACE_META); + } else { + arc_space_consume(size, ARC_SPACE_DATA); + } + + /* + * Update the state size. Note that ghost states have a + * "ghost size" and so don't need to be updated. + */ + if (!GHOST_STATE(state)) { + + (void) zfs_refcount_add_many(&state->arcs_size, size, tag); + + /* + * If this is reached via arc_read, the link is + * protected by the hash lock. If reached via + * arc_buf_alloc, the header should not be accessed by + * any other thread. And, if reached via arc_read_done, + * the hash lock will protect it if it's found in the + * hash table; otherwise no other thread should be + * trying to [add|remove]_reference it. + */ + if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { + ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + (void) zfs_refcount_add_many(&state->arcs_esize[type], + size, tag); + } + + /* + * If we are growing the cache, and we are adding anonymous + * data, and we have outgrown arc_p, update arc_p + */ + if (aggsum_upper_bound(&arc_size) < arc_c && + hdr->b_l1hdr.b_state == arc_anon && + (zfs_refcount_count(&arc_anon->arcs_size) + + zfs_refcount_count(&arc_mru->arcs_size) > arc_p)) + arc_p = MIN(arc_c, arc_p + size); + } +} + +static void +arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag) +{ + arc_free_data_impl(hdr, size, tag); + abd_free(abd); +} + +static void +arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag) +{ + arc_buf_contents_t type = arc_buf_type(hdr); + + arc_free_data_impl(hdr, size, tag); + if (type == ARC_BUFC_METADATA) { + zio_buf_free(buf, size); + } else { + ASSERT(type == ARC_BUFC_DATA); + zio_data_buf_free(buf, size); + } +} + +/* + * Free the arc data buffer. + */ +static void +arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) +{ + arc_state_t *state = hdr->b_l1hdr.b_state; + arc_buf_contents_t type = arc_buf_type(hdr); + + /* protected by hash lock, if in the hash table */ + if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { + ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT(state != arc_anon && state != arc_l2c_only); + + (void) zfs_refcount_remove_many(&state->arcs_esize[type], + size, tag); + } + (void) zfs_refcount_remove_many(&state->arcs_size, size, tag); + + VERIFY3U(hdr->b_type, ==, type); + if (type == ARC_BUFC_METADATA) { + arc_space_return(size, ARC_SPACE_META); + } else { + ASSERT(type == ARC_BUFC_DATA); + arc_space_return(size, ARC_SPACE_DATA); + } +} + +/* + * This routine is called whenever a buffer is accessed. + * NOTE: the hash lock is dropped in this function. + */ +static void +arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) +{ + clock_t now; + + ASSERT(MUTEX_HELD(hash_lock)); + ASSERT(HDR_HAS_L1HDR(hdr)); + + if (hdr->b_l1hdr.b_state == arc_anon) { + /* + * This buffer is not in the cache, and does not + * appear in our "ghost" list. Add the new buffer + * to the MRU state. + */ + + ASSERT0(hdr->b_l1hdr.b_arc_access); + hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); + DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); + arc_change_state(arc_mru, hdr, hash_lock); + + } else if (hdr->b_l1hdr.b_state == arc_mru) { + now = ddi_get_lbolt(); + + /* + * If this buffer is here because of a prefetch, then either: + * - clear the flag if this is a "referencing" read + * (any subsequent access will bump this into the MFU state). + * or + * - move the buffer to the head of the list if this is + * another prefetch (to make it less likely to be evicted). + */ + if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { + if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { + /* link protected by hash lock */ + ASSERT(multilist_link_active( + &hdr->b_l1hdr.b_arc_node)); + } else { + arc_hdr_clear_flags(hdr, + ARC_FLAG_PREFETCH | + ARC_FLAG_PRESCIENT_PREFETCH); + atomic_inc_32(&hdr->b_l1hdr.b_mru_hits); + ARCSTAT_BUMP(arcstat_mru_hits); + } + hdr->b_l1hdr.b_arc_access = now; + return; + } + + /* + * This buffer has been "accessed" only once so far, + * but it is still in the cache. Move it to the MFU + * state. + */ + if (ddi_time_after(now, hdr->b_l1hdr.b_arc_access + + ARC_MINTIME)) { + /* + * More than 125ms have passed since we + * instantiated this buffer. Move it to the + * most frequently used state. + */ + hdr->b_l1hdr.b_arc_access = now; + DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); + arc_change_state(arc_mfu, hdr, hash_lock); + } + atomic_inc_32(&hdr->b_l1hdr.b_mru_hits); + ARCSTAT_BUMP(arcstat_mru_hits); + } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { + arc_state_t *new_state; + /* + * This buffer has been "accessed" recently, but + * was evicted from the cache. Move it to the + * MFU state. + */ + + if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { + new_state = arc_mru; + if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) { + arc_hdr_clear_flags(hdr, + ARC_FLAG_PREFETCH | + ARC_FLAG_PRESCIENT_PREFETCH); + } + DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); + } else { + new_state = arc_mfu; + DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); + } + + hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); + arc_change_state(new_state, hdr, hash_lock); + + atomic_inc_32(&hdr->b_l1hdr.b_mru_ghost_hits); + ARCSTAT_BUMP(arcstat_mru_ghost_hits); + } else if (hdr->b_l1hdr.b_state == arc_mfu) { + /* + * This buffer has been accessed more than once and is + * still in the cache. Keep it in the MFU state. + * + * NOTE: an add_reference() that occurred when we did + * the arc_read() will have kicked this off the list. + * If it was a prefetch, we will explicitly move it to + * the head of the list now. + */ + + atomic_inc_32(&hdr->b_l1hdr.b_mfu_hits); + ARCSTAT_BUMP(arcstat_mfu_hits); + hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); + } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { + arc_state_t *new_state = arc_mfu; + /* + * This buffer has been accessed more than once but has + * been evicted from the cache. Move it back to the + * MFU state. + */ + + if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { + /* + * This is a prefetch access... + * move this block back to the MRU state. + */ + new_state = arc_mru; + } + + hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); + DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); + arc_change_state(new_state, hdr, hash_lock); + + atomic_inc_32(&hdr->b_l1hdr.b_mfu_ghost_hits); + ARCSTAT_BUMP(arcstat_mfu_ghost_hits); + } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { + /* + * This buffer is on the 2nd Level ARC. + */ + + hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); + DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); + arc_change_state(arc_mfu, hdr, hash_lock); + } else { + cmn_err(CE_PANIC, "invalid arc state 0x%p", + hdr->b_l1hdr.b_state); + } +} + +/* + * This routine is called by dbuf_hold() to update the arc_access() state + * which otherwise would be skipped for entries in the dbuf cache. + */ +void +arc_buf_access(arc_buf_t *buf) +{ + mutex_enter(&buf->b_evict_lock); + arc_buf_hdr_t *hdr = buf->b_hdr; + + /* + * Avoid taking the hash_lock when possible as an optimization. + * The header must be checked again under the hash_lock in order + * to handle the case where it is concurrently being released. + */ + if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { + mutex_exit(&buf->b_evict_lock); + return; + } + + kmutex_t *hash_lock = HDR_LOCK(hdr); + mutex_enter(hash_lock); + + if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { + mutex_exit(hash_lock); + mutex_exit(&buf->b_evict_lock); + ARCSTAT_BUMP(arcstat_access_skip); + return; + } + + mutex_exit(&buf->b_evict_lock); + + ASSERT(hdr->b_l1hdr.b_state == arc_mru || + hdr->b_l1hdr.b_state == arc_mfu); + + DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); + arc_access(hdr, hash_lock); + mutex_exit(hash_lock); + + ARCSTAT_BUMP(arcstat_hits); + ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr) && !HDR_PRESCIENT_PREFETCH(hdr), + demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits); +} + +/* a generic arc_read_done_func_t which you can use */ +/* ARGSUSED */ +void +arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp, + arc_buf_t *buf, void *arg) +{ + if (buf == NULL) + return; + + bcopy(buf->b_data, arg, arc_buf_size(buf)); + arc_buf_destroy(buf, arg); +} + +/* a generic arc_read_done_func_t */ +/* ARGSUSED */ +void +arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp, + arc_buf_t *buf, void *arg) +{ + arc_buf_t **bufp = arg; + + if (buf == NULL) { + ASSERT(zio == NULL || zio->io_error != 0); + *bufp = NULL; + } else { + ASSERT(zio == NULL || zio->io_error == 0); + *bufp = buf; + ASSERT(buf->b_data != NULL); + } +} + +static void +arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) +{ + if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { + ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); + ASSERT3U(arc_hdr_get_compress(hdr), ==, ZIO_COMPRESS_OFF); + } else { + if (HDR_COMPRESSION_ENABLED(hdr)) { + ASSERT3U(arc_hdr_get_compress(hdr), ==, + BP_GET_COMPRESS(bp)); + } + ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); + ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); + ASSERT3U(!!HDR_PROTECTED(hdr), ==, BP_IS_PROTECTED(bp)); + } +} + +static void +arc_read_done(zio_t *zio) +{ + blkptr_t *bp = zio->io_bp; + arc_buf_hdr_t *hdr = zio->io_private; + kmutex_t *hash_lock = NULL; + arc_callback_t *callback_list; + arc_callback_t *acb; + boolean_t freeable = B_FALSE; + + /* + * The hdr was inserted into hash-table and removed from lists + * prior to starting I/O. We should find this header, since + * it's in the hash table, and it should be legit since it's + * not possible to evict it during the I/O. The only possible + * reason for it not to be found is if we were freed during the + * read. + */ + if (HDR_IN_HASH_TABLE(hdr)) { + arc_buf_hdr_t *found; + + ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); + ASSERT3U(hdr->b_dva.dva_word[0], ==, + BP_IDENTITY(zio->io_bp)->dva_word[0]); + ASSERT3U(hdr->b_dva.dva_word[1], ==, + BP_IDENTITY(zio->io_bp)->dva_word[1]); + + found = buf_hash_find(hdr->b_spa, zio->io_bp, &hash_lock); + + ASSERT((found == hdr && + DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || + (found == hdr && HDR_L2_READING(hdr))); + ASSERT3P(hash_lock, !=, NULL); + } + + if (BP_IS_PROTECTED(bp)) { + hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp); + hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset; + zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt, + hdr->b_crypt_hdr.b_iv); + + if (BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG) { + void *tmpbuf; + + tmpbuf = abd_borrow_buf_copy(zio->io_abd, + sizeof (zil_chain_t)); + zio_crypt_decode_mac_zil(tmpbuf, + hdr->b_crypt_hdr.b_mac); + abd_return_buf(zio->io_abd, tmpbuf, + sizeof (zil_chain_t)); + } else { + zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac); + } + } + + if (zio->io_error == 0) { + /* byteswap if necessary */ + if (BP_SHOULD_BYTESWAP(zio->io_bp)) { + if (BP_GET_LEVEL(zio->io_bp) > 0) { + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; + } else { + hdr->b_l1hdr.b_byteswap = + DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); + } + } else { + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; + } + if (!HDR_L2_READING(hdr)) { + hdr->b_complevel = zio->io_prop.zp_complevel; + } + } + + arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); + if (l2arc_noprefetch && HDR_PREFETCH(hdr)) + arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); + + callback_list = hdr->b_l1hdr.b_acb; + ASSERT3P(callback_list, !=, NULL); + + if (hash_lock && zio->io_error == 0 && + hdr->b_l1hdr.b_state == arc_anon) { + /* + * Only call arc_access on anonymous buffers. This is because + * if we've issued an I/O for an evicted buffer, we've already + * called arc_access (to prevent any simultaneous readers from + * getting confused). + */ + arc_access(hdr, hash_lock); + } + + /* + * If a read request has a callback (i.e. acb_done is not NULL), then we + * make a buf containing the data according to the parameters which were + * passed in. The implementation of arc_buf_alloc_impl() ensures that we + * aren't needlessly decompressing the data multiple times. + */ + int callback_cnt = 0; + for (acb = callback_list; acb != NULL; acb = acb->acb_next) { + if (!acb->acb_done) + continue; + + callback_cnt++; + + if (zio->io_error != 0) + continue; + + int error = arc_buf_alloc_impl(hdr, zio->io_spa, + &acb->acb_zb, acb->acb_private, acb->acb_encrypted, + acb->acb_compressed, acb->acb_noauth, B_TRUE, + &acb->acb_buf); + + /* + * Assert non-speculative zios didn't fail because an + * encryption key wasn't loaded + */ + ASSERT((zio->io_flags & ZIO_FLAG_SPECULATIVE) || + error != EACCES); + + /* + * If we failed to decrypt, report an error now (as the zio + * layer would have done if it had done the transforms). + */ + if (error == ECKSUM) { + ASSERT(BP_IS_PROTECTED(bp)); + error = SET_ERROR(EIO); + if ((zio->io_flags & ZIO_FLAG_SPECULATIVE) == 0) { + spa_log_error(zio->io_spa, &acb->acb_zb); + zfs_ereport_post(FM_EREPORT_ZFS_AUTHENTICATION, + zio->io_spa, NULL, &acb->acb_zb, zio, 0, 0); + } + } + + if (error != 0) { + /* + * Decompression or decryption failed. Set + * io_error so that when we call acb_done + * (below), we will indicate that the read + * failed. Note that in the unusual case + * where one callback is compressed and another + * uncompressed, we will mark all of them + * as failed, even though the uncompressed + * one can't actually fail. In this case, + * the hdr will not be anonymous, because + * if there are multiple callbacks, it's + * because multiple threads found the same + * arc buf in the hash table. + */ + zio->io_error = error; + } + } + + /* + * If there are multiple callbacks, we must have the hash lock, + * because the only way for multiple threads to find this hdr is + * in the hash table. This ensures that if there are multiple + * callbacks, the hdr is not anonymous. If it were anonymous, + * we couldn't use arc_buf_destroy() in the error case below. + */ + ASSERT(callback_cnt < 2 || hash_lock != NULL); + + hdr->b_l1hdr.b_acb = NULL; + arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); + if (callback_cnt == 0) + ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr)); + + ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || + callback_list != NULL); + + if (zio->io_error == 0) { + arc_hdr_verify(hdr, zio->io_bp); + } else { + arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); + if (hdr->b_l1hdr.b_state != arc_anon) + arc_change_state(arc_anon, hdr, hash_lock); + if (HDR_IN_HASH_TABLE(hdr)) + buf_hash_remove(hdr); + freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt); + } + + /* + * Broadcast before we drop the hash_lock to avoid the possibility + * that the hdr (and hence the cv) might be freed before we get to + * the cv_broadcast(). + */ + cv_broadcast(&hdr->b_l1hdr.b_cv); + + if (hash_lock != NULL) { + mutex_exit(hash_lock); + } else { + /* + * This block was freed while we waited for the read to + * complete. It has been removed from the hash table and + * moved to the anonymous state (so that it won't show up + * in the cache). + */ + ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); + freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt); + } + + /* execute each callback and free its structure */ + while ((acb = callback_list) != NULL) { + if (acb->acb_done != NULL) { + if (zio->io_error != 0 && acb->acb_buf != NULL) { + /* + * If arc_buf_alloc_impl() fails during + * decompression, the buf will still be + * allocated, and needs to be freed here. + */ + arc_buf_destroy(acb->acb_buf, + acb->acb_private); + acb->acb_buf = NULL; + } + acb->acb_done(zio, &zio->io_bookmark, zio->io_bp, + acb->acb_buf, acb->acb_private); + } + + if (acb->acb_zio_dummy != NULL) { + acb->acb_zio_dummy->io_error = zio->io_error; + zio_nowait(acb->acb_zio_dummy); + } + + callback_list = acb->acb_next; + kmem_free(acb, sizeof (arc_callback_t)); + } + + if (freeable) + arc_hdr_destroy(hdr); +} + +/* + * "Read" the block at the specified DVA (in bp) via the + * cache. If the block is found in the cache, invoke the provided + * callback immediately and return. Note that the `zio' parameter + * in the callback will be NULL in this case, since no IO was + * required. If the block is not in the cache pass the read request + * on to the spa with a substitute callback function, so that the + * requested block will be added to the cache. + * + * If a read request arrives for a block that has a read in-progress, + * either wait for the in-progress read to complete (and return the + * results); or, if this is a read with a "done" func, add a record + * to the read to invoke the "done" func when the read completes, + * and return; or just return. + * + * arc_read_done() will invoke all the requested "done" functions + * for readers of this block. + */ +int +arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, + arc_read_done_func_t *done, void *private, zio_priority_t priority, + int zio_flags, arc_flags_t *arc_flags, const zbookmark_phys_t *zb) +{ + arc_buf_hdr_t *hdr = NULL; + kmutex_t *hash_lock = NULL; + zio_t *rzio; + uint64_t guid = spa_load_guid(spa); + boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW_COMPRESS) != 0; + boolean_t encrypted_read = BP_IS_ENCRYPTED(bp) && + (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0; + boolean_t noauth_read = BP_IS_AUTHENTICATED(bp) && + (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0; + boolean_t embedded_bp = !!BP_IS_EMBEDDED(bp); + int rc = 0; + + ASSERT(!embedded_bp || + BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); + ASSERT(!BP_IS_HOLE(bp)); + ASSERT(!BP_IS_REDACTED(bp)); + + /* + * Normally SPL_FSTRANS will already be set since kernel threads which + * expect to call the DMU interfaces will set it when created. System + * calls are similarly handled by setting/cleaning the bit in the + * registered callback (module/os/.../zfs/zpl_*). + * + * External consumers such as Lustre which call the exported DMU + * interfaces may not have set SPL_FSTRANS. To avoid a deadlock + * on the hash_lock always set and clear the bit. + */ + fstrans_cookie_t cookie = spl_fstrans_mark(); +top: + if (!embedded_bp) { + /* + * Embedded BP's have no DVA and require no I/O to "read". + * Create an anonymous arc buf to back it. + */ + hdr = buf_hash_find(guid, bp, &hash_lock); + } + + /* + * Determine if we have an L1 cache hit or a cache miss. For simplicity + * we maintain encrypted data separately from compressed / uncompressed + * data. If the user is requesting raw encrypted data and we don't have + * that in the header we will read from disk to guarantee that we can + * get it even if the encryption keys aren't loaded. + */ + if (hdr != NULL && HDR_HAS_L1HDR(hdr) && (HDR_HAS_RABD(hdr) || + (hdr->b_l1hdr.b_pabd != NULL && !encrypted_read))) { + arc_buf_t *buf = NULL; + *arc_flags |= ARC_FLAG_CACHED; + + if (HDR_IO_IN_PROGRESS(hdr)) { + zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head; + + if (*arc_flags & ARC_FLAG_CACHED_ONLY) { + mutex_exit(hash_lock); + ARCSTAT_BUMP(arcstat_cached_only_in_progress); + rc = SET_ERROR(ENOENT); + goto out; + } + + ASSERT3P(head_zio, !=, NULL); + if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && + priority == ZIO_PRIORITY_SYNC_READ) { + /* + * This is a sync read that needs to wait for + * an in-flight async read. Request that the + * zio have its priority upgraded. + */ + zio_change_priority(head_zio, priority); + DTRACE_PROBE1(arc__async__upgrade__sync, + arc_buf_hdr_t *, hdr); + ARCSTAT_BUMP(arcstat_async_upgrade_sync); + } + if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { + arc_hdr_clear_flags(hdr, + ARC_FLAG_PREDICTIVE_PREFETCH); + } + + if (*arc_flags & ARC_FLAG_WAIT) { + cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); + mutex_exit(hash_lock); + goto top; + } + ASSERT(*arc_flags & ARC_FLAG_NOWAIT); + + if (done) { + arc_callback_t *acb = NULL; + + acb = kmem_zalloc(sizeof (arc_callback_t), + KM_SLEEP); + acb->acb_done = done; + acb->acb_private = private; + acb->acb_compressed = compressed_read; + acb->acb_encrypted = encrypted_read; + acb->acb_noauth = noauth_read; + acb->acb_zb = *zb; + if (pio != NULL) + acb->acb_zio_dummy = zio_null(pio, + spa, NULL, NULL, NULL, zio_flags); + + ASSERT3P(acb->acb_done, !=, NULL); + acb->acb_zio_head = head_zio; + acb->acb_next = hdr->b_l1hdr.b_acb; + hdr->b_l1hdr.b_acb = acb; + mutex_exit(hash_lock); + goto out; + } + mutex_exit(hash_lock); + goto out; + } + + ASSERT(hdr->b_l1hdr.b_state == arc_mru || + hdr->b_l1hdr.b_state == arc_mfu); + + if (done) { + if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { + /* + * This is a demand read which does not have to + * wait for i/o because we did a predictive + * prefetch i/o for it, which has completed. + */ + DTRACE_PROBE1( + arc__demand__hit__predictive__prefetch, + arc_buf_hdr_t *, hdr); + ARCSTAT_BUMP( + arcstat_demand_hit_predictive_prefetch); + arc_hdr_clear_flags(hdr, + ARC_FLAG_PREDICTIVE_PREFETCH); + } + + if (hdr->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) { + ARCSTAT_BUMP( + arcstat_demand_hit_prescient_prefetch); + arc_hdr_clear_flags(hdr, + ARC_FLAG_PRESCIENT_PREFETCH); + } + + ASSERT(!embedded_bp || !BP_IS_HOLE(bp)); + + /* Get a buf with the desired data in it. */ + rc = arc_buf_alloc_impl(hdr, spa, zb, private, + encrypted_read, compressed_read, noauth_read, + B_TRUE, &buf); + if (rc == ECKSUM) { + /* + * Convert authentication and decryption errors + * to EIO (and generate an ereport if needed) + * before leaving the ARC. + */ + rc = SET_ERROR(EIO); + if ((zio_flags & ZIO_FLAG_SPECULATIVE) == 0) { + spa_log_error(spa, zb); + zfs_ereport_post( + FM_EREPORT_ZFS_AUTHENTICATION, + spa, NULL, zb, NULL, 0, 0); + } + } + if (rc != 0) { + (void) remove_reference(hdr, hash_lock, + private); + arc_buf_destroy_impl(buf); + buf = NULL; + } + + /* assert any errors weren't due to unloaded keys */ + ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) || + rc != EACCES); + } else if (*arc_flags & ARC_FLAG_PREFETCH && + zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { + arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); + } + DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); + arc_access(hdr, hash_lock); + if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH) + arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH); + if (*arc_flags & ARC_FLAG_L2CACHE) + arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); + mutex_exit(hash_lock); + ARCSTAT_BUMP(arcstat_hits); + ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), + demand, prefetch, !HDR_ISTYPE_METADATA(hdr), + data, metadata, hits); + + if (done) + done(NULL, zb, bp, buf, private); + } else { + uint64_t lsize = BP_GET_LSIZE(bp); + uint64_t psize = BP_GET_PSIZE(bp); + arc_callback_t *acb; + vdev_t *vd = NULL; + uint64_t addr = 0; + boolean_t devw = B_FALSE; + uint64_t size; + abd_t *hdr_abd; + int alloc_flags = encrypted_read ? ARC_HDR_ALLOC_RDATA : 0; + + if (*arc_flags & ARC_FLAG_CACHED_ONLY) { + rc = SET_ERROR(ENOENT); + if (hash_lock != NULL) + mutex_exit(hash_lock); + goto out; + } + + /* + * Gracefully handle a damaged logical block size as a + * checksum error. + */ + if (lsize > spa_maxblocksize(spa)) { + rc = SET_ERROR(ECKSUM); + if (hash_lock != NULL) + mutex_exit(hash_lock); + goto out; + } + + if (hdr == NULL) { + /* + * This block is not in the cache or it has + * embedded data. + */ + arc_buf_hdr_t *exists = NULL; + arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); + hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, + BP_IS_PROTECTED(bp), BP_GET_COMPRESS(bp), 0, type, + encrypted_read); + + if (!embedded_bp) { + hdr->b_dva = *BP_IDENTITY(bp); + hdr->b_birth = BP_PHYSICAL_BIRTH(bp); + exists = buf_hash_insert(hdr, &hash_lock); + } + if (exists != NULL) { + /* somebody beat us to the hash insert */ + mutex_exit(hash_lock); + buf_discard_identity(hdr); + arc_hdr_destroy(hdr); + goto top; /* restart the IO request */ + } + } else { + /* + * This block is in the ghost cache or encrypted data + * was requested and we didn't have it. If it was + * L2-only (and thus didn't have an L1 hdr), + * we realloc the header to add an L1 hdr. + */ + if (!HDR_HAS_L1HDR(hdr)) { + hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, + hdr_full_cache); + } + + if (GHOST_STATE(hdr->b_l1hdr.b_state)) { + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + ASSERT0(zfs_refcount_count( + &hdr->b_l1hdr.b_refcnt)); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); + } else if (HDR_IO_IN_PROGRESS(hdr)) { + /* + * If this header already had an IO in progress + * and we are performing another IO to fetch + * encrypted data we must wait until the first + * IO completes so as not to confuse + * arc_read_done(). This should be very rare + * and so the performance impact shouldn't + * matter. + */ + cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); + mutex_exit(hash_lock); + goto top; + } + + /* + * This is a delicate dance that we play here. + * This hdr might be in the ghost list so we access + * it to move it out of the ghost list before we + * initiate the read. If it's a prefetch then + * it won't have a callback so we'll remove the + * reference that arc_buf_alloc_impl() created. We + * do this after we've called arc_access() to + * avoid hitting an assert in remove_reference(). + */ + arc_adapt(arc_hdr_size(hdr), hdr->b_l1hdr.b_state); + arc_access(hdr, hash_lock); + arc_hdr_alloc_abd(hdr, alloc_flags); + } + + if (encrypted_read) { + ASSERT(HDR_HAS_RABD(hdr)); + size = HDR_GET_PSIZE(hdr); + hdr_abd = hdr->b_crypt_hdr.b_rabd; + zio_flags |= ZIO_FLAG_RAW; + } else { + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + size = arc_hdr_size(hdr); + hdr_abd = hdr->b_l1hdr.b_pabd; + + if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) { + zio_flags |= ZIO_FLAG_RAW_COMPRESS; + } + + /* + * For authenticated bp's, we do not ask the ZIO layer + * to authenticate them since this will cause the entire + * IO to fail if the key isn't loaded. Instead, we + * defer authentication until arc_buf_fill(), which will + * verify the data when the key is available. + */ + if (BP_IS_AUTHENTICATED(bp)) + zio_flags |= ZIO_FLAG_RAW_ENCRYPT; + } + + if (*arc_flags & ARC_FLAG_PREFETCH && + zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) + arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); + if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH) + arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH); + if (*arc_flags & ARC_FLAG_L2CACHE) + arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); + if (BP_IS_AUTHENTICATED(bp)) + arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH); + if (BP_GET_LEVEL(bp) > 0) + arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); + if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) + arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); + ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); + + acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); + acb->acb_done = done; + acb->acb_private = private; + acb->acb_compressed = compressed_read; + acb->acb_encrypted = encrypted_read; + acb->acb_noauth = noauth_read; + acb->acb_zb = *zb; + + ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); + hdr->b_l1hdr.b_acb = acb; + arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); + + if (HDR_HAS_L2HDR(hdr) && + (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { + devw = hdr->b_l2hdr.b_dev->l2ad_writing; + addr = hdr->b_l2hdr.b_daddr; + /* + * Lock out L2ARC device removal. + */ + if (vdev_is_dead(vd) || + !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) + vd = NULL; + } + + /* + * We count both async reads and scrub IOs as asynchronous so + * that both can be upgraded in the event of a cache hit while + * the read IO is still in-flight. + */ + if (priority == ZIO_PRIORITY_ASYNC_READ || + priority == ZIO_PRIORITY_SCRUB) + arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); + else + arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); + + /* + * At this point, we have a level 1 cache miss or a blkptr + * with embedded data. Try again in L2ARC if possible. + */ + ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); + + /* + * Skip ARC stat bump for block pointers with embedded + * data. The data are read from the blkptr itself via + * decode_embedded_bp_compressed(). + */ + if (!embedded_bp) { + DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, + blkptr_t *, bp, uint64_t, lsize, + zbookmark_phys_t *, zb); + ARCSTAT_BUMP(arcstat_misses); + ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), + demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, + metadata, misses); + } + + if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { + /* + * Read from the L2ARC if the following are true: + * 1. The L2ARC vdev was previously cached. + * 2. This buffer still has L2ARC metadata. + * 3. This buffer isn't currently writing to the L2ARC. + * 4. The L2ARC entry wasn't evicted, which may + * also have invalidated the vdev. + * 5. This isn't prefetch and l2arc_noprefetch is set. + */ + if (HDR_HAS_L2HDR(hdr) && + !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && + !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { + l2arc_read_callback_t *cb; + abd_t *abd; + uint64_t asize; + + DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); + ARCSTAT_BUMP(arcstat_l2_hits); + atomic_inc_32(&hdr->b_l2hdr.b_hits); + + cb = kmem_zalloc(sizeof (l2arc_read_callback_t), + KM_SLEEP); + cb->l2rcb_hdr = hdr; + cb->l2rcb_bp = *bp; + cb->l2rcb_zb = *zb; + cb->l2rcb_flags = zio_flags; + + /* + * When Compressed ARC is disabled, but the + * L2ARC block is compressed, arc_hdr_size() + * will have returned LSIZE rather than PSIZE. + */ + if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && + !HDR_COMPRESSION_ENABLED(hdr) && + HDR_GET_PSIZE(hdr) != 0) { + size = HDR_GET_PSIZE(hdr); + } + + asize = vdev_psize_to_asize(vd, size); + if (asize != size) { + abd = abd_alloc_for_io(asize, + HDR_ISTYPE_METADATA(hdr)); + cb->l2rcb_abd = abd; + } else { + abd = hdr_abd; + } + + ASSERT(addr >= VDEV_LABEL_START_SIZE && + addr + asize <= vd->vdev_psize - + VDEV_LABEL_END_SIZE); + + /* + * l2arc read. The SCL_L2ARC lock will be + * released by l2arc_read_done(). + * Issue a null zio if the underlying buffer + * was squashed to zero size by compression. + */ + ASSERT3U(arc_hdr_get_compress(hdr), !=, + ZIO_COMPRESS_EMPTY); + rzio = zio_read_phys(pio, vd, addr, + asize, abd, + ZIO_CHECKSUM_OFF, + l2arc_read_done, cb, priority, + zio_flags | ZIO_FLAG_DONT_CACHE | + ZIO_FLAG_CANFAIL | + ZIO_FLAG_DONT_PROPAGATE | + ZIO_FLAG_DONT_RETRY, B_FALSE); + acb->acb_zio_head = rzio; + + if (hash_lock != NULL) + mutex_exit(hash_lock); + + DTRACE_PROBE2(l2arc__read, vdev_t *, vd, + zio_t *, rzio); + ARCSTAT_INCR(arcstat_l2_read_bytes, + HDR_GET_PSIZE(hdr)); + + if (*arc_flags & ARC_FLAG_NOWAIT) { + zio_nowait(rzio); + goto out; + } + + ASSERT(*arc_flags & ARC_FLAG_WAIT); + if (zio_wait(rzio) == 0) + goto out; + + /* l2arc read error; goto zio_read() */ + if (hash_lock != NULL) + mutex_enter(hash_lock); + } else { + DTRACE_PROBE1(l2arc__miss, + arc_buf_hdr_t *, hdr); + ARCSTAT_BUMP(arcstat_l2_misses); + if (HDR_L2_WRITING(hdr)) + ARCSTAT_BUMP(arcstat_l2_rw_clash); + spa_config_exit(spa, SCL_L2ARC, vd); + } + } else { + if (vd != NULL) + spa_config_exit(spa, SCL_L2ARC, vd); + /* + * Skip ARC stat bump for block pointers with + * embedded data. The data are read from the blkptr + * itself via decode_embedded_bp_compressed(). + */ + if (l2arc_ndev != 0 && !embedded_bp) { + DTRACE_PROBE1(l2arc__miss, + arc_buf_hdr_t *, hdr); + ARCSTAT_BUMP(arcstat_l2_misses); + } + } + + rzio = zio_read(pio, spa, bp, hdr_abd, size, + arc_read_done, hdr, priority, zio_flags, zb); + acb->acb_zio_head = rzio; + + if (hash_lock != NULL) + mutex_exit(hash_lock); + + if (*arc_flags & ARC_FLAG_WAIT) { + rc = zio_wait(rzio); + goto out; + } + + ASSERT(*arc_flags & ARC_FLAG_NOWAIT); + zio_nowait(rzio); + } + +out: + /* embedded bps don't actually go to disk */ + if (!embedded_bp) + spa_read_history_add(spa, zb, *arc_flags); + spl_fstrans_unmark(cookie); + return (rc); +} + +arc_prune_t * +arc_add_prune_callback(arc_prune_func_t *func, void *private) +{ + arc_prune_t *p; + + p = kmem_alloc(sizeof (*p), KM_SLEEP); + p->p_pfunc = func; + p->p_private = private; + list_link_init(&p->p_node); + zfs_refcount_create(&p->p_refcnt); + + mutex_enter(&arc_prune_mtx); + zfs_refcount_add(&p->p_refcnt, &arc_prune_list); + list_insert_head(&arc_prune_list, p); + mutex_exit(&arc_prune_mtx); + + return (p); +} + +void +arc_remove_prune_callback(arc_prune_t *p) +{ + boolean_t wait = B_FALSE; + mutex_enter(&arc_prune_mtx); + list_remove(&arc_prune_list, p); + if (zfs_refcount_remove(&p->p_refcnt, &arc_prune_list) > 0) + wait = B_TRUE; + mutex_exit(&arc_prune_mtx); + + /* wait for arc_prune_task to finish */ + if (wait) + taskq_wait_outstanding(arc_prune_taskq, 0); + ASSERT0(zfs_refcount_count(&p->p_refcnt)); + zfs_refcount_destroy(&p->p_refcnt); + kmem_free(p, sizeof (*p)); +} + +/* + * Notify the arc that a block was freed, and thus will never be used again. + */ +void +arc_freed(spa_t *spa, const blkptr_t *bp) +{ + arc_buf_hdr_t *hdr; + kmutex_t *hash_lock; + uint64_t guid = spa_load_guid(spa); + + ASSERT(!BP_IS_EMBEDDED(bp)); + + hdr = buf_hash_find(guid, bp, &hash_lock); + if (hdr == NULL) + return; + + /* + * We might be trying to free a block that is still doing I/O + * (i.e. prefetch) or has a reference (i.e. a dedup-ed, + * dmu_sync-ed block). If this block is being prefetched, then it + * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr + * until the I/O completes. A block may also have a reference if it is + * part of a dedup-ed, dmu_synced write. The dmu_sync() function would + * have written the new block to its final resting place on disk but + * without the dedup flag set. This would have left the hdr in the MRU + * state and discoverable. When the txg finally syncs it detects that + * the block was overridden in open context and issues an override I/O. + * Since this is a dedup block, the override I/O will determine if the + * block is already in the DDT. If so, then it will replace the io_bp + * with the bp from the DDT and allow the I/O to finish. When the I/O + * reaches the done callback, dbuf_write_override_done, it will + * check to see if the io_bp and io_bp_override are identical. + * If they are not, then it indicates that the bp was replaced with + * the bp in the DDT and the override bp is freed. This allows + * us to arrive here with a reference on a block that is being + * freed. So if we have an I/O in progress, or a reference to + * this hdr, then we don't destroy the hdr. + */ + if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && + zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { + arc_change_state(arc_anon, hdr, hash_lock); + arc_hdr_destroy(hdr); + mutex_exit(hash_lock); + } else { + mutex_exit(hash_lock); + } + +} + +/* + * Release this buffer from the cache, making it an anonymous buffer. This + * must be done after a read and prior to modifying the buffer contents. + * If the buffer has more than one reference, we must make + * a new hdr for the buffer. + */ +void +arc_release(arc_buf_t *buf, void *tag) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + + /* + * It would be nice to assert that if its DMU metadata (level > + * 0 || it's the dnode file), then it must be syncing context. + * But we don't know that information at this level. + */ + + mutex_enter(&buf->b_evict_lock); + + ASSERT(HDR_HAS_L1HDR(hdr)); + + /* + * We don't grab the hash lock prior to this check, because if + * the buffer's header is in the arc_anon state, it won't be + * linked into the hash table. + */ + if (hdr->b_l1hdr.b_state == arc_anon) { + mutex_exit(&buf->b_evict_lock); + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + ASSERT(!HDR_IN_HASH_TABLE(hdr)); + ASSERT(!HDR_HAS_L2HDR(hdr)); + ASSERT(HDR_EMPTY(hdr)); + + ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); + ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); + ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); + + hdr->b_l1hdr.b_arc_access = 0; + + /* + * If the buf is being overridden then it may already + * have a hdr that is not empty. + */ + buf_discard_identity(hdr); + arc_buf_thaw(buf); + + return; + } + + kmutex_t *hash_lock = HDR_LOCK(hdr); + mutex_enter(hash_lock); + + /* + * This assignment is only valid as long as the hash_lock is + * held, we must be careful not to reference state or the + * b_state field after dropping the lock. + */ + arc_state_t *state = hdr->b_l1hdr.b_state; + ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); + ASSERT3P(state, !=, arc_anon); + + /* this buffer is not on any list */ + ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0); + + if (HDR_HAS_L2HDR(hdr)) { + mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); + + /* + * We have to recheck this conditional again now that + * we're holding the l2ad_mtx to prevent a race with + * another thread which might be concurrently calling + * l2arc_evict(). In that case, l2arc_evict() might have + * destroyed the header's L2 portion as we were waiting + * to acquire the l2ad_mtx. + */ + if (HDR_HAS_L2HDR(hdr)) + arc_hdr_l2hdr_destroy(hdr); + + mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); + } + + /* + * Do we have more than one buf? + */ + if (hdr->b_l1hdr.b_bufcnt > 1) { + arc_buf_hdr_t *nhdr; + uint64_t spa = hdr->b_spa; + uint64_t psize = HDR_GET_PSIZE(hdr); + uint64_t lsize = HDR_GET_LSIZE(hdr); + boolean_t protected = HDR_PROTECTED(hdr); + enum zio_compress compress = arc_hdr_get_compress(hdr); + arc_buf_contents_t type = arc_buf_type(hdr); + VERIFY3U(hdr->b_type, ==, type); + + ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); + (void) remove_reference(hdr, hash_lock, tag); + + if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) { + ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); + ASSERT(ARC_BUF_LAST(buf)); + } + + /* + * Pull the data off of this hdr and attach it to + * a new anonymous hdr. Also find the last buffer + * in the hdr's buffer list. + */ + arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); + ASSERT3P(lastbuf, !=, NULL); + + /* + * If the current arc_buf_t and the hdr are sharing their data + * buffer, then we must stop sharing that block. + */ + if (arc_buf_is_shared(buf)) { + ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); + VERIFY(!arc_buf_is_shared(lastbuf)); + + /* + * First, sever the block sharing relationship between + * buf and the arc_buf_hdr_t. + */ + arc_unshare_buf(hdr, buf); + + /* + * Now we need to recreate the hdr's b_pabd. Since we + * have lastbuf handy, we try to share with it, but if + * we can't then we allocate a new b_pabd and copy the + * data from buf into it. + */ + if (arc_can_share(hdr, lastbuf)) { + arc_share_buf(hdr, lastbuf); + } else { + arc_hdr_alloc_abd(hdr, ARC_HDR_DO_ADAPT); + abd_copy_from_buf(hdr->b_l1hdr.b_pabd, + buf->b_data, psize); + } + VERIFY3P(lastbuf->b_data, !=, NULL); + } else if (HDR_SHARED_DATA(hdr)) { + /* + * Uncompressed shared buffers are always at the end + * of the list. Compressed buffers don't have the + * same requirements. This makes it hard to + * simply assert that the lastbuf is shared so + * we rely on the hdr's compression flags to determine + * if we have a compressed, shared buffer. + */ + ASSERT(arc_buf_is_shared(lastbuf) || + arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF); + ASSERT(!ARC_BUF_SHARED(buf)); + } + + ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr)); + ASSERT3P(state, !=, arc_l2c_only); + + (void) zfs_refcount_remove_many(&state->arcs_size, + arc_buf_size(buf), buf); + + if (zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { + ASSERT3P(state, !=, arc_l2c_only); + (void) zfs_refcount_remove_many( + &state->arcs_esize[type], + arc_buf_size(buf), buf); + } + + hdr->b_l1hdr.b_bufcnt -= 1; + if (ARC_BUF_ENCRYPTED(buf)) + hdr->b_crypt_hdr.b_ebufcnt -= 1; + + arc_cksum_verify(buf); + arc_buf_unwatch(buf); + + /* if this is the last uncompressed buf free the checksum */ + if (!arc_hdr_has_uncompressed_buf(hdr)) + arc_cksum_free(hdr); + + mutex_exit(hash_lock); + + /* + * Allocate a new hdr. The new hdr will contain a b_pabd + * buffer which will be freed in arc_write(). + */ + nhdr = arc_hdr_alloc(spa, psize, lsize, protected, + compress, hdr->b_complevel, type, HDR_HAS_RABD(hdr)); + ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); + ASSERT0(nhdr->b_l1hdr.b_bufcnt); + ASSERT0(zfs_refcount_count(&nhdr->b_l1hdr.b_refcnt)); + VERIFY3U(nhdr->b_type, ==, type); + ASSERT(!HDR_SHARED_DATA(nhdr)); + + nhdr->b_l1hdr.b_buf = buf; + nhdr->b_l1hdr.b_bufcnt = 1; + if (ARC_BUF_ENCRYPTED(buf)) + nhdr->b_crypt_hdr.b_ebufcnt = 1; + nhdr->b_l1hdr.b_mru_hits = 0; + nhdr->b_l1hdr.b_mru_ghost_hits = 0; + nhdr->b_l1hdr.b_mfu_hits = 0; + nhdr->b_l1hdr.b_mfu_ghost_hits = 0; + nhdr->b_l1hdr.b_l2_hits = 0; + (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); + buf->b_hdr = nhdr; + + mutex_exit(&buf->b_evict_lock); + (void) zfs_refcount_add_many(&arc_anon->arcs_size, + arc_buf_size(buf), buf); + } else { + mutex_exit(&buf->b_evict_lock); + ASSERT(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); + /* protected by hash lock, or hdr is on arc_anon */ + ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + hdr->b_l1hdr.b_mru_hits = 0; + hdr->b_l1hdr.b_mru_ghost_hits = 0; + hdr->b_l1hdr.b_mfu_hits = 0; + hdr->b_l1hdr.b_mfu_ghost_hits = 0; + hdr->b_l1hdr.b_l2_hits = 0; + arc_change_state(arc_anon, hdr, hash_lock); + hdr->b_l1hdr.b_arc_access = 0; + + mutex_exit(hash_lock); + buf_discard_identity(hdr); + arc_buf_thaw(buf); + } +} + +int +arc_released(arc_buf_t *buf) +{ + int released; + + mutex_enter(&buf->b_evict_lock); + released = (buf->b_data != NULL && + buf->b_hdr->b_l1hdr.b_state == arc_anon); + mutex_exit(&buf->b_evict_lock); + return (released); +} + +#ifdef ZFS_DEBUG +int +arc_referenced(arc_buf_t *buf) +{ + int referenced; + + mutex_enter(&buf->b_evict_lock); + referenced = (zfs_refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); + mutex_exit(&buf->b_evict_lock); + return (referenced); +} +#endif + +static void +arc_write_ready(zio_t *zio) +{ + arc_write_callback_t *callback = zio->io_private; + arc_buf_t *buf = callback->awcb_buf; + arc_buf_hdr_t *hdr = buf->b_hdr; + blkptr_t *bp = zio->io_bp; + uint64_t psize = BP_IS_HOLE(bp) ? 0 : BP_GET_PSIZE(bp); + fstrans_cookie_t cookie = spl_fstrans_mark(); + + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(!zfs_refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); + ASSERT(hdr->b_l1hdr.b_bufcnt > 0); + + /* + * If we're reexecuting this zio because the pool suspended, then + * cleanup any state that was previously set the first time the + * callback was invoked. + */ + if (zio->io_flags & ZIO_FLAG_REEXECUTED) { + arc_cksum_free(hdr); + arc_buf_unwatch(buf); + if (hdr->b_l1hdr.b_pabd != NULL) { + if (arc_buf_is_shared(buf)) { + arc_unshare_buf(hdr, buf); + } else { + arc_hdr_free_abd(hdr, B_FALSE); + } + } + + if (HDR_HAS_RABD(hdr)) + arc_hdr_free_abd(hdr, B_TRUE); + } + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(!HDR_HAS_RABD(hdr)); + ASSERT(!HDR_SHARED_DATA(hdr)); + ASSERT(!arc_buf_is_shared(buf)); + + callback->awcb_ready(zio, buf, callback->awcb_private); + + if (HDR_IO_IN_PROGRESS(hdr)) + ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); + + arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); + + if (BP_IS_PROTECTED(bp) != !!HDR_PROTECTED(hdr)) + hdr = arc_hdr_realloc_crypt(hdr, BP_IS_PROTECTED(bp)); + + if (BP_IS_PROTECTED(bp)) { + /* ZIL blocks are written through zio_rewrite */ + ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG); + ASSERT(HDR_PROTECTED(hdr)); + + if (BP_SHOULD_BYTESWAP(bp)) { + if (BP_GET_LEVEL(bp) > 0) { + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; + } else { + hdr->b_l1hdr.b_byteswap = + DMU_OT_BYTESWAP(BP_GET_TYPE(bp)); + } + } else { + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; + } + + hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp); + hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset; + zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt, + hdr->b_crypt_hdr.b_iv); + zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac); + } + + /* + * If this block was written for raw encryption but the zio layer + * ended up only authenticating it, adjust the buffer flags now. + */ + if (BP_IS_AUTHENTICATED(bp) && ARC_BUF_ENCRYPTED(buf)) { + arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH); + buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED; + if (BP_GET_COMPRESS(bp) == ZIO_COMPRESS_OFF) + buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; + } else if (BP_IS_HOLE(bp) && ARC_BUF_ENCRYPTED(buf)) { + buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED; + buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; + } + + /* this must be done after the buffer flags are adjusted */ + arc_cksum_compute(buf); + + enum zio_compress compress; + if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { + compress = ZIO_COMPRESS_OFF; + } else { + ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); + compress = BP_GET_COMPRESS(bp); + } + HDR_SET_PSIZE(hdr, psize); + arc_hdr_set_compress(hdr, compress); + hdr->b_complevel = zio->io_prop.zp_complevel; + + if (zio->io_error != 0 || psize == 0) + goto out; + + /* + * Fill the hdr with data. If the buffer is encrypted we have no choice + * but to copy the data into b_radb. If the hdr is compressed, the data + * we want is available from the zio, otherwise we can take it from + * the buf. + * + * We might be able to share the buf's data with the hdr here. However, + * doing so would cause the ARC to be full of linear ABDs if we write a + * lot of shareable data. As a compromise, we check whether scattered + * ABDs are allowed, and assume that if they are then the user wants + * the ARC to be primarily filled with them regardless of the data being + * written. Therefore, if they're allowed then we allocate one and copy + * the data into it; otherwise, we share the data directly if we can. + */ + if (ARC_BUF_ENCRYPTED(buf)) { + ASSERT3U(psize, >, 0); + ASSERT(ARC_BUF_COMPRESSED(buf)); + arc_hdr_alloc_abd(hdr, ARC_HDR_DO_ADAPT|ARC_HDR_ALLOC_RDATA); + abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize); + } else if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) { + /* + * Ideally, we would always copy the io_abd into b_pabd, but the + * user may have disabled compressed ARC, thus we must check the + * hdr's compression setting rather than the io_bp's. + */ + if (BP_IS_ENCRYPTED(bp)) { + ASSERT3U(psize, >, 0); + arc_hdr_alloc_abd(hdr, + ARC_HDR_DO_ADAPT|ARC_HDR_ALLOC_RDATA); + abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize); + } else if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF && + !ARC_BUF_COMPRESSED(buf)) { + ASSERT3U(psize, >, 0); + arc_hdr_alloc_abd(hdr, ARC_HDR_DO_ADAPT); + abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize); + } else { + ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr)); + arc_hdr_alloc_abd(hdr, ARC_HDR_DO_ADAPT); + abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data, + arc_buf_size(buf)); + } + } else { + ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd)); + ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf)); + ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); + + arc_share_buf(hdr, buf); + } + +out: + arc_hdr_verify(hdr, bp); + spl_fstrans_unmark(cookie); +} + +static void +arc_write_children_ready(zio_t *zio) +{ + arc_write_callback_t *callback = zio->io_private; + arc_buf_t *buf = callback->awcb_buf; + + callback->awcb_children_ready(zio, buf, callback->awcb_private); +} + +/* + * The SPA calls this callback for each physical write that happens on behalf + * of a logical write. See the comment in dbuf_write_physdone() for details. + */ +static void +arc_write_physdone(zio_t *zio) +{ + arc_write_callback_t *cb = zio->io_private; + if (cb->awcb_physdone != NULL) + cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); +} + +static void +arc_write_done(zio_t *zio) +{ + arc_write_callback_t *callback = zio->io_private; + arc_buf_t *buf = callback->awcb_buf; + arc_buf_hdr_t *hdr = buf->b_hdr; + + ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); + + if (zio->io_error == 0) { + arc_hdr_verify(hdr, zio->io_bp); + + if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { + buf_discard_identity(hdr); + } else { + hdr->b_dva = *BP_IDENTITY(zio->io_bp); + hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); + } + } else { + ASSERT(HDR_EMPTY(hdr)); + } + + /* + * If the block to be written was all-zero or compressed enough to be + * embedded in the BP, no write was performed so there will be no + * dva/birth/checksum. The buffer must therefore remain anonymous + * (and uncached). + */ + if (!HDR_EMPTY(hdr)) { + arc_buf_hdr_t *exists; + kmutex_t *hash_lock; + + ASSERT3U(zio->io_error, ==, 0); + + arc_cksum_verify(buf); + + exists = buf_hash_insert(hdr, &hash_lock); + if (exists != NULL) { + /* + * This can only happen if we overwrite for + * sync-to-convergence, because we remove + * buffers from the hash table when we arc_free(). + */ + if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { + if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) + panic("bad overwrite, hdr=%p exists=%p", + (void *)hdr, (void *)exists); + ASSERT(zfs_refcount_is_zero( + &exists->b_l1hdr.b_refcnt)); + arc_change_state(arc_anon, exists, hash_lock); + arc_hdr_destroy(exists); + mutex_exit(hash_lock); + exists = buf_hash_insert(hdr, &hash_lock); + ASSERT3P(exists, ==, NULL); + } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { + /* nopwrite */ + ASSERT(zio->io_prop.zp_nopwrite); + if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) + panic("bad nopwrite, hdr=%p exists=%p", + (void *)hdr, (void *)exists); + } else { + /* Dedup */ + ASSERT(hdr->b_l1hdr.b_bufcnt == 1); + ASSERT(hdr->b_l1hdr.b_state == arc_anon); + ASSERT(BP_GET_DEDUP(zio->io_bp)); + ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); + } + } + arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); + /* if it's not anon, we are doing a scrub */ + if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) + arc_access(hdr, hash_lock); + mutex_exit(hash_lock); + } else { + arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); + } + + ASSERT(!zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + callback->awcb_done(zio, buf, callback->awcb_private); + + abd_put(zio->io_abd); + kmem_free(callback, sizeof (arc_write_callback_t)); +} + +zio_t * +arc_write(zio_t *pio, spa_t *spa, uint64_t txg, + blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, + const zio_prop_t *zp, arc_write_done_func_t *ready, + arc_write_done_func_t *children_ready, arc_write_done_func_t *physdone, + arc_write_done_func_t *done, void *private, zio_priority_t priority, + int zio_flags, const zbookmark_phys_t *zb) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + arc_write_callback_t *callback; + zio_t *zio; + zio_prop_t localprop = *zp; + + ASSERT3P(ready, !=, NULL); + ASSERT3P(done, !=, NULL); + ASSERT(!HDR_IO_ERROR(hdr)); + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); + ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); + if (l2arc) + arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); + + if (ARC_BUF_ENCRYPTED(buf)) { + ASSERT(ARC_BUF_COMPRESSED(buf)); + localprop.zp_encrypt = B_TRUE; + localprop.zp_compress = HDR_GET_COMPRESS(hdr); + localprop.zp_complevel = hdr->b_complevel; + localprop.zp_byteorder = + (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ? + ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER; + bcopy(hdr->b_crypt_hdr.b_salt, localprop.zp_salt, + ZIO_DATA_SALT_LEN); + bcopy(hdr->b_crypt_hdr.b_iv, localprop.zp_iv, + ZIO_DATA_IV_LEN); + bcopy(hdr->b_crypt_hdr.b_mac, localprop.zp_mac, + ZIO_DATA_MAC_LEN); + if (DMU_OT_IS_ENCRYPTED(localprop.zp_type)) { + localprop.zp_nopwrite = B_FALSE; + localprop.zp_copies = + MIN(localprop.zp_copies, SPA_DVAS_PER_BP - 1); + } + zio_flags |= ZIO_FLAG_RAW; + } else if (ARC_BUF_COMPRESSED(buf)) { + ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf)); + localprop.zp_compress = HDR_GET_COMPRESS(hdr); + localprop.zp_complevel = hdr->b_complevel; + zio_flags |= ZIO_FLAG_RAW_COMPRESS; + } + callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); + callback->awcb_ready = ready; + callback->awcb_children_ready = children_ready; + callback->awcb_physdone = physdone; + callback->awcb_done = done; + callback->awcb_private = private; + callback->awcb_buf = buf; + + /* + * The hdr's b_pabd is now stale, free it now. A new data block + * will be allocated when the zio pipeline calls arc_write_ready(). + */ + if (hdr->b_l1hdr.b_pabd != NULL) { + /* + * If the buf is currently sharing the data block with + * the hdr then we need to break that relationship here. + * The hdr will remain with a NULL data pointer and the + * buf will take sole ownership of the block. + */ + if (arc_buf_is_shared(buf)) { + arc_unshare_buf(hdr, buf); + } else { + arc_hdr_free_abd(hdr, B_FALSE); + } + VERIFY3P(buf->b_data, !=, NULL); + } + + if (HDR_HAS_RABD(hdr)) + arc_hdr_free_abd(hdr, B_TRUE); + + if (!(zio_flags & ZIO_FLAG_RAW)) + arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); + + ASSERT(!arc_buf_is_shared(buf)); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + + zio = zio_write(pio, spa, txg, bp, + abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)), + HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready, + (children_ready != NULL) ? arc_write_children_ready : NULL, + arc_write_physdone, arc_write_done, callback, + priority, zio_flags, zb); + + return (zio); +} + +void +arc_tempreserve_clear(uint64_t reserve) +{ + atomic_add_64(&arc_tempreserve, -reserve); + ASSERT((int64_t)arc_tempreserve >= 0); +} + +int +arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg) +{ + int error; + uint64_t anon_size; + + if (!arc_no_grow && + reserve > arc_c/4 && + reserve * 4 > (2ULL << SPA_MAXBLOCKSHIFT)) + arc_c = MIN(arc_c_max, reserve * 4); + + /* + * Throttle when the calculated memory footprint for the TXG + * exceeds the target ARC size. + */ + if (reserve > arc_c) { + DMU_TX_STAT_BUMP(dmu_tx_memory_reserve); + return (SET_ERROR(ERESTART)); + } + + /* + * Don't count loaned bufs as in flight dirty data to prevent long + * network delays from blocking transactions that are ready to be + * assigned to a txg. + */ + + /* assert that it has not wrapped around */ + ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); + + anon_size = MAX((int64_t)(zfs_refcount_count(&arc_anon->arcs_size) - + arc_loaned_bytes), 0); + + /* + * Writes will, almost always, require additional memory allocations + * in order to compress/encrypt/etc the data. We therefore need to + * make sure that there is sufficient available memory for this. + */ + error = arc_memory_throttle(spa, reserve, txg); + if (error != 0) + return (error); + + /* + * Throttle writes when the amount of dirty data in the cache + * gets too large. We try to keep the cache less than half full + * of dirty blocks so that our sync times don't grow too large. + * + * In the case of one pool being built on another pool, we want + * to make sure we don't end up throttling the lower (backing) + * pool when the upper pool is the majority contributor to dirty + * data. To insure we make forward progress during throttling, we + * also check the current pool's net dirty data and only throttle + * if it exceeds zfs_arc_pool_dirty_percent of the anonymous dirty + * data in the cache. + * + * Note: if two requests come in concurrently, we might let them + * both succeed, when one of them should fail. Not a huge deal. + */ + uint64_t total_dirty = reserve + arc_tempreserve + anon_size; + uint64_t spa_dirty_anon = spa_dirty_data(spa); + + if (total_dirty > arc_c * zfs_arc_dirty_limit_percent / 100 && + anon_size > arc_c * zfs_arc_anon_limit_percent / 100 && + spa_dirty_anon > anon_size * zfs_arc_pool_dirty_percent / 100) { +#ifdef ZFS_DEBUG + uint64_t meta_esize = zfs_refcount_count( + &arc_anon->arcs_esize[ARC_BUFC_METADATA]); + uint64_t data_esize = + zfs_refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); + dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " + "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", + arc_tempreserve >> 10, meta_esize >> 10, + data_esize >> 10, reserve >> 10, arc_c >> 10); +#endif + DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle); + return (SET_ERROR(ERESTART)); + } + atomic_add_64(&arc_tempreserve, reserve); + return (0); +} + +static void +arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, + kstat_named_t *evict_data, kstat_named_t *evict_metadata) +{ + size->value.ui64 = zfs_refcount_count(&state->arcs_size); + evict_data->value.ui64 = + zfs_refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); + evict_metadata->value.ui64 = + zfs_refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); +} + +static int +arc_kstat_update(kstat_t *ksp, int rw) +{ + arc_stats_t *as = ksp->ks_data; + + if (rw == KSTAT_WRITE) { + return (SET_ERROR(EACCES)); + } else { + arc_kstat_update_state(arc_anon, + &as->arcstat_anon_size, + &as->arcstat_anon_evictable_data, + &as->arcstat_anon_evictable_metadata); + arc_kstat_update_state(arc_mru, + &as->arcstat_mru_size, + &as->arcstat_mru_evictable_data, + &as->arcstat_mru_evictable_metadata); + arc_kstat_update_state(arc_mru_ghost, + &as->arcstat_mru_ghost_size, + &as->arcstat_mru_ghost_evictable_data, + &as->arcstat_mru_ghost_evictable_metadata); + arc_kstat_update_state(arc_mfu, + &as->arcstat_mfu_size, + &as->arcstat_mfu_evictable_data, + &as->arcstat_mfu_evictable_metadata); + arc_kstat_update_state(arc_mfu_ghost, + &as->arcstat_mfu_ghost_size, + &as->arcstat_mfu_ghost_evictable_data, + &as->arcstat_mfu_ghost_evictable_metadata); + + ARCSTAT(arcstat_size) = aggsum_value(&arc_size); + ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used); + ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size); + ARCSTAT(arcstat_metadata_size) = + aggsum_value(&astat_metadata_size); + ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size); + ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size); + ARCSTAT(arcstat_dbuf_size) = aggsum_value(&astat_dbuf_size); +#if defined(COMPAT_FREEBSD11) + ARCSTAT(arcstat_other_size) = aggsum_value(&astat_bonus_size) + + aggsum_value(&astat_dnode_size) + + aggsum_value(&astat_dbuf_size); +#endif + ARCSTAT(arcstat_dnode_size) = aggsum_value(&astat_dnode_size); + ARCSTAT(arcstat_bonus_size) = aggsum_value(&astat_bonus_size); + ARCSTAT(arcstat_abd_chunk_waste_size) = + aggsum_value(&astat_abd_chunk_waste_size); + + as->arcstat_memory_all_bytes.value.ui64 = + arc_all_memory(); + as->arcstat_memory_free_bytes.value.ui64 = + arc_free_memory(); + as->arcstat_memory_available_bytes.value.i64 = + arc_available_memory(); + } + + return (0); +} + +/* + * This function *must* return indices evenly distributed between all + * sublists of the multilist. This is needed due to how the ARC eviction + * code is laid out; arc_evict_state() assumes ARC buffers are evenly + * distributed between all sublists and uses this assumption when + * deciding which sublist to evict from and how much to evict from it. + */ +static unsigned int +arc_state_multilist_index_func(multilist_t *ml, void *obj) +{ + arc_buf_hdr_t *hdr = obj; + + /* + * We rely on b_dva to generate evenly distributed index + * numbers using buf_hash below. So, as an added precaution, + * let's make sure we never add empty buffers to the arc lists. + */ + ASSERT(!HDR_EMPTY(hdr)); + + /* + * The assumption here, is the hash value for a given + * arc_buf_hdr_t will remain constant throughout its lifetime + * (i.e. its b_spa, b_dva, and b_birth fields don't change). + * Thus, we don't need to store the header's sublist index + * on insertion, as this index can be recalculated on removal. + * + * Also, the low order bits of the hash value are thought to be + * distributed evenly. Otherwise, in the case that the multilist + * has a power of two number of sublists, each sublists' usage + * would not be evenly distributed. + */ + return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % + multilist_get_num_sublists(ml)); +} + +#define WARN_IF_TUNING_IGNORED(tuning, value, do_warn) do { \ + if ((do_warn) && (tuning) && ((tuning) != (value))) { \ + cmn_err(CE_WARN, \ + "ignoring tunable %s (using %llu instead)", \ + (#tuning), (value)); \ + } \ +} while (0) + +/* + * Called during module initialization and periodically thereafter to + * apply reasonable changes to the exposed performance tunings. Can also be + * called explicitly by param_set_arc_*() functions when ARC tunables are + * updated manually. Non-zero zfs_* values which differ from the currently set + * values will be applied. + */ +void +arc_tuning_update(boolean_t verbose) +{ + uint64_t allmem = arc_all_memory(); + unsigned long limit; + + /* Valid range: 32M - <arc_c_max> */ + if ((zfs_arc_min) && (zfs_arc_min != arc_c_min) && + (zfs_arc_min >= 2ULL << SPA_MAXBLOCKSHIFT) && + (zfs_arc_min <= arc_c_max)) { + arc_c_min = zfs_arc_min; + arc_c = MAX(arc_c, arc_c_min); + } + WARN_IF_TUNING_IGNORED(zfs_arc_min, arc_c_min, verbose); + + /* Valid range: 64M - <all physical memory> */ + if ((zfs_arc_max) && (zfs_arc_max != arc_c_max) && + (zfs_arc_max >= 64 << 20) && (zfs_arc_max < allmem) && + (zfs_arc_max > arc_c_min)) { + arc_c_max = zfs_arc_max; + arc_c = MIN(arc_c, arc_c_max); + arc_p = (arc_c >> 1); + if (arc_meta_limit > arc_c_max) + arc_meta_limit = arc_c_max; + if (arc_dnode_size_limit > arc_meta_limit) + arc_dnode_size_limit = arc_meta_limit; + } + WARN_IF_TUNING_IGNORED(zfs_arc_max, arc_c_max, verbose); + + /* Valid range: 16M - <arc_c_max> */ + if ((zfs_arc_meta_min) && (zfs_arc_meta_min != arc_meta_min) && + (zfs_arc_meta_min >= 1ULL << SPA_MAXBLOCKSHIFT) && + (zfs_arc_meta_min <= arc_c_max)) { + arc_meta_min = zfs_arc_meta_min; + if (arc_meta_limit < arc_meta_min) + arc_meta_limit = arc_meta_min; + if (arc_dnode_size_limit < arc_meta_min) + arc_dnode_size_limit = arc_meta_min; + } + WARN_IF_TUNING_IGNORED(zfs_arc_meta_min, arc_meta_min, verbose); + + /* Valid range: <arc_meta_min> - <arc_c_max> */ + limit = zfs_arc_meta_limit ? zfs_arc_meta_limit : + MIN(zfs_arc_meta_limit_percent, 100) * arc_c_max / 100; + if ((limit != arc_meta_limit) && + (limit >= arc_meta_min) && + (limit <= arc_c_max)) + arc_meta_limit = limit; + WARN_IF_TUNING_IGNORED(zfs_arc_meta_limit, arc_meta_limit, verbose); + + /* Valid range: <arc_meta_min> - <arc_meta_limit> */ + limit = zfs_arc_dnode_limit ? zfs_arc_dnode_limit : + MIN(zfs_arc_dnode_limit_percent, 100) * arc_meta_limit / 100; + if ((limit != arc_dnode_size_limit) && + (limit >= arc_meta_min) && + (limit <= arc_meta_limit)) + arc_dnode_size_limit = limit; + WARN_IF_TUNING_IGNORED(zfs_arc_dnode_limit, arc_dnode_size_limit, + verbose); + + /* Valid range: 1 - N */ + if (zfs_arc_grow_retry) + arc_grow_retry = zfs_arc_grow_retry; + + /* Valid range: 1 - N */ + if (zfs_arc_shrink_shift) { + arc_shrink_shift = zfs_arc_shrink_shift; + arc_no_grow_shift = MIN(arc_no_grow_shift, arc_shrink_shift -1); + } + + /* Valid range: 1 - N */ + if (zfs_arc_p_min_shift) + arc_p_min_shift = zfs_arc_p_min_shift; + + /* Valid range: 1 - N ms */ + if (zfs_arc_min_prefetch_ms) + arc_min_prefetch_ms = zfs_arc_min_prefetch_ms; + + /* Valid range: 1 - N ms */ + if (zfs_arc_min_prescient_prefetch_ms) { + arc_min_prescient_prefetch_ms = + zfs_arc_min_prescient_prefetch_ms; + } + + /* Valid range: 0 - 100 */ + if ((zfs_arc_lotsfree_percent >= 0) && + (zfs_arc_lotsfree_percent <= 100)) + arc_lotsfree_percent = zfs_arc_lotsfree_percent; + WARN_IF_TUNING_IGNORED(zfs_arc_lotsfree_percent, arc_lotsfree_percent, + verbose); + + /* Valid range: 0 - <all physical memory> */ + if ((zfs_arc_sys_free) && (zfs_arc_sys_free != arc_sys_free)) + arc_sys_free = MIN(MAX(zfs_arc_sys_free, 0), allmem); + WARN_IF_TUNING_IGNORED(zfs_arc_sys_free, arc_sys_free, verbose); +} + +static void +arc_state_init(void) +{ + arc_anon = &ARC_anon; + arc_mru = &ARC_mru; + arc_mru_ghost = &ARC_mru_ghost; + arc_mfu = &ARC_mfu; + arc_mfu_ghost = &ARC_mfu_ghost; + arc_l2c_only = &ARC_l2c_only; + + arc_mru->arcs_list[ARC_BUFC_METADATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_mru->arcs_list[ARC_BUFC_DATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_mru_ghost->arcs_list[ARC_BUFC_DATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_mfu->arcs_list[ARC_BUFC_METADATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_mfu->arcs_list[ARC_BUFC_DATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_l2c_only->arcs_list[ARC_BUFC_METADATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + arc_l2c_only->arcs_list[ARC_BUFC_DATA] = + multilist_create(sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), + arc_state_multilist_index_func); + + zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); + + zfs_refcount_create(&arc_anon->arcs_size); + zfs_refcount_create(&arc_mru->arcs_size); + zfs_refcount_create(&arc_mru_ghost->arcs_size); + zfs_refcount_create(&arc_mfu->arcs_size); + zfs_refcount_create(&arc_mfu_ghost->arcs_size); + zfs_refcount_create(&arc_l2c_only->arcs_size); + + aggsum_init(&arc_meta_used, 0); + aggsum_init(&arc_size, 0); + aggsum_init(&astat_data_size, 0); + aggsum_init(&astat_metadata_size, 0); + aggsum_init(&astat_hdr_size, 0); + aggsum_init(&astat_l2_hdr_size, 0); + aggsum_init(&astat_bonus_size, 0); + aggsum_init(&astat_dnode_size, 0); + aggsum_init(&astat_dbuf_size, 0); + aggsum_init(&astat_abd_chunk_waste_size, 0); + + arc_anon->arcs_state = ARC_STATE_ANON; + arc_mru->arcs_state = ARC_STATE_MRU; + arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST; + arc_mfu->arcs_state = ARC_STATE_MFU; + arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST; + arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY; +} + +static void +arc_state_fini(void) +{ + zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); + zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); + zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); + + zfs_refcount_destroy(&arc_anon->arcs_size); + zfs_refcount_destroy(&arc_mru->arcs_size); + zfs_refcount_destroy(&arc_mru_ghost->arcs_size); + zfs_refcount_destroy(&arc_mfu->arcs_size); + zfs_refcount_destroy(&arc_mfu_ghost->arcs_size); + zfs_refcount_destroy(&arc_l2c_only->arcs_size); + + multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]); + multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); + multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]); + multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); + multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]); + multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); + multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]); + multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); + multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]); + multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_DATA]); + + aggsum_fini(&arc_meta_used); + aggsum_fini(&arc_size); + aggsum_fini(&astat_data_size); + aggsum_fini(&astat_metadata_size); + aggsum_fini(&astat_hdr_size); + aggsum_fini(&astat_l2_hdr_size); + aggsum_fini(&astat_bonus_size); + aggsum_fini(&astat_dnode_size); + aggsum_fini(&astat_dbuf_size); + aggsum_fini(&astat_abd_chunk_waste_size); +} + +uint64_t +arc_target_bytes(void) +{ + return (arc_c); +} + +void +arc_init(void) +{ + uint64_t percent, allmem = arc_all_memory(); + mutex_init(&arc_evict_lock, NULL, MUTEX_DEFAULT, NULL); + list_create(&arc_evict_waiters, sizeof (arc_evict_waiter_t), + offsetof(arc_evict_waiter_t, aew_node)); + + arc_min_prefetch_ms = 1000; + arc_min_prescient_prefetch_ms = 6000; + +#if defined(_KERNEL) + arc_lowmem_init(); +#endif + + /* Set min cache to 1/32 of all memory, or 32MB, whichever is more. */ + arc_c_min = MAX(allmem / 32, 2ULL << SPA_MAXBLOCKSHIFT); + + /* How to set default max varies by platform. */ + arc_c_max = arc_default_max(arc_c_min, allmem); + +#ifndef _KERNEL + /* + * In userland, there's only the memory pressure that we artificially + * create (see arc_available_memory()). Don't let arc_c get too + * small, because it can cause transactions to be larger than + * arc_c, causing arc_tempreserve_space() to fail. + */ + arc_c_min = MAX(arc_c_max / 2, 2ULL << SPA_MAXBLOCKSHIFT); +#endif + + arc_c = arc_c_min; + arc_p = (arc_c >> 1); + + /* Set min to 1/2 of arc_c_min */ + arc_meta_min = 1ULL << SPA_MAXBLOCKSHIFT; + /* Initialize maximum observed usage to zero */ + arc_meta_max = 0; + /* + * Set arc_meta_limit to a percent of arc_c_max with a floor of + * arc_meta_min, and a ceiling of arc_c_max. + */ + percent = MIN(zfs_arc_meta_limit_percent, 100); + arc_meta_limit = MAX(arc_meta_min, (percent * arc_c_max) / 100); + percent = MIN(zfs_arc_dnode_limit_percent, 100); + arc_dnode_size_limit = (percent * arc_meta_limit) / 100; + + /* Apply user specified tunings */ + arc_tuning_update(B_TRUE); + + /* if kmem_flags are set, lets try to use less memory */ + if (kmem_debugging()) + arc_c = arc_c / 2; + if (arc_c < arc_c_min) + arc_c = arc_c_min; + + arc_state_init(); + + buf_init(); + + list_create(&arc_prune_list, sizeof (arc_prune_t), + offsetof(arc_prune_t, p_node)); + mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL); + + arc_prune_taskq = taskq_create("arc_prune", boot_ncpus, defclsyspri, + boot_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC); + + arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, + sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); + + if (arc_ksp != NULL) { + arc_ksp->ks_data = &arc_stats; + arc_ksp->ks_update = arc_kstat_update; + kstat_install(arc_ksp); + } + + arc_evict_zthr = zthr_create_timer("arc_evict", + arc_evict_cb_check, arc_evict_cb, NULL, SEC2NSEC(1)); + arc_reap_zthr = zthr_create_timer("arc_reap", + arc_reap_cb_check, arc_reap_cb, NULL, SEC2NSEC(1)); + + arc_warm = B_FALSE; + + /* + * Calculate maximum amount of dirty data per pool. + * + * If it has been set by a module parameter, take that. + * Otherwise, use a percentage of physical memory defined by + * zfs_dirty_data_max_percent (default 10%) with a cap at + * zfs_dirty_data_max_max (default 4G or 25% of physical memory). + */ +#ifdef __LP64__ + if (zfs_dirty_data_max_max == 0) + zfs_dirty_data_max_max = MIN(4ULL * 1024 * 1024 * 1024, + allmem * zfs_dirty_data_max_max_percent / 100); +#else + if (zfs_dirty_data_max_max == 0) + zfs_dirty_data_max_max = MIN(1ULL * 1024 * 1024 * 1024, + allmem * zfs_dirty_data_max_max_percent / 100); +#endif + + if (zfs_dirty_data_max == 0) { + zfs_dirty_data_max = allmem * + zfs_dirty_data_max_percent / 100; + zfs_dirty_data_max = MIN(zfs_dirty_data_max, + zfs_dirty_data_max_max); + } +} + +void +arc_fini(void) +{ + arc_prune_t *p; + +#ifdef _KERNEL + arc_lowmem_fini(); +#endif /* _KERNEL */ + + /* Use B_TRUE to ensure *all* buffers are evicted */ + arc_flush(NULL, B_TRUE); + + if (arc_ksp != NULL) { + kstat_delete(arc_ksp); + arc_ksp = NULL; + } + + taskq_wait(arc_prune_taskq); + taskq_destroy(arc_prune_taskq); + + mutex_enter(&arc_prune_mtx); + while ((p = list_head(&arc_prune_list)) != NULL) { + list_remove(&arc_prune_list, p); + zfs_refcount_remove(&p->p_refcnt, &arc_prune_list); + zfs_refcount_destroy(&p->p_refcnt); + kmem_free(p, sizeof (*p)); + } + mutex_exit(&arc_prune_mtx); + + list_destroy(&arc_prune_list); + mutex_destroy(&arc_prune_mtx); + + (void) zthr_cancel(arc_evict_zthr); + (void) zthr_cancel(arc_reap_zthr); + + mutex_destroy(&arc_evict_lock); + list_destroy(&arc_evict_waiters); + + /* + * Free any buffers that were tagged for destruction. This needs + * to occur before arc_state_fini() runs and destroys the aggsum + * values which are updated when freeing scatter ABDs. + */ + l2arc_do_free_on_write(); + + /* + * buf_fini() must proceed arc_state_fini() because buf_fin() may + * trigger the release of kmem magazines, which can callback to + * arc_space_return() which accesses aggsums freed in act_state_fini(). + */ + buf_fini(); + arc_state_fini(); + + /* + * We destroy the zthrs after all the ARC state has been + * torn down to avoid the case of them receiving any + * wakeup() signals after they are destroyed. + */ + zthr_destroy(arc_evict_zthr); + zthr_destroy(arc_reap_zthr); + + ASSERT0(arc_loaned_bytes); +} + +/* + * Level 2 ARC + * + * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. + * It uses dedicated storage devices to hold cached data, which are populated + * using large infrequent writes. The main role of this cache is to boost + * the performance of random read workloads. The intended L2ARC devices + * include short-stroked disks, solid state disks, and other media with + * substantially faster read latency than disk. + * + * +-----------------------+ + * | ARC | + * +-----------------------+ + * | ^ ^ + * | | | + * l2arc_feed_thread() arc_read() + * | | | + * | l2arc read | + * V | | + * +---------------+ | + * | L2ARC | | + * +---------------+ | + * | ^ | + * l2arc_write() | | + * | | | + * V | | + * +-------+ +-------+ + * | vdev | | vdev | + * | cache | | cache | + * +-------+ +-------+ + * +=========+ .-----. + * : L2ARC : |-_____-| + * : devices : | Disks | + * +=========+ `-_____-' + * + * Read requests are satisfied from the following sources, in order: + * + * 1) ARC + * 2) vdev cache of L2ARC devices + * 3) L2ARC devices + * 4) vdev cache of disks + * 5) disks + * + * Some L2ARC device types exhibit extremely slow write performance. + * To accommodate for this there are some significant differences between + * the L2ARC and traditional cache design: + * + * 1. There is no eviction path from the ARC to the L2ARC. Evictions from + * the ARC behave as usual, freeing buffers and placing headers on ghost + * lists. The ARC does not send buffers to the L2ARC during eviction as + * this would add inflated write latencies for all ARC memory pressure. + * + * 2. The L2ARC attempts to cache data from the ARC before it is evicted. + * It does this by periodically scanning buffers from the eviction-end of + * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are + * not already there. It scans until a headroom of buffers is satisfied, + * which itself is a buffer for ARC eviction. If a compressible buffer is + * found during scanning and selected for writing to an L2ARC device, we + * temporarily boost scanning headroom during the next scan cycle to make + * sure we adapt to compression effects (which might significantly reduce + * the data volume we write to L2ARC). The thread that does this is + * l2arc_feed_thread(), illustrated below; example sizes are included to + * provide a better sense of ratio than this diagram: + * + * head --> tail + * +---------------------+----------+ + * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC + * +---------------------+----------+ | o L2ARC eligible + * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer + * +---------------------+----------+ | + * 15.9 Gbytes ^ 32 Mbytes | + * headroom | + * l2arc_feed_thread() + * | + * l2arc write hand <--[oooo]--' + * | 8 Mbyte + * | write max + * V + * +==============================+ + * L2ARC dev |####|#|###|###| |####| ... | + * +==============================+ + * 32 Gbytes + * + * 3. If an ARC buffer is copied to the L2ARC but then hit instead of + * evicted, then the L2ARC has cached a buffer much sooner than it probably + * needed to, potentially wasting L2ARC device bandwidth and storage. It is + * safe to say that this is an uncommon case, since buffers at the end of + * the ARC lists have moved there due to inactivity. + * + * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, + * then the L2ARC simply misses copying some buffers. This serves as a + * pressure valve to prevent heavy read workloads from both stalling the ARC + * with waits and clogging the L2ARC with writes. This also helps prevent + * the potential for the L2ARC to churn if it attempts to cache content too + * quickly, such as during backups of the entire pool. + * + * 5. After system boot and before the ARC has filled main memory, there are + * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru + * lists can remain mostly static. Instead of searching from tail of these + * lists as pictured, the l2arc_feed_thread() will search from the list heads + * for eligible buffers, greatly increasing its chance of finding them. + * + * The L2ARC device write speed is also boosted during this time so that + * the L2ARC warms up faster. Since there have been no ARC evictions yet, + * there are no L2ARC reads, and no fear of degrading read performance + * through increased writes. + * + * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that + * the vdev queue can aggregate them into larger and fewer writes. Each + * device is written to in a rotor fashion, sweeping writes through + * available space then repeating. + * + * 7. The L2ARC does not store dirty content. It never needs to flush + * write buffers back to disk based storage. + * + * 8. If an ARC buffer is written (and dirtied) which also exists in the + * L2ARC, the now stale L2ARC buffer is immediately dropped. + * + * The performance of the L2ARC can be tweaked by a number of tunables, which + * may be necessary for different workloads: + * + * l2arc_write_max max write bytes per interval + * l2arc_write_boost extra write bytes during device warmup + * l2arc_noprefetch skip caching prefetched buffers + * l2arc_headroom number of max device writes to precache + * l2arc_headroom_boost when we find compressed buffers during ARC + * scanning, we multiply headroom by this + * percentage factor for the next scan cycle, + * since more compressed buffers are likely to + * be present + * l2arc_feed_secs seconds between L2ARC writing + * + * Tunables may be removed or added as future performance improvements are + * integrated, and also may become zpool properties. + * + * There are three key functions that control how the L2ARC warms up: + * + * l2arc_write_eligible() check if a buffer is eligible to cache + * l2arc_write_size() calculate how much to write + * l2arc_write_interval() calculate sleep delay between writes + * + * These three functions determine what to write, how much, and how quickly + * to send writes. + * + * L2ARC persistence: + * + * When writing buffers to L2ARC, we periodically add some metadata to + * make sure we can pick them up after reboot, thus dramatically reducing + * the impact that any downtime has on the performance of storage systems + * with large caches. + * + * The implementation works fairly simply by integrating the following two + * modifications: + * + * *) When writing to the L2ARC, we occasionally write a "l2arc log block", + * which is an additional piece of metadata which describes what's been + * written. This allows us to rebuild the arc_buf_hdr_t structures of the + * main ARC buffers. There are 2 linked-lists of log blocks headed by + * dh_start_lbps[2]. We alternate which chain we append to, so they are + * time-wise and offset-wise interleaved, but that is an optimization rather + * than for correctness. The log block also includes a pointer to the + * previous block in its chain. + * + * *) We reserve SPA_MINBLOCKSIZE of space at the start of each L2ARC device + * for our header bookkeeping purposes. This contains a device header, + * which contains our top-level reference structures. We update it each + * time we write a new log block, so that we're able to locate it in the + * L2ARC device. If this write results in an inconsistent device header + * (e.g. due to power failure), we detect this by verifying the header's + * checksum and simply fail to reconstruct the L2ARC after reboot. + * + * Implementation diagram: + * + * +=== L2ARC device (not to scale) ======================================+ + * | ___two newest log block pointers__.__________ | + * | / \dh_start_lbps[1] | + * | / \ \dh_start_lbps[0]| + * |.___/__. V V | + * ||L2 dev|....|lb |bufs |lb |bufs |lb |bufs |lb |bufs |lb |---(empty)---| + * || hdr| ^ /^ /^ / / | + * |+------+ ...--\-------/ \-----/--\------/ / | + * | \--------------/ \--------------/ | + * +======================================================================+ + * + * As can be seen on the diagram, rather than using a simple linked list, + * we use a pair of linked lists with alternating elements. This is a + * performance enhancement due to the fact that we only find out the + * address of the next log block access once the current block has been + * completely read in. Obviously, this hurts performance, because we'd be + * keeping the device's I/O queue at only a 1 operation deep, thus + * incurring a large amount of I/O round-trip latency. Having two lists + * allows us to fetch two log blocks ahead of where we are currently + * rebuilding L2ARC buffers. + * + * On-device data structures: + * + * L2ARC device header: l2arc_dev_hdr_phys_t + * L2ARC log block: l2arc_log_blk_phys_t + * + * L2ARC reconstruction: + * + * When writing data, we simply write in the standard rotary fashion, + * evicting buffers as we go and simply writing new data over them (writing + * a new log block every now and then). This obviously means that once we + * loop around the end of the device, we will start cutting into an already + * committed log block (and its referenced data buffers), like so: + * + * current write head__ __old tail + * \ / + * V V + * <--|bufs |lb |bufs |lb | |bufs |lb |bufs |lb |--> + * ^ ^^^^^^^^^___________________________________ + * | \ + * <<nextwrite>> may overwrite this blk and/or its bufs --' + * + * When importing the pool, we detect this situation and use it to stop + * our scanning process (see l2arc_rebuild). + * + * There is one significant caveat to consider when rebuilding ARC contents + * from an L2ARC device: what about invalidated buffers? Given the above + * construction, we cannot update blocks which we've already written to amend + * them to remove buffers which were invalidated. Thus, during reconstruction, + * we might be populating the cache with buffers for data that's not on the + * main pool anymore, or may have been overwritten! + * + * As it turns out, this isn't a problem. Every arc_read request includes + * both the DVA and, crucially, the birth TXG of the BP the caller is + * looking for. So even if the cache were populated by completely rotten + * blocks for data that had been long deleted and/or overwritten, we'll + * never actually return bad data from the cache, since the DVA with the + * birth TXG uniquely identify a block in space and time - once created, + * a block is immutable on disk. The worst thing we have done is wasted + * some time and memory at l2arc rebuild to reconstruct outdated ARC + * entries that will get dropped from the l2arc as it is being updated + * with new blocks. + * + * L2ARC buffers that have been evicted by l2arc_evict() ahead of the write + * hand are not restored. This is done by saving the offset (in bytes) + * l2arc_evict() has evicted to in the L2ARC device header and taking it + * into account when restoring buffers. + */ + +static boolean_t +l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) +{ + /* + * A buffer is *not* eligible for the L2ARC if it: + * 1. belongs to a different spa. + * 2. is already cached on the L2ARC. + * 3. has an I/O in progress (it may be an incomplete read). + * 4. is flagged not eligible (zfs property). + */ + if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || + HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr)) + return (B_FALSE); + + return (B_TRUE); +} + +static uint64_t +l2arc_write_size(l2arc_dev_t *dev) +{ + uint64_t size, dev_size, tsize; + + /* + * Make sure our globals have meaningful values in case the user + * altered them. + */ + size = l2arc_write_max; + if (size == 0) { + cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " + "be greater than zero, resetting it to the default (%d)", + L2ARC_WRITE_SIZE); + size = l2arc_write_max = L2ARC_WRITE_SIZE; + } + + if (arc_warm == B_FALSE) + size += l2arc_write_boost; + + /* + * Make sure the write size does not exceed the size of the cache + * device. This is important in l2arc_evict(), otherwise infinite + * iteration can occur. + */ + dev_size = dev->l2ad_end - dev->l2ad_start; + tsize = size + l2arc_log_blk_overhead(size, dev); + if (dev->l2ad_vdev->vdev_has_trim && l2arc_trim_ahead > 0) + tsize += MAX(64 * 1024 * 1024, + (tsize * l2arc_trim_ahead) / 100); + + if (tsize >= dev_size) { + cmn_err(CE_NOTE, "l2arc_write_max or l2arc_write_boost " + "plus the overhead of log blocks (persistent L2ARC, " + "%llu bytes) exceeds the size of the cache device " + "(guid %llu), resetting them to the default (%d)", + l2arc_log_blk_overhead(size, dev), + dev->l2ad_vdev->vdev_guid, L2ARC_WRITE_SIZE); + size = l2arc_write_max = l2arc_write_boost = L2ARC_WRITE_SIZE; + + if (arc_warm == B_FALSE) + size += l2arc_write_boost; + } + + return (size); + +} + +static clock_t +l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) +{ + clock_t interval, next, now; + + /* + * If the ARC lists are busy, increase our write rate; if the + * lists are stale, idle back. This is achieved by checking + * how much we previously wrote - if it was more than half of + * what we wanted, schedule the next write much sooner. + */ + if (l2arc_feed_again && wrote > (wanted / 2)) + interval = (hz * l2arc_feed_min_ms) / 1000; + else + interval = hz * l2arc_feed_secs; + + now = ddi_get_lbolt(); + next = MAX(now, MIN(now + interval, began + interval)); + + return (next); +} + +/* + * Cycle through L2ARC devices. This is how L2ARC load balances. + * If a device is returned, this also returns holding the spa config lock. + */ +static l2arc_dev_t * +l2arc_dev_get_next(void) +{ + l2arc_dev_t *first, *next = NULL; + + /* + * Lock out the removal of spas (spa_namespace_lock), then removal + * of cache devices (l2arc_dev_mtx). Once a device has been selected, + * both locks will be dropped and a spa config lock held instead. + */ + mutex_enter(&spa_namespace_lock); + mutex_enter(&l2arc_dev_mtx); + + /* if there are no vdevs, there is nothing to do */ + if (l2arc_ndev == 0) + goto out; + + first = NULL; + next = l2arc_dev_last; + do { + /* loop around the list looking for a non-faulted vdev */ + if (next == NULL) { + next = list_head(l2arc_dev_list); + } else { + next = list_next(l2arc_dev_list, next); + if (next == NULL) + next = list_head(l2arc_dev_list); + } + + /* if we have come back to the start, bail out */ + if (first == NULL) + first = next; + else if (next == first) + break; + + } while (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild || + next->l2ad_trim_all); + + /* if we were unable to find any usable vdevs, return NULL */ + if (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild || + next->l2ad_trim_all) + next = NULL; + + l2arc_dev_last = next; + +out: + mutex_exit(&l2arc_dev_mtx); + + /* + * Grab the config lock to prevent the 'next' device from being + * removed while we are writing to it. + */ + if (next != NULL) + spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); + mutex_exit(&spa_namespace_lock); + + return (next); +} + +/* + * Free buffers that were tagged for destruction. + */ +static void +l2arc_do_free_on_write(void) +{ + list_t *buflist; + l2arc_data_free_t *df, *df_prev; + + mutex_enter(&l2arc_free_on_write_mtx); + buflist = l2arc_free_on_write; + + for (df = list_tail(buflist); df; df = df_prev) { + df_prev = list_prev(buflist, df); + ASSERT3P(df->l2df_abd, !=, NULL); + abd_free(df->l2df_abd); + list_remove(buflist, df); + kmem_free(df, sizeof (l2arc_data_free_t)); + } + + mutex_exit(&l2arc_free_on_write_mtx); +} + +/* + * A write to a cache device has completed. Update all headers to allow + * reads from these buffers to begin. + */ +static void +l2arc_write_done(zio_t *zio) +{ + l2arc_write_callback_t *cb; + l2arc_lb_abd_buf_t *abd_buf; + l2arc_lb_ptr_buf_t *lb_ptr_buf; + l2arc_dev_t *dev; + l2arc_dev_hdr_phys_t *l2dhdr; + list_t *buflist; + arc_buf_hdr_t *head, *hdr, *hdr_prev; + kmutex_t *hash_lock; + int64_t bytes_dropped = 0; + + cb = zio->io_private; + ASSERT3P(cb, !=, NULL); + dev = cb->l2wcb_dev; + l2dhdr = dev->l2ad_dev_hdr; + ASSERT3P(dev, !=, NULL); + head = cb->l2wcb_head; + ASSERT3P(head, !=, NULL); + buflist = &dev->l2ad_buflist; + ASSERT3P(buflist, !=, NULL); + DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, + l2arc_write_callback_t *, cb); + + if (zio->io_error != 0) + ARCSTAT_BUMP(arcstat_l2_writes_error); + + /* + * All writes completed, or an error was hit. + */ +top: + mutex_enter(&dev->l2ad_mtx); + for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { + hdr_prev = list_prev(buflist, hdr); + + hash_lock = HDR_LOCK(hdr); + + /* + * We cannot use mutex_enter or else we can deadlock + * with l2arc_write_buffers (due to swapping the order + * the hash lock and l2ad_mtx are taken). + */ + if (!mutex_tryenter(hash_lock)) { + /* + * Missed the hash lock. We must retry so we + * don't leave the ARC_FLAG_L2_WRITING bit set. + */ + ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); + + /* + * We don't want to rescan the headers we've + * already marked as having been written out, so + * we reinsert the head node so we can pick up + * where we left off. + */ + list_remove(buflist, head); + list_insert_after(buflist, hdr, head); + + mutex_exit(&dev->l2ad_mtx); + + /* + * We wait for the hash lock to become available + * to try and prevent busy waiting, and increase + * the chance we'll be able to acquire the lock + * the next time around. + */ + mutex_enter(hash_lock); + mutex_exit(hash_lock); + goto top; + } + + /* + * We could not have been moved into the arc_l2c_only + * state while in-flight due to our ARC_FLAG_L2_WRITING + * bit being set. Let's just ensure that's being enforced. + */ + ASSERT(HDR_HAS_L1HDR(hdr)); + + /* + * Skipped - drop L2ARC entry and mark the header as no + * longer L2 eligibile. + */ + if (zio->io_error != 0) { + /* + * Error - drop L2ARC entry. + */ + list_remove(buflist, hdr); + arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); + + uint64_t psize = HDR_GET_PSIZE(hdr); + ARCSTAT_INCR(arcstat_l2_psize, -psize); + ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); + + bytes_dropped += + vdev_psize_to_asize(dev->l2ad_vdev, psize); + (void) zfs_refcount_remove_many(&dev->l2ad_alloc, + arc_hdr_size(hdr), hdr); + } + + /* + * Allow ARC to begin reads and ghost list evictions to + * this L2ARC entry. + */ + arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); + + mutex_exit(hash_lock); + } + + /* + * Free the allocated abd buffers for writing the log blocks. + * If the zio failed reclaim the allocated space and remove the + * pointers to these log blocks from the log block pointer list + * of the L2ARC device. + */ + while ((abd_buf = list_remove_tail(&cb->l2wcb_abd_list)) != NULL) { + abd_free(abd_buf->abd); + zio_buf_free(abd_buf, sizeof (*abd_buf)); + if (zio->io_error != 0) { + lb_ptr_buf = list_remove_head(&dev->l2ad_lbptr_list); + /* + * L2BLK_GET_PSIZE returns aligned size for log + * blocks. + */ + uint64_t asize = + L2BLK_GET_PSIZE((lb_ptr_buf->lb_ptr)->lbp_prop); + bytes_dropped += asize; + ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize); + ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count); + zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize, + lb_ptr_buf); + zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf); + kmem_free(lb_ptr_buf->lb_ptr, + sizeof (l2arc_log_blkptr_t)); + kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t)); + } + } + list_destroy(&cb->l2wcb_abd_list); + + if (zio->io_error != 0) { + /* + * Restore the lbps array in the header to its previous state. + * If the list of log block pointers is empty, zero out the + * log block pointers in the device header. + */ + lb_ptr_buf = list_head(&dev->l2ad_lbptr_list); + for (int i = 0; i < 2; i++) { + if (lb_ptr_buf == NULL) { + /* + * If the list is empty zero out the device + * header. Otherwise zero out the second log + * block pointer in the header. + */ + if (i == 0) { + bzero(l2dhdr, dev->l2ad_dev_hdr_asize); + } else { + bzero(&l2dhdr->dh_start_lbps[i], + sizeof (l2arc_log_blkptr_t)); + } + break; + } + bcopy(lb_ptr_buf->lb_ptr, &l2dhdr->dh_start_lbps[i], + sizeof (l2arc_log_blkptr_t)); + lb_ptr_buf = list_next(&dev->l2ad_lbptr_list, + lb_ptr_buf); + } + } + + atomic_inc_64(&l2arc_writes_done); + list_remove(buflist, head); + ASSERT(!HDR_HAS_L1HDR(head)); + kmem_cache_free(hdr_l2only_cache, head); + mutex_exit(&dev->l2ad_mtx); + + ASSERT(dev->l2ad_vdev != NULL); + vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); + + l2arc_do_free_on_write(); + + kmem_free(cb, sizeof (l2arc_write_callback_t)); +} + +static int +l2arc_untransform(zio_t *zio, l2arc_read_callback_t *cb) +{ + int ret; + spa_t *spa = zio->io_spa; + arc_buf_hdr_t *hdr = cb->l2rcb_hdr; + blkptr_t *bp = zio->io_bp; + uint8_t salt[ZIO_DATA_SALT_LEN]; + uint8_t iv[ZIO_DATA_IV_LEN]; + uint8_t mac[ZIO_DATA_MAC_LEN]; + boolean_t no_crypt = B_FALSE; + + /* + * ZIL data is never be written to the L2ARC, so we don't need + * special handling for its unique MAC storage. + */ + ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG); + ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + + /* + * If the data was encrypted, decrypt it now. Note that + * we must check the bp here and not the hdr, since the + * hdr does not have its encryption parameters updated + * until arc_read_done(). + */ + if (BP_IS_ENCRYPTED(bp)) { + abd_t *eabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr, + B_TRUE); + + zio_crypt_decode_params_bp(bp, salt, iv); + zio_crypt_decode_mac_bp(bp, mac); + + ret = spa_do_crypt_abd(B_FALSE, spa, &cb->l2rcb_zb, + BP_GET_TYPE(bp), BP_GET_DEDUP(bp), BP_SHOULD_BYTESWAP(bp), + salt, iv, mac, HDR_GET_PSIZE(hdr), eabd, + hdr->b_l1hdr.b_pabd, &no_crypt); + if (ret != 0) { + arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr); + goto error; + } + + /* + * If we actually performed decryption, replace b_pabd + * with the decrypted data. Otherwise we can just throw + * our decryption buffer away. + */ + if (!no_crypt) { + arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, + arc_hdr_size(hdr), hdr); + hdr->b_l1hdr.b_pabd = eabd; + zio->io_abd = eabd; + } else { + arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr); + } + } + + /* + * If the L2ARC block was compressed, but ARC compression + * is disabled we decompress the data into a new buffer and + * replace the existing data. + */ + if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && + !HDR_COMPRESSION_ENABLED(hdr)) { + abd_t *cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr, + B_TRUE); + void *tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr)); + + ret = zio_decompress_data(HDR_GET_COMPRESS(hdr), + hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr), + HDR_GET_LSIZE(hdr), &hdr->b_complevel); + if (ret != 0) { + abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr)); + arc_free_data_abd(hdr, cabd, arc_hdr_size(hdr), hdr); + goto error; + } + + abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr)); + arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, + arc_hdr_size(hdr), hdr); + hdr->b_l1hdr.b_pabd = cabd; + zio->io_abd = cabd; + zio->io_size = HDR_GET_LSIZE(hdr); + } + + return (0); + +error: + return (ret); +} + + +/* + * A read to a cache device completed. Validate buffer contents before + * handing over to the regular ARC routines. + */ +static void +l2arc_read_done(zio_t *zio) +{ + int tfm_error = 0; + l2arc_read_callback_t *cb = zio->io_private; + arc_buf_hdr_t *hdr; + kmutex_t *hash_lock; + boolean_t valid_cksum; + boolean_t using_rdata = (BP_IS_ENCRYPTED(&cb->l2rcb_bp) && + (cb->l2rcb_flags & ZIO_FLAG_RAW_ENCRYPT)); + + ASSERT3P(zio->io_vd, !=, NULL); + ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); + + spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); + + ASSERT3P(cb, !=, NULL); + hdr = cb->l2rcb_hdr; + ASSERT3P(hdr, !=, NULL); + + hash_lock = HDR_LOCK(hdr); + mutex_enter(hash_lock); + ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); + + /* + * If the data was read into a temporary buffer, + * move it and free the buffer. + */ + if (cb->l2rcb_abd != NULL) { + ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); + if (zio->io_error == 0) { + if (using_rdata) { + abd_copy(hdr->b_crypt_hdr.b_rabd, + cb->l2rcb_abd, arc_hdr_size(hdr)); + } else { + abd_copy(hdr->b_l1hdr.b_pabd, + cb->l2rcb_abd, arc_hdr_size(hdr)); + } + } + + /* + * The following must be done regardless of whether + * there was an error: + * - free the temporary buffer + * - point zio to the real ARC buffer + * - set zio size accordingly + * These are required because zio is either re-used for + * an I/O of the block in the case of the error + * or the zio is passed to arc_read_done() and it + * needs real data. + */ + abd_free(cb->l2rcb_abd); + zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); + + if (using_rdata) { + ASSERT(HDR_HAS_RABD(hdr)); + zio->io_abd = zio->io_orig_abd = + hdr->b_crypt_hdr.b_rabd; + } else { + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd; + } + } + + ASSERT3P(zio->io_abd, !=, NULL); + + /* + * Check this survived the L2ARC journey. + */ + ASSERT(zio->io_abd == hdr->b_l1hdr.b_pabd || + (HDR_HAS_RABD(hdr) && zio->io_abd == hdr->b_crypt_hdr.b_rabd)); + zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ + zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ + zio->io_prop.zp_complevel = hdr->b_complevel; + + valid_cksum = arc_cksum_is_equal(hdr, zio); + + /* + * b_rabd will always match the data as it exists on disk if it is + * being used. Therefore if we are reading into b_rabd we do not + * attempt to untransform the data. + */ + if (valid_cksum && !using_rdata) + tfm_error = l2arc_untransform(zio, cb); + + if (valid_cksum && tfm_error == 0 && zio->io_error == 0 && + !HDR_L2_EVICTED(hdr)) { + mutex_exit(hash_lock); + zio->io_private = hdr; + arc_read_done(zio); + } else { + /* + * Buffer didn't survive caching. Increment stats and + * reissue to the original storage device. + */ + if (zio->io_error != 0) { + ARCSTAT_BUMP(arcstat_l2_io_error); + } else { + zio->io_error = SET_ERROR(EIO); + } + if (!valid_cksum || tfm_error != 0) + ARCSTAT_BUMP(arcstat_l2_cksum_bad); + + /* + * If there's no waiter, issue an async i/o to the primary + * storage now. If there *is* a waiter, the caller must + * issue the i/o in a context where it's OK to block. + */ + if (zio->io_waiter == NULL) { + zio_t *pio = zio_unique_parent(zio); + void *abd = (using_rdata) ? + hdr->b_crypt_hdr.b_rabd : hdr->b_l1hdr.b_pabd; + + ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); + + zio = zio_read(pio, zio->io_spa, zio->io_bp, + abd, zio->io_size, arc_read_done, + hdr, zio->io_priority, cb->l2rcb_flags, + &cb->l2rcb_zb); + + /* + * Original ZIO will be freed, so we need to update + * ARC header with the new ZIO pointer to be used + * by zio_change_priority() in arc_read(). + */ + for (struct arc_callback *acb = hdr->b_l1hdr.b_acb; + acb != NULL; acb = acb->acb_next) + acb->acb_zio_head = zio; + + mutex_exit(hash_lock); + zio_nowait(zio); + } else { + mutex_exit(hash_lock); + } + } + + kmem_free(cb, sizeof (l2arc_read_callback_t)); +} + +/* + * This is the list priority from which the L2ARC will search for pages to + * cache. This is used within loops (0..3) to cycle through lists in the + * desired order. This order can have a significant effect on cache + * performance. + * + * Currently the metadata lists are hit first, MFU then MRU, followed by + * the data lists. This function returns a locked list, and also returns + * the lock pointer. + */ +static multilist_sublist_t * +l2arc_sublist_lock(int list_num) +{ + multilist_t *ml = NULL; + unsigned int idx; + + ASSERT(list_num >= 0 && list_num < L2ARC_FEED_TYPES); + + switch (list_num) { + case 0: + ml = arc_mfu->arcs_list[ARC_BUFC_METADATA]; + break; + case 1: + ml = arc_mru->arcs_list[ARC_BUFC_METADATA]; + break; + case 2: + ml = arc_mfu->arcs_list[ARC_BUFC_DATA]; + break; + case 3: + ml = arc_mru->arcs_list[ARC_BUFC_DATA]; + break; + default: + return (NULL); + } + + /* + * Return a randomly-selected sublist. This is acceptable + * because the caller feeds only a little bit of data for each + * call (8MB). Subsequent calls will result in different + * sublists being selected. + */ + idx = multilist_get_random_index(ml); + return (multilist_sublist_lock(ml, idx)); +} + +/* + * Calculates the maximum overhead of L2ARC metadata log blocks for a given + * L2ARC write size. l2arc_evict and l2arc_write_size need to include this + * overhead in processing to make sure there is enough headroom available + * when writing buffers. + */ +static inline uint64_t +l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev) +{ + if (dev->l2ad_log_entries == 0) { + return (0); + } else { + uint64_t log_entries = write_sz >> SPA_MINBLOCKSHIFT; + + uint64_t log_blocks = (log_entries + + dev->l2ad_log_entries - 1) / + dev->l2ad_log_entries; + + return (vdev_psize_to_asize(dev->l2ad_vdev, + sizeof (l2arc_log_blk_phys_t)) * log_blocks); + } +} + +/* + * Evict buffers from the device write hand to the distance specified in + * bytes. This distance may span populated buffers, it may span nothing. + * This is clearing a region on the L2ARC device ready for writing. + * If the 'all' boolean is set, every buffer is evicted. + */ +static void +l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) +{ + list_t *buflist; + arc_buf_hdr_t *hdr, *hdr_prev; + kmutex_t *hash_lock; + uint64_t taddr; + l2arc_lb_ptr_buf_t *lb_ptr_buf, *lb_ptr_buf_prev; + vdev_t *vd = dev->l2ad_vdev; + boolean_t rerun; + + buflist = &dev->l2ad_buflist; + + /* + * We need to add in the worst case scenario of log block overhead. + */ + distance += l2arc_log_blk_overhead(distance, dev); + if (vd->vdev_has_trim && l2arc_trim_ahead > 0) { + /* + * Trim ahead of the write size 64MB or (l2arc_trim_ahead/100) + * times the write size, whichever is greater. + */ + distance += MAX(64 * 1024 * 1024, + (distance * l2arc_trim_ahead) / 100); + } + +top: + rerun = B_FALSE; + if (dev->l2ad_hand >= (dev->l2ad_end - distance)) { + /* + * When there is no space to accommodate upcoming writes, + * evict to the end. Then bump the write and evict hands + * to the start and iterate. This iteration does not + * happen indefinitely as we make sure in + * l2arc_write_size() that when the write hand is reset, + * the write size does not exceed the end of the device. + */ + rerun = B_TRUE; + taddr = dev->l2ad_end; + } else { + taddr = dev->l2ad_hand + distance; + } + DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, + uint64_t, taddr, boolean_t, all); + + if (!all) { + /* + * This check has to be placed after deciding whether to + * iterate (rerun). + */ + if (dev->l2ad_first) { + /* + * This is the first sweep through the device. There is + * nothing to evict. We have already trimmmed the + * whole device. + */ + goto out; + } else { + /* + * Trim the space to be evicted. + */ + if (vd->vdev_has_trim && dev->l2ad_evict < taddr && + l2arc_trim_ahead > 0) { + /* + * We have to drop the spa_config lock because + * vdev_trim_range() will acquire it. + * l2ad_evict already accounts for the label + * size. To prevent vdev_trim_ranges() from + * adding it again, we subtract it from + * l2ad_evict. + */ + spa_config_exit(dev->l2ad_spa, SCL_L2ARC, dev); + vdev_trim_simple(vd, + dev->l2ad_evict - VDEV_LABEL_START_SIZE, + taddr - dev->l2ad_evict); + spa_config_enter(dev->l2ad_spa, SCL_L2ARC, dev, + RW_READER); + } + + /* + * When rebuilding L2ARC we retrieve the evict hand + * from the header of the device. Of note, l2arc_evict() + * does not actually delete buffers from the cache + * device, but trimming may do so depending on the + * hardware implementation. Thus keeping track of the + * evict hand is useful. + */ + dev->l2ad_evict = MAX(dev->l2ad_evict, taddr); + } + } + +retry: + mutex_enter(&dev->l2ad_mtx); + /* + * We have to account for evicted log blocks. Run vdev_space_update() + * on log blocks whose offset (in bytes) is before the evicted offset + * (in bytes) by searching in the list of pointers to log blocks + * present in the L2ARC device. + */ + for (lb_ptr_buf = list_tail(&dev->l2ad_lbptr_list); lb_ptr_buf; + lb_ptr_buf = lb_ptr_buf_prev) { + + lb_ptr_buf_prev = list_prev(&dev->l2ad_lbptr_list, lb_ptr_buf); + + /* L2BLK_GET_PSIZE returns aligned size for log blocks */ + uint64_t asize = L2BLK_GET_PSIZE( + (lb_ptr_buf->lb_ptr)->lbp_prop); + + /* + * We don't worry about log blocks left behind (ie + * lbp_payload_start < l2ad_hand) because l2arc_write_buffers() + * will never write more than l2arc_evict() evicts. + */ + if (!all && l2arc_log_blkptr_valid(dev, lb_ptr_buf->lb_ptr)) { + break; + } else { + vdev_space_update(vd, -asize, 0, 0); + ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize); + ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count); + zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize, + lb_ptr_buf); + zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf); + list_remove(&dev->l2ad_lbptr_list, lb_ptr_buf); + kmem_free(lb_ptr_buf->lb_ptr, + sizeof (l2arc_log_blkptr_t)); + kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t)); + } + } + + for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { + hdr_prev = list_prev(buflist, hdr); + + ASSERT(!HDR_EMPTY(hdr)); + hash_lock = HDR_LOCK(hdr); + + /* + * We cannot use mutex_enter or else we can deadlock + * with l2arc_write_buffers (due to swapping the order + * the hash lock and l2ad_mtx are taken). + */ + if (!mutex_tryenter(hash_lock)) { + /* + * Missed the hash lock. Retry. + */ + ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); + mutex_exit(&dev->l2ad_mtx); + mutex_enter(hash_lock); + mutex_exit(hash_lock); + goto retry; + } + + /* + * A header can't be on this list if it doesn't have L2 header. + */ + ASSERT(HDR_HAS_L2HDR(hdr)); + + /* Ensure this header has finished being written. */ + ASSERT(!HDR_L2_WRITING(hdr)); + ASSERT(!HDR_L2_WRITE_HEAD(hdr)); + + if (!all && (hdr->b_l2hdr.b_daddr >= dev->l2ad_evict || + hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { + /* + * We've evicted to the target address, + * or the end of the device. + */ + mutex_exit(hash_lock); + break; + } + + if (!HDR_HAS_L1HDR(hdr)) { + ASSERT(!HDR_L2_READING(hdr)); + /* + * This doesn't exist in the ARC. Destroy. + * arc_hdr_destroy() will call list_remove() + * and decrement arcstat_l2_lsize. + */ + arc_change_state(arc_anon, hdr, hash_lock); + arc_hdr_destroy(hdr); + } else { + ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); + ARCSTAT_BUMP(arcstat_l2_evict_l1cached); + /* + * Invalidate issued or about to be issued + * reads, since we may be about to write + * over this location. + */ + if (HDR_L2_READING(hdr)) { + ARCSTAT_BUMP(arcstat_l2_evict_reading); + arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); + } + + arc_hdr_l2hdr_destroy(hdr); + } + mutex_exit(hash_lock); + } + mutex_exit(&dev->l2ad_mtx); + +out: + /* + * We need to check if we evict all buffers, otherwise we may iterate + * unnecessarily. + */ + if (!all && rerun) { + /* + * Bump device hand to the device start if it is approaching the + * end. l2arc_evict() has already evicted ahead for this case. + */ + dev->l2ad_hand = dev->l2ad_start; + dev->l2ad_evict = dev->l2ad_start; + dev->l2ad_first = B_FALSE; + goto top; + } + + ASSERT3U(dev->l2ad_hand + distance, <, dev->l2ad_end); + if (!dev->l2ad_first) + ASSERT3U(dev->l2ad_hand, <, dev->l2ad_evict); +} + +/* + * Handle any abd transforms that might be required for writing to the L2ARC. + * If successful, this function will always return an abd with the data + * transformed as it is on disk in a new abd of asize bytes. + */ +static int +l2arc_apply_transforms(spa_t *spa, arc_buf_hdr_t *hdr, uint64_t asize, + abd_t **abd_out) +{ + int ret; + void *tmp = NULL; + abd_t *cabd = NULL, *eabd = NULL, *to_write = hdr->b_l1hdr.b_pabd; + enum zio_compress compress = HDR_GET_COMPRESS(hdr); + uint64_t psize = HDR_GET_PSIZE(hdr); + uint64_t size = arc_hdr_size(hdr); + boolean_t ismd = HDR_ISTYPE_METADATA(hdr); + boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS); + dsl_crypto_key_t *dck = NULL; + uint8_t mac[ZIO_DATA_MAC_LEN] = { 0 }; + boolean_t no_crypt = B_FALSE; + + ASSERT((HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && + !HDR_COMPRESSION_ENABLED(hdr)) || + HDR_ENCRYPTED(hdr) || HDR_SHARED_DATA(hdr) || psize != asize); + ASSERT3U(psize, <=, asize); + + /* + * If this data simply needs its own buffer, we simply allocate it + * and copy the data. This may be done to eliminate a dependency on a + * shared buffer or to reallocate the buffer to match asize. + */ + if (HDR_HAS_RABD(hdr) && asize != psize) { + ASSERT3U(asize, >=, psize); + to_write = abd_alloc_for_io(asize, ismd); + abd_copy(to_write, hdr->b_crypt_hdr.b_rabd, psize); + if (psize != asize) + abd_zero_off(to_write, psize, asize - psize); + goto out; + } + + if ((compress == ZIO_COMPRESS_OFF || HDR_COMPRESSION_ENABLED(hdr)) && + !HDR_ENCRYPTED(hdr)) { + ASSERT3U(size, ==, psize); + to_write = abd_alloc_for_io(asize, ismd); + abd_copy(to_write, hdr->b_l1hdr.b_pabd, size); + if (size != asize) + abd_zero_off(to_write, size, asize - size); + goto out; + } + + if (compress != ZIO_COMPRESS_OFF && !HDR_COMPRESSION_ENABLED(hdr)) { + cabd = abd_alloc_for_io(asize, ismd); + tmp = abd_borrow_buf(cabd, asize); + + psize = zio_compress_data(compress, to_write, tmp, size, + hdr->b_complevel); + + if (psize >= size) { + abd_return_buf(cabd, tmp, asize); + HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); + to_write = cabd; + abd_copy(to_write, hdr->b_l1hdr.b_pabd, size); + if (size != asize) + abd_zero_off(to_write, size, asize - size); + goto encrypt; + } + ASSERT3U(psize, <=, HDR_GET_PSIZE(hdr)); + if (psize < asize) + bzero((char *)tmp + psize, asize - psize); + psize = HDR_GET_PSIZE(hdr); + abd_return_buf_copy(cabd, tmp, asize); + to_write = cabd; + } + +encrypt: + if (HDR_ENCRYPTED(hdr)) { + eabd = abd_alloc_for_io(asize, ismd); + + /* + * If the dataset was disowned before the buffer + * made it to this point, the key to re-encrypt + * it won't be available. In this case we simply + * won't write the buffer to the L2ARC. + */ + ret = spa_keystore_lookup_key(spa, hdr->b_crypt_hdr.b_dsobj, + FTAG, &dck); + if (ret != 0) + goto error; + + ret = zio_do_crypt_abd(B_TRUE, &dck->dck_key, + hdr->b_crypt_hdr.b_ot, bswap, hdr->b_crypt_hdr.b_salt, + hdr->b_crypt_hdr.b_iv, mac, psize, to_write, eabd, + &no_crypt); + if (ret != 0) + goto error; + + if (no_crypt) + abd_copy(eabd, to_write, psize); + + if (psize != asize) + abd_zero_off(eabd, psize, asize - psize); + + /* assert that the MAC we got here matches the one we saved */ + ASSERT0(bcmp(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN)); + spa_keystore_dsl_key_rele(spa, dck, FTAG); + + if (to_write == cabd) + abd_free(cabd); + + to_write = eabd; + } + +out: + ASSERT3P(to_write, !=, hdr->b_l1hdr.b_pabd); + *abd_out = to_write; + return (0); + +error: + if (dck != NULL) + spa_keystore_dsl_key_rele(spa, dck, FTAG); + if (cabd != NULL) + abd_free(cabd); + if (eabd != NULL) + abd_free(eabd); + + *abd_out = NULL; + return (ret); +} + +static void +l2arc_blk_fetch_done(zio_t *zio) +{ + l2arc_read_callback_t *cb; + + cb = zio->io_private; + if (cb->l2rcb_abd != NULL) + abd_put(cb->l2rcb_abd); + kmem_free(cb, sizeof (l2arc_read_callback_t)); +} + +/* + * Find and write ARC buffers to the L2ARC device. + * + * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid + * for reading until they have completed writing. + * The headroom_boost is an in-out parameter used to maintain headroom boost + * state between calls to this function. + * + * Returns the number of bytes actually written (which may be smaller than + * the delta by which the device hand has changed due to alignment and the + * writing of log blocks). + */ +static uint64_t +l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) +{ + arc_buf_hdr_t *hdr, *hdr_prev, *head; + uint64_t write_asize, write_psize, write_lsize, headroom; + boolean_t full; + l2arc_write_callback_t *cb = NULL; + zio_t *pio, *wzio; + uint64_t guid = spa_load_guid(spa); + + ASSERT3P(dev->l2ad_vdev, !=, NULL); + + pio = NULL; + write_lsize = write_asize = write_psize = 0; + full = B_FALSE; + head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); + arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); + + /* + * Copy buffers for L2ARC writing. + */ + for (int try = 0; try < L2ARC_FEED_TYPES; try++) { + multilist_sublist_t *mls = l2arc_sublist_lock(try); + uint64_t passed_sz = 0; + + VERIFY3P(mls, !=, NULL); + + /* + * L2ARC fast warmup. + * + * Until the ARC is warm and starts to evict, read from the + * head of the ARC lists rather than the tail. + */ + if (arc_warm == B_FALSE) + hdr = multilist_sublist_head(mls); + else + hdr = multilist_sublist_tail(mls); + + headroom = target_sz * l2arc_headroom; + if (zfs_compressed_arc_enabled) + headroom = (headroom * l2arc_headroom_boost) / 100; + + for (; hdr; hdr = hdr_prev) { + kmutex_t *hash_lock; + abd_t *to_write = NULL; + + if (arc_warm == B_FALSE) + hdr_prev = multilist_sublist_next(mls, hdr); + else + hdr_prev = multilist_sublist_prev(mls, hdr); + + hash_lock = HDR_LOCK(hdr); + if (!mutex_tryenter(hash_lock)) { + /* + * Skip this buffer rather than waiting. + */ + continue; + } + + passed_sz += HDR_GET_LSIZE(hdr); + if (l2arc_headroom != 0 && passed_sz > headroom) { + /* + * Searched too far. + */ + mutex_exit(hash_lock); + break; + } + + if (!l2arc_write_eligible(guid, hdr)) { + mutex_exit(hash_lock); + continue; + } + + /* + * We rely on the L1 portion of the header below, so + * it's invalid for this header to have been evicted out + * of the ghost cache, prior to being written out. The + * ARC_FLAG_L2_WRITING bit ensures this won't happen. + */ + ASSERT(HDR_HAS_L1HDR(hdr)); + + ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); + ASSERT3U(arc_hdr_size(hdr), >, 0); + ASSERT(hdr->b_l1hdr.b_pabd != NULL || + HDR_HAS_RABD(hdr)); + uint64_t psize = HDR_GET_PSIZE(hdr); + uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, + psize); + + if ((write_asize + asize) > target_sz) { + full = B_TRUE; + mutex_exit(hash_lock); + break; + } + + /* + * We rely on the L1 portion of the header below, so + * it's invalid for this header to have been evicted out + * of the ghost cache, prior to being written out. The + * ARC_FLAG_L2_WRITING bit ensures this won't happen. + */ + arc_hdr_set_flags(hdr, ARC_FLAG_L2_WRITING); + ASSERT(HDR_HAS_L1HDR(hdr)); + + ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); + ASSERT(hdr->b_l1hdr.b_pabd != NULL || + HDR_HAS_RABD(hdr)); + ASSERT3U(arc_hdr_size(hdr), >, 0); + + /* + * If this header has b_rabd, we can use this since it + * must always match the data exactly as it exists on + * disk. Otherwise, the L2ARC can normally use the + * hdr's data, but if we're sharing data between the + * hdr and one of its bufs, L2ARC needs its own copy of + * the data so that the ZIO below can't race with the + * buf consumer. To ensure that this copy will be + * available for the lifetime of the ZIO and be cleaned + * up afterwards, we add it to the l2arc_free_on_write + * queue. If we need to apply any transforms to the + * data (compression, encryption) we will also need the + * extra buffer. + */ + if (HDR_HAS_RABD(hdr) && psize == asize) { + to_write = hdr->b_crypt_hdr.b_rabd; + } else if ((HDR_COMPRESSION_ENABLED(hdr) || + HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) && + !HDR_ENCRYPTED(hdr) && !HDR_SHARED_DATA(hdr) && + psize == asize) { + to_write = hdr->b_l1hdr.b_pabd; + } else { + int ret; + arc_buf_contents_t type = arc_buf_type(hdr); + + ret = l2arc_apply_transforms(spa, hdr, asize, + &to_write); + if (ret != 0) { + arc_hdr_clear_flags(hdr, + ARC_FLAG_L2_WRITING); + mutex_exit(hash_lock); + continue; + } + + l2arc_free_abd_on_write(to_write, asize, type); + } + + if (pio == NULL) { + /* + * Insert a dummy header on the buflist so + * l2arc_write_done() can find where the + * write buffers begin without searching. + */ + mutex_enter(&dev->l2ad_mtx); + list_insert_head(&dev->l2ad_buflist, head); + mutex_exit(&dev->l2ad_mtx); + + cb = kmem_alloc( + sizeof (l2arc_write_callback_t), KM_SLEEP); + cb->l2wcb_dev = dev; + cb->l2wcb_head = head; + /* + * Create a list to save allocated abd buffers + * for l2arc_log_blk_commit(). + */ + list_create(&cb->l2wcb_abd_list, + sizeof (l2arc_lb_abd_buf_t), + offsetof(l2arc_lb_abd_buf_t, node)); + pio = zio_root(spa, l2arc_write_done, cb, + ZIO_FLAG_CANFAIL); + } + + hdr->b_l2hdr.b_dev = dev; + hdr->b_l2hdr.b_hits = 0; + + hdr->b_l2hdr.b_daddr = dev->l2ad_hand; + arc_hdr_set_flags(hdr, ARC_FLAG_HAS_L2HDR); + + mutex_enter(&dev->l2ad_mtx); + list_insert_head(&dev->l2ad_buflist, hdr); + mutex_exit(&dev->l2ad_mtx); + + (void) zfs_refcount_add_many(&dev->l2ad_alloc, + arc_hdr_size(hdr), hdr); + + wzio = zio_write_phys(pio, dev->l2ad_vdev, + hdr->b_l2hdr.b_daddr, asize, to_write, + ZIO_CHECKSUM_OFF, NULL, hdr, + ZIO_PRIORITY_ASYNC_WRITE, + ZIO_FLAG_CANFAIL, B_FALSE); + + write_lsize += HDR_GET_LSIZE(hdr); + DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, + zio_t *, wzio); + + write_psize += psize; + write_asize += asize; + dev->l2ad_hand += asize; + vdev_space_update(dev->l2ad_vdev, asize, 0, 0); + + mutex_exit(hash_lock); + + /* + * Append buf info to current log and commit if full. + * arcstat_l2_{size,asize} kstats are updated + * internally. + */ + if (l2arc_log_blk_insert(dev, hdr)) + l2arc_log_blk_commit(dev, pio, cb); + + zio_nowait(wzio); + } + + multilist_sublist_unlock(mls); + + if (full == B_TRUE) + break; + } + + /* No buffers selected for writing? */ + if (pio == NULL) { + ASSERT0(write_lsize); + ASSERT(!HDR_HAS_L1HDR(head)); + kmem_cache_free(hdr_l2only_cache, head); + + /* + * Although we did not write any buffers l2ad_evict may + * have advanced. + */ + l2arc_dev_hdr_update(dev); + + return (0); + } + + if (!dev->l2ad_first) + ASSERT3U(dev->l2ad_hand, <=, dev->l2ad_evict); + + ASSERT3U(write_asize, <=, target_sz); + ARCSTAT_BUMP(arcstat_l2_writes_sent); + ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize); + ARCSTAT_INCR(arcstat_l2_lsize, write_lsize); + ARCSTAT_INCR(arcstat_l2_psize, write_psize); + + dev->l2ad_writing = B_TRUE; + (void) zio_wait(pio); + dev->l2ad_writing = B_FALSE; + + /* + * Update the device header after the zio completes as + * l2arc_write_done() may have updated the memory holding the log block + * pointers in the device header. + */ + l2arc_dev_hdr_update(dev); + + return (write_asize); +} + +/* + * This thread feeds the L2ARC at regular intervals. This is the beating + * heart of the L2ARC. + */ +/* ARGSUSED */ +static void +l2arc_feed_thread(void *unused) +{ + callb_cpr_t cpr; + l2arc_dev_t *dev; + spa_t *spa; + uint64_t size, wrote; + clock_t begin, next = ddi_get_lbolt(); + fstrans_cookie_t cookie; + + CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); + + mutex_enter(&l2arc_feed_thr_lock); + + cookie = spl_fstrans_mark(); + while (l2arc_thread_exit == 0) { + CALLB_CPR_SAFE_BEGIN(&cpr); + (void) cv_timedwait_sig(&l2arc_feed_thr_cv, + &l2arc_feed_thr_lock, next); + CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); + next = ddi_get_lbolt() + hz; + + /* + * Quick check for L2ARC devices. + */ + mutex_enter(&l2arc_dev_mtx); + if (l2arc_ndev == 0) { + mutex_exit(&l2arc_dev_mtx); + continue; + } + mutex_exit(&l2arc_dev_mtx); + begin = ddi_get_lbolt(); + + /* + * This selects the next l2arc device to write to, and in + * doing so the next spa to feed from: dev->l2ad_spa. This + * will return NULL if there are now no l2arc devices or if + * they are all faulted. + * + * If a device is returned, its spa's config lock is also + * held to prevent device removal. l2arc_dev_get_next() + * will grab and release l2arc_dev_mtx. + */ + if ((dev = l2arc_dev_get_next()) == NULL) + continue; + + spa = dev->l2ad_spa; + ASSERT3P(spa, !=, NULL); + + /* + * If the pool is read-only then force the feed thread to + * sleep a little longer. + */ + if (!spa_writeable(spa)) { + next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; + spa_config_exit(spa, SCL_L2ARC, dev); + continue; + } + + /* + * Avoid contributing to memory pressure. + */ + if (arc_reclaim_needed()) { + ARCSTAT_BUMP(arcstat_l2_abort_lowmem); + spa_config_exit(spa, SCL_L2ARC, dev); + continue; + } + + ARCSTAT_BUMP(arcstat_l2_feeds); + + size = l2arc_write_size(dev); + + /* + * Evict L2ARC buffers that will be overwritten. + */ + l2arc_evict(dev, size, B_FALSE); + + /* + * Write ARC buffers. + */ + wrote = l2arc_write_buffers(spa, dev, size); + + /* + * Calculate interval between writes. + */ + next = l2arc_write_interval(begin, size, wrote); + spa_config_exit(spa, SCL_L2ARC, dev); + } + spl_fstrans_unmark(cookie); + + l2arc_thread_exit = 0; + cv_broadcast(&l2arc_feed_thr_cv); + CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ + thread_exit(); +} + +boolean_t +l2arc_vdev_present(vdev_t *vd) +{ + return (l2arc_vdev_get(vd) != NULL); +} + +/* + * Returns the l2arc_dev_t associated with a particular vdev_t or NULL if + * the vdev_t isn't an L2ARC device. + */ +l2arc_dev_t * +l2arc_vdev_get(vdev_t *vd) +{ + l2arc_dev_t *dev; + + mutex_enter(&l2arc_dev_mtx); + for (dev = list_head(l2arc_dev_list); dev != NULL; + dev = list_next(l2arc_dev_list, dev)) { + if (dev->l2ad_vdev == vd) + break; + } + mutex_exit(&l2arc_dev_mtx); + + return (dev); +} + +/* + * Add a vdev for use by the L2ARC. By this point the spa has already + * validated the vdev and opened it. + */ +void +l2arc_add_vdev(spa_t *spa, vdev_t *vd) +{ + l2arc_dev_t *adddev; + uint64_t l2dhdr_asize; + + ASSERT(!l2arc_vdev_present(vd)); + + vdev_ashift_optimize(vd); + + /* + * Create a new l2arc device entry. + */ + adddev = vmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); + adddev->l2ad_spa = spa; + adddev->l2ad_vdev = vd; + /* leave extra size for an l2arc device header */ + l2dhdr_asize = adddev->l2ad_dev_hdr_asize = + MAX(sizeof (*adddev->l2ad_dev_hdr), 1 << vd->vdev_ashift); + adddev->l2ad_start = VDEV_LABEL_START_SIZE + l2dhdr_asize; + adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); + ASSERT3U(adddev->l2ad_start, <, adddev->l2ad_end); + adddev->l2ad_hand = adddev->l2ad_start; + adddev->l2ad_evict = adddev->l2ad_start; + adddev->l2ad_first = B_TRUE; + adddev->l2ad_writing = B_FALSE; + adddev->l2ad_trim_all = B_FALSE; + list_link_init(&adddev->l2ad_node); + adddev->l2ad_dev_hdr = kmem_zalloc(l2dhdr_asize, KM_SLEEP); + + mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); + /* + * This is a list of all ARC buffers that are still valid on the + * device. + */ + list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), + offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); + + /* + * This is a list of pointers to log blocks that are still present + * on the device. + */ + list_create(&adddev->l2ad_lbptr_list, sizeof (l2arc_lb_ptr_buf_t), + offsetof(l2arc_lb_ptr_buf_t, node)); + + vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); + zfs_refcount_create(&adddev->l2ad_alloc); + zfs_refcount_create(&adddev->l2ad_lb_asize); + zfs_refcount_create(&adddev->l2ad_lb_count); + + /* + * Add device to global list + */ + mutex_enter(&l2arc_dev_mtx); + list_insert_head(l2arc_dev_list, adddev); + atomic_inc_64(&l2arc_ndev); + mutex_exit(&l2arc_dev_mtx); + + /* + * Decide if vdev is eligible for L2ARC rebuild + */ + l2arc_rebuild_vdev(adddev->l2ad_vdev, B_FALSE); +} + +void +l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen) +{ + l2arc_dev_t *dev = NULL; + l2arc_dev_hdr_phys_t *l2dhdr; + uint64_t l2dhdr_asize; + spa_t *spa; + int err; + boolean_t l2dhdr_valid = B_TRUE; + + dev = l2arc_vdev_get(vd); + ASSERT3P(dev, !=, NULL); + spa = dev->l2ad_spa; + l2dhdr = dev->l2ad_dev_hdr; + l2dhdr_asize = dev->l2ad_dev_hdr_asize; + + /* + * The L2ARC has to hold at least the payload of one log block for + * them to be restored (persistent L2ARC). The payload of a log block + * depends on the amount of its log entries. We always write log blocks + * with 1022 entries. How many of them are committed or restored depends + * on the size of the L2ARC device. Thus the maximum payload of + * one log block is 1022 * SPA_MAXBLOCKSIZE = 16GB. If the L2ARC device + * is less than that, we reduce the amount of committed and restored + * log entries per block so as to enable persistence. + */ + if (dev->l2ad_end < l2arc_rebuild_blocks_min_l2size) { + dev->l2ad_log_entries = 0; + } else { + dev->l2ad_log_entries = MIN((dev->l2ad_end - + dev->l2ad_start) >> SPA_MAXBLOCKSHIFT, + L2ARC_LOG_BLK_MAX_ENTRIES); + } + + /* + * Read the device header, if an error is returned do not rebuild L2ARC. + */ + if ((err = l2arc_dev_hdr_read(dev)) != 0) + l2dhdr_valid = B_FALSE; + + if (l2dhdr_valid && dev->l2ad_log_entries > 0) { + /* + * If we are onlining a cache device (vdev_reopen) that was + * still present (l2arc_vdev_present()) and rebuild is enabled, + * we should evict all ARC buffers and pointers to log blocks + * and reclaim their space before restoring its contents to + * L2ARC. + */ + if (reopen) { + if (!l2arc_rebuild_enabled) { + return; + } else { + l2arc_evict(dev, 0, B_TRUE); + /* start a new log block */ + dev->l2ad_log_ent_idx = 0; + dev->l2ad_log_blk_payload_asize = 0; + dev->l2ad_log_blk_payload_start = 0; + } + } + /* + * Just mark the device as pending for a rebuild. We won't + * be starting a rebuild in line here as it would block pool + * import. Instead spa_load_impl will hand that off to an + * async task which will call l2arc_spa_rebuild_start. + */ + dev->l2ad_rebuild = B_TRUE; + } else if (spa_writeable(spa)) { + /* + * In this case TRIM the whole device if l2arc_trim_ahead > 0, + * otherwise create a new header. We zero out the memory holding + * the header to reset dh_start_lbps. If we TRIM the whole + * device the new header will be written by + * vdev_trim_l2arc_thread() at the end of the TRIM to update the + * trim_state in the header too. When reading the header, if + * trim_state is not VDEV_TRIM_COMPLETE and l2arc_trim_ahead > 0 + * we opt to TRIM the whole device again. + */ + if (l2arc_trim_ahead > 0) { + dev->l2ad_trim_all = B_TRUE; + } else { + bzero(l2dhdr, l2dhdr_asize); + l2arc_dev_hdr_update(dev); + } + } +} + +/* + * Remove a vdev from the L2ARC. + */ +void +l2arc_remove_vdev(vdev_t *vd) +{ + l2arc_dev_t *remdev = NULL; + + /* + * Find the device by vdev + */ + remdev = l2arc_vdev_get(vd); + ASSERT3P(remdev, !=, NULL); + + /* + * Cancel any ongoing or scheduled rebuild. + */ + mutex_enter(&l2arc_rebuild_thr_lock); + if (remdev->l2ad_rebuild_began == B_TRUE) { + remdev->l2ad_rebuild_cancel = B_TRUE; + while (remdev->l2ad_rebuild == B_TRUE) + cv_wait(&l2arc_rebuild_thr_cv, &l2arc_rebuild_thr_lock); + } + mutex_exit(&l2arc_rebuild_thr_lock); + + /* + * Remove device from global list + */ + mutex_enter(&l2arc_dev_mtx); + list_remove(l2arc_dev_list, remdev); + l2arc_dev_last = NULL; /* may have been invalidated */ + atomic_dec_64(&l2arc_ndev); + mutex_exit(&l2arc_dev_mtx); + + /* + * Clear all buflists and ARC references. L2ARC device flush. + */ + l2arc_evict(remdev, 0, B_TRUE); + list_destroy(&remdev->l2ad_buflist); + ASSERT(list_is_empty(&remdev->l2ad_lbptr_list)); + list_destroy(&remdev->l2ad_lbptr_list); + mutex_destroy(&remdev->l2ad_mtx); + zfs_refcount_destroy(&remdev->l2ad_alloc); + zfs_refcount_destroy(&remdev->l2ad_lb_asize); + zfs_refcount_destroy(&remdev->l2ad_lb_count); + kmem_free(remdev->l2ad_dev_hdr, remdev->l2ad_dev_hdr_asize); + vmem_free(remdev, sizeof (l2arc_dev_t)); +} + +void +l2arc_init(void) +{ + l2arc_thread_exit = 0; + l2arc_ndev = 0; + l2arc_writes_sent = 0; + l2arc_writes_done = 0; + + mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); + cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); + mutex_init(&l2arc_rebuild_thr_lock, NULL, MUTEX_DEFAULT, NULL); + cv_init(&l2arc_rebuild_thr_cv, NULL, CV_DEFAULT, NULL); + mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); + mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); + + l2arc_dev_list = &L2ARC_dev_list; + l2arc_free_on_write = &L2ARC_free_on_write; + list_create(l2arc_dev_list, sizeof (l2arc_dev_t), + offsetof(l2arc_dev_t, l2ad_node)); + list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), + offsetof(l2arc_data_free_t, l2df_list_node)); +} + +void +l2arc_fini(void) +{ + mutex_destroy(&l2arc_feed_thr_lock); + cv_destroy(&l2arc_feed_thr_cv); + mutex_destroy(&l2arc_rebuild_thr_lock); + cv_destroy(&l2arc_rebuild_thr_cv); + mutex_destroy(&l2arc_dev_mtx); + mutex_destroy(&l2arc_free_on_write_mtx); + + list_destroy(l2arc_dev_list); + list_destroy(l2arc_free_on_write); +} + +void +l2arc_start(void) +{ + if (!(spa_mode_global & SPA_MODE_WRITE)) + return; + + (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, + TS_RUN, defclsyspri); +} + +void +l2arc_stop(void) +{ + if (!(spa_mode_global & SPA_MODE_WRITE)) + return; + + mutex_enter(&l2arc_feed_thr_lock); + cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ + l2arc_thread_exit = 1; + while (l2arc_thread_exit != 0) + cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); + mutex_exit(&l2arc_feed_thr_lock); +} + +/* + * Punches out rebuild threads for the L2ARC devices in a spa. This should + * be called after pool import from the spa async thread, since starting + * these threads directly from spa_import() will make them part of the + * "zpool import" context and delay process exit (and thus pool import). + */ +void +l2arc_spa_rebuild_start(spa_t *spa) +{ + ASSERT(MUTEX_HELD(&spa_namespace_lock)); + + /* + * Locate the spa's l2arc devices and kick off rebuild threads. + */ + for (int i = 0; i < spa->spa_l2cache.sav_count; i++) { + l2arc_dev_t *dev = + l2arc_vdev_get(spa->spa_l2cache.sav_vdevs[i]); + if (dev == NULL) { + /* Don't attempt a rebuild if the vdev is UNAVAIL */ + continue; + } + mutex_enter(&l2arc_rebuild_thr_lock); + if (dev->l2ad_rebuild && !dev->l2ad_rebuild_cancel) { + dev->l2ad_rebuild_began = B_TRUE; + (void) thread_create(NULL, 0, l2arc_dev_rebuild_thread, + dev, 0, &p0, TS_RUN, minclsyspri); + } + mutex_exit(&l2arc_rebuild_thr_lock); + } +} + +/* + * Main entry point for L2ARC rebuilding. + */ +static void +l2arc_dev_rebuild_thread(void *arg) +{ + l2arc_dev_t *dev = arg; + + VERIFY(!dev->l2ad_rebuild_cancel); + VERIFY(dev->l2ad_rebuild); + (void) l2arc_rebuild(dev); + mutex_enter(&l2arc_rebuild_thr_lock); + dev->l2ad_rebuild_began = B_FALSE; + dev->l2ad_rebuild = B_FALSE; + mutex_exit(&l2arc_rebuild_thr_lock); + + thread_exit(); +} + +/* + * This function implements the actual L2ARC metadata rebuild. It: + * starts reading the log block chain and restores each block's contents + * to memory (reconstructing arc_buf_hdr_t's). + * + * Operation stops under any of the following conditions: + * + * 1) We reach the end of the log block chain. + * 2) We encounter *any* error condition (cksum errors, io errors) + */ +static int +l2arc_rebuild(l2arc_dev_t *dev) +{ + vdev_t *vd = dev->l2ad_vdev; + spa_t *spa = vd->vdev_spa; + int err = 0; + l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr; + l2arc_log_blk_phys_t *this_lb, *next_lb; + zio_t *this_io = NULL, *next_io = NULL; + l2arc_log_blkptr_t lbps[2]; + l2arc_lb_ptr_buf_t *lb_ptr_buf; + boolean_t lock_held; + + this_lb = vmem_zalloc(sizeof (*this_lb), KM_SLEEP); + next_lb = vmem_zalloc(sizeof (*next_lb), KM_SLEEP); + + /* + * We prevent device removal while issuing reads to the device, + * then during the rebuilding phases we drop this lock again so + * that a spa_unload or device remove can be initiated - this is + * safe, because the spa will signal us to stop before removing + * our device and wait for us to stop. + */ + spa_config_enter(spa, SCL_L2ARC, vd, RW_READER); + lock_held = B_TRUE; + + /* + * Retrieve the persistent L2ARC device state. + * L2BLK_GET_PSIZE returns aligned size for log blocks. + */ + dev->l2ad_evict = MAX(l2dhdr->dh_evict, dev->l2ad_start); + dev->l2ad_hand = MAX(l2dhdr->dh_start_lbps[0].lbp_daddr + + L2BLK_GET_PSIZE((&l2dhdr->dh_start_lbps[0])->lbp_prop), + dev->l2ad_start); + dev->l2ad_first = !!(l2dhdr->dh_flags & L2ARC_DEV_HDR_EVICT_FIRST); + + vd->vdev_trim_action_time = l2dhdr->dh_trim_action_time; + vd->vdev_trim_state = l2dhdr->dh_trim_state; + + /* + * In case the zfs module parameter l2arc_rebuild_enabled is false + * we do not start the rebuild process. + */ + if (!l2arc_rebuild_enabled) + goto out; + + /* Prepare the rebuild process */ + bcopy(l2dhdr->dh_start_lbps, lbps, sizeof (lbps)); + + /* Start the rebuild process */ + for (;;) { + if (!l2arc_log_blkptr_valid(dev, &lbps[0])) + break; + + if ((err = l2arc_log_blk_read(dev, &lbps[0], &lbps[1], + this_lb, next_lb, this_io, &next_io)) != 0) + goto out; + + /* + * Our memory pressure valve. If the system is running low + * on memory, rather than swamping memory with new ARC buf + * hdrs, we opt not to rebuild the L2ARC. At this point, + * however, we have already set up our L2ARC dev to chain in + * new metadata log blocks, so the user may choose to offline/ + * online the L2ARC dev at a later time (or re-import the pool) + * to reconstruct it (when there's less memory pressure). + */ + if (arc_reclaim_needed()) { + ARCSTAT_BUMP(arcstat_l2_rebuild_abort_lowmem); + cmn_err(CE_NOTE, "System running low on memory, " + "aborting L2ARC rebuild."); + err = SET_ERROR(ENOMEM); + goto out; + } + + spa_config_exit(spa, SCL_L2ARC, vd); + lock_held = B_FALSE; + + /* + * Now that we know that the next_lb checks out alright, we + * can start reconstruction from this log block. + * L2BLK_GET_PSIZE returns aligned size for log blocks. + */ + uint64_t asize = L2BLK_GET_PSIZE((&lbps[0])->lbp_prop); + l2arc_log_blk_restore(dev, this_lb, asize, lbps[0].lbp_daddr); + + /* + * log block restored, include its pointer in the list of + * pointers to log blocks present in the L2ARC device. + */ + lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP); + lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t), + KM_SLEEP); + bcopy(&lbps[0], lb_ptr_buf->lb_ptr, + sizeof (l2arc_log_blkptr_t)); + mutex_enter(&dev->l2ad_mtx); + list_insert_tail(&dev->l2ad_lbptr_list, lb_ptr_buf); + ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize); + ARCSTAT_BUMP(arcstat_l2_log_blk_count); + zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf); + zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf); + mutex_exit(&dev->l2ad_mtx); + vdev_space_update(vd, asize, 0, 0); + + /* + * Protection against loops of log blocks: + * + * l2ad_hand l2ad_evict + * V V + * l2ad_start |=======================================| l2ad_end + * -----|||----|||---|||----||| + * (3) (2) (1) (0) + * ---|||---|||----|||---||| + * (7) (6) (5) (4) + * + * In this situation the pointer of log block (4) passes + * l2arc_log_blkptr_valid() but the log block should not be + * restored as it is overwritten by the payload of log block + * (0). Only log blocks (0)-(3) should be restored. We check + * whether l2ad_evict lies in between the payload starting + * offset of the next log block (lbps[1].lbp_payload_start) + * and the payload starting offset of the present log block + * (lbps[0].lbp_payload_start). If true and this isn't the + * first pass, we are looping from the beginning and we should + * stop. + */ + if (l2arc_range_check_overlap(lbps[1].lbp_payload_start, + lbps[0].lbp_payload_start, dev->l2ad_evict) && + !dev->l2ad_first) + goto out; + + for (;;) { + mutex_enter(&l2arc_rebuild_thr_lock); + if (dev->l2ad_rebuild_cancel) { + dev->l2ad_rebuild = B_FALSE; + cv_signal(&l2arc_rebuild_thr_cv); + mutex_exit(&l2arc_rebuild_thr_lock); + err = SET_ERROR(ECANCELED); + goto out; + } + mutex_exit(&l2arc_rebuild_thr_lock); + if (spa_config_tryenter(spa, SCL_L2ARC, vd, + RW_READER)) { + lock_held = B_TRUE; + break; + } + /* + * L2ARC config lock held by somebody in writer, + * possibly due to them trying to remove us. They'll + * likely to want us to shut down, so after a little + * delay, we check l2ad_rebuild_cancel and retry + * the lock again. + */ + delay(1); + } + + /* + * Continue with the next log block. + */ + lbps[0] = lbps[1]; + lbps[1] = this_lb->lb_prev_lbp; + PTR_SWAP(this_lb, next_lb); + this_io = next_io; + next_io = NULL; + } + + if (this_io != NULL) + l2arc_log_blk_fetch_abort(this_io); +out: + if (next_io != NULL) + l2arc_log_blk_fetch_abort(next_io); + vmem_free(this_lb, sizeof (*this_lb)); + vmem_free(next_lb, sizeof (*next_lb)); + + if (!l2arc_rebuild_enabled) { + spa_history_log_internal(spa, "L2ARC rebuild", NULL, + "disabled"); + } else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) > 0) { + ARCSTAT_BUMP(arcstat_l2_rebuild_success); + spa_history_log_internal(spa, "L2ARC rebuild", NULL, + "successful, restored %llu blocks", + (u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count)); + } else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) == 0) { + /* + * No error but also nothing restored, meaning the lbps array + * in the device header points to invalid/non-present log + * blocks. Reset the header. + */ + spa_history_log_internal(spa, "L2ARC rebuild", NULL, + "no valid log blocks"); + bzero(l2dhdr, dev->l2ad_dev_hdr_asize); + l2arc_dev_hdr_update(dev); + } else if (err == ECANCELED) { + /* + * In case the rebuild was canceled do not log to spa history + * log as the pool may be in the process of being removed. + */ + zfs_dbgmsg("L2ARC rebuild aborted, restored %llu blocks", + zfs_refcount_count(&dev->l2ad_lb_count)); + } else if (err != 0) { + spa_history_log_internal(spa, "L2ARC rebuild", NULL, + "aborted, restored %llu blocks", + (u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count)); + } + + if (lock_held) + spa_config_exit(spa, SCL_L2ARC, vd); + + return (err); +} + +/* + * Attempts to read the device header on the provided L2ARC device and writes + * it to `hdr'. On success, this function returns 0, otherwise the appropriate + * error code is returned. + */ +static int +l2arc_dev_hdr_read(l2arc_dev_t *dev) +{ + int err; + uint64_t guid; + l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr; + const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize; + abd_t *abd; + + guid = spa_guid(dev->l2ad_vdev->vdev_spa); + + abd = abd_get_from_buf(l2dhdr, l2dhdr_asize); + + err = zio_wait(zio_read_phys(NULL, dev->l2ad_vdev, + VDEV_LABEL_START_SIZE, l2dhdr_asize, abd, + ZIO_CHECKSUM_LABEL, NULL, NULL, ZIO_PRIORITY_ASYNC_READ, + ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | + ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY | + ZIO_FLAG_SPECULATIVE, B_FALSE)); + + abd_put(abd); + + if (err != 0) { + ARCSTAT_BUMP(arcstat_l2_rebuild_abort_dh_errors); + zfs_dbgmsg("L2ARC IO error (%d) while reading device header, " + "vdev guid: %llu", err, dev->l2ad_vdev->vdev_guid); + return (err); + } + + if (l2dhdr->dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC)) + byteswap_uint64_array(l2dhdr, sizeof (*l2dhdr)); + + if (l2dhdr->dh_magic != L2ARC_DEV_HDR_MAGIC || + l2dhdr->dh_spa_guid != guid || + l2dhdr->dh_vdev_guid != dev->l2ad_vdev->vdev_guid || + l2dhdr->dh_version != L2ARC_PERSISTENT_VERSION || + l2dhdr->dh_log_entries != dev->l2ad_log_entries || + l2dhdr->dh_end != dev->l2ad_end || + !l2arc_range_check_overlap(dev->l2ad_start, dev->l2ad_end, + l2dhdr->dh_evict) || + (l2dhdr->dh_trim_state != VDEV_TRIM_COMPLETE && + l2arc_trim_ahead > 0)) { + /* + * Attempt to rebuild a device containing no actual dev hdr + * or containing a header from some other pool or from another + * version of persistent L2ARC. + */ + ARCSTAT_BUMP(arcstat_l2_rebuild_abort_unsupported); + return (SET_ERROR(ENOTSUP)); + } + + return (0); +} + +/* + * Reads L2ARC log blocks from storage and validates their contents. + * + * This function implements a simple fetcher to make sure that while + * we're processing one buffer the L2ARC is already fetching the next + * one in the chain. + * + * The arguments this_lp and next_lp point to the current and next log block + * address in the block chain. Similarly, this_lb and next_lb hold the + * l2arc_log_blk_phys_t's of the current and next L2ARC blk. + * + * The `this_io' and `next_io' arguments are used for block fetching. + * When issuing the first blk IO during rebuild, you should pass NULL for + * `this_io'. This function will then issue a sync IO to read the block and + * also issue an async IO to fetch the next block in the block chain. The + * fetched IO is returned in `next_io'. On subsequent calls to this + * function, pass the value returned in `next_io' from the previous call + * as `this_io' and a fresh `next_io' pointer to hold the next fetch IO. + * Prior to the call, you should initialize your `next_io' pointer to be + * NULL. If no fetch IO was issued, the pointer is left set at NULL. + * + * On success, this function returns 0, otherwise it returns an appropriate + * error code. On error the fetching IO is aborted and cleared before + * returning from this function. Therefore, if we return `success', the + * caller can assume that we have taken care of cleanup of fetch IOs. + */ +static int +l2arc_log_blk_read(l2arc_dev_t *dev, + const l2arc_log_blkptr_t *this_lbp, const l2arc_log_blkptr_t *next_lbp, + l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb, + zio_t *this_io, zio_t **next_io) +{ + int err = 0; + zio_cksum_t cksum; + abd_t *abd = NULL; + uint64_t asize; + + ASSERT(this_lbp != NULL && next_lbp != NULL); + ASSERT(this_lb != NULL && next_lb != NULL); + ASSERT(next_io != NULL && *next_io == NULL); + ASSERT(l2arc_log_blkptr_valid(dev, this_lbp)); + + /* + * Check to see if we have issued the IO for this log block in a + * previous run. If not, this is the first call, so issue it now. + */ + if (this_io == NULL) { + this_io = l2arc_log_blk_fetch(dev->l2ad_vdev, this_lbp, + this_lb); + } + + /* + * Peek to see if we can start issuing the next IO immediately. + */ + if (l2arc_log_blkptr_valid(dev, next_lbp)) { + /* + * Start issuing IO for the next log block early - this + * should help keep the L2ARC device busy while we + * decompress and restore this log block. + */ + *next_io = l2arc_log_blk_fetch(dev->l2ad_vdev, next_lbp, + next_lb); + } + + /* Wait for the IO to read this log block to complete */ + if ((err = zio_wait(this_io)) != 0) { + ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors); + zfs_dbgmsg("L2ARC IO error (%d) while reading log block, " + "offset: %llu, vdev guid: %llu", err, this_lbp->lbp_daddr, + dev->l2ad_vdev->vdev_guid); + goto cleanup; + } + + /* + * Make sure the buffer checks out. + * L2BLK_GET_PSIZE returns aligned size for log blocks. + */ + asize = L2BLK_GET_PSIZE((this_lbp)->lbp_prop); + fletcher_4_native(this_lb, asize, NULL, &cksum); + if (!ZIO_CHECKSUM_EQUAL(cksum, this_lbp->lbp_cksum)) { + ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_lb_errors); + zfs_dbgmsg("L2ARC log block cksum failed, offset: %llu, " + "vdev guid: %llu, l2ad_hand: %llu, l2ad_evict: %llu", + this_lbp->lbp_daddr, dev->l2ad_vdev->vdev_guid, + dev->l2ad_hand, dev->l2ad_evict); + err = SET_ERROR(ECKSUM); + goto cleanup; + } + + /* Now we can take our time decoding this buffer */ + switch (L2BLK_GET_COMPRESS((this_lbp)->lbp_prop)) { + case ZIO_COMPRESS_OFF: + break; + case ZIO_COMPRESS_LZ4: + abd = abd_alloc_for_io(asize, B_TRUE); + abd_copy_from_buf_off(abd, this_lb, 0, asize); + if ((err = zio_decompress_data( + L2BLK_GET_COMPRESS((this_lbp)->lbp_prop), + abd, this_lb, asize, sizeof (*this_lb), NULL)) != 0) { + err = SET_ERROR(EINVAL); + goto cleanup; + } + break; + default: + err = SET_ERROR(EINVAL); + goto cleanup; + } + if (this_lb->lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC)) + byteswap_uint64_array(this_lb, sizeof (*this_lb)); + if (this_lb->lb_magic != L2ARC_LOG_BLK_MAGIC) { + err = SET_ERROR(EINVAL); + goto cleanup; + } +cleanup: + /* Abort an in-flight fetch I/O in case of error */ + if (err != 0 && *next_io != NULL) { + l2arc_log_blk_fetch_abort(*next_io); + *next_io = NULL; + } + if (abd != NULL) + abd_free(abd); + return (err); +} + +/* + * Restores the payload of a log block to ARC. This creates empty ARC hdr + * entries which only contain an l2arc hdr, essentially restoring the + * buffers to their L2ARC evicted state. This function also updates space + * usage on the L2ARC vdev to make sure it tracks restored buffers. + */ +static void +l2arc_log_blk_restore(l2arc_dev_t *dev, const l2arc_log_blk_phys_t *lb, + uint64_t lb_asize, uint64_t lb_daddr) +{ + uint64_t size = 0, asize = 0; + uint64_t log_entries = dev->l2ad_log_entries; + + for (int i = log_entries - 1; i >= 0; i--) { + /* + * Restore goes in the reverse temporal direction to preserve + * correct temporal ordering of buffers in the l2ad_buflist. + * l2arc_hdr_restore also does a list_insert_tail instead of + * list_insert_head on the l2ad_buflist: + * + * LIST l2ad_buflist LIST + * HEAD <------ (time) ------ TAIL + * direction +-----+-----+-----+-----+-----+ direction + * of l2arc <== | buf | buf | buf | buf | buf | ===> of rebuild + * fill +-----+-----+-----+-----+-----+ + * ^ ^ + * | | + * | | + * l2arc_feed_thread l2arc_rebuild + * will place new bufs here restores bufs here + * + * During l2arc_rebuild() the device is not used by + * l2arc_feed_thread() as dev->l2ad_rebuild is set to true. + */ + size += L2BLK_GET_LSIZE((&lb->lb_entries[i])->le_prop); + asize += vdev_psize_to_asize(dev->l2ad_vdev, + L2BLK_GET_PSIZE((&lb->lb_entries[i])->le_prop)); + l2arc_hdr_restore(&lb->lb_entries[i], dev); + } + + /* + * Record rebuild stats: + * size Logical size of restored buffers in the L2ARC + * asize Aligned size of restored buffers in the L2ARC + */ + ARCSTAT_INCR(arcstat_l2_rebuild_size, size); + ARCSTAT_INCR(arcstat_l2_rebuild_asize, asize); + ARCSTAT_INCR(arcstat_l2_rebuild_bufs, log_entries); + ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, lb_asize); + ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, asize / lb_asize); + ARCSTAT_BUMP(arcstat_l2_rebuild_log_blks); +} + +/* + * Restores a single ARC buf hdr from a log entry. The ARC buffer is put + * into a state indicating that it has been evicted to L2ARC. + */ +static void +l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, l2arc_dev_t *dev) +{ + arc_buf_hdr_t *hdr, *exists; + kmutex_t *hash_lock; + arc_buf_contents_t type = L2BLK_GET_TYPE((le)->le_prop); + uint64_t asize; + + /* + * Do all the allocation before grabbing any locks, this lets us + * sleep if memory is full and we don't have to deal with failed + * allocations. + */ + hdr = arc_buf_alloc_l2only(L2BLK_GET_LSIZE((le)->le_prop), type, + dev, le->le_dva, le->le_daddr, + L2BLK_GET_PSIZE((le)->le_prop), le->le_birth, + L2BLK_GET_COMPRESS((le)->le_prop), le->le_complevel, + L2BLK_GET_PROTECTED((le)->le_prop), + L2BLK_GET_PREFETCH((le)->le_prop)); + asize = vdev_psize_to_asize(dev->l2ad_vdev, + L2BLK_GET_PSIZE((le)->le_prop)); + + /* + * vdev_space_update() has to be called before arc_hdr_destroy() to + * avoid underflow since the latter also calls the former. + */ + vdev_space_update(dev->l2ad_vdev, asize, 0, 0); + + ARCSTAT_INCR(arcstat_l2_lsize, HDR_GET_LSIZE(hdr)); + ARCSTAT_INCR(arcstat_l2_psize, HDR_GET_PSIZE(hdr)); + + mutex_enter(&dev->l2ad_mtx); + list_insert_tail(&dev->l2ad_buflist, hdr); + (void) zfs_refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); + mutex_exit(&dev->l2ad_mtx); + + exists = buf_hash_insert(hdr, &hash_lock); + if (exists) { + /* Buffer was already cached, no need to restore it. */ + arc_hdr_destroy(hdr); + /* + * If the buffer is already cached, check whether it has + * L2ARC metadata. If not, enter them and update the flag. + * This is important is case of onlining a cache device, since + * we previously evicted all L2ARC metadata from ARC. + */ + if (!HDR_HAS_L2HDR(exists)) { + arc_hdr_set_flags(exists, ARC_FLAG_HAS_L2HDR); + exists->b_l2hdr.b_dev = dev; + exists->b_l2hdr.b_daddr = le->le_daddr; + mutex_enter(&dev->l2ad_mtx); + list_insert_tail(&dev->l2ad_buflist, exists); + (void) zfs_refcount_add_many(&dev->l2ad_alloc, + arc_hdr_size(exists), exists); + mutex_exit(&dev->l2ad_mtx); + vdev_space_update(dev->l2ad_vdev, asize, 0, 0); + ARCSTAT_INCR(arcstat_l2_lsize, HDR_GET_LSIZE(exists)); + ARCSTAT_INCR(arcstat_l2_psize, HDR_GET_PSIZE(exists)); + } + ARCSTAT_BUMP(arcstat_l2_rebuild_bufs_precached); + } + + mutex_exit(hash_lock); +} + +/* + * Starts an asynchronous read IO to read a log block. This is used in log + * block reconstruction to start reading the next block before we are done + * decoding and reconstructing the current block, to keep the l2arc device + * nice and hot with read IO to process. + * The returned zio will contain a newly allocated memory buffers for the IO + * data which should then be freed by the caller once the zio is no longer + * needed (i.e. due to it having completed). If you wish to abort this + * zio, you should do so using l2arc_log_blk_fetch_abort, which takes + * care of disposing of the allocated buffers correctly. + */ +static zio_t * +l2arc_log_blk_fetch(vdev_t *vd, const l2arc_log_blkptr_t *lbp, + l2arc_log_blk_phys_t *lb) +{ + uint32_t asize; + zio_t *pio; + l2arc_read_callback_t *cb; + + /* L2BLK_GET_PSIZE returns aligned size for log blocks */ + asize = L2BLK_GET_PSIZE((lbp)->lbp_prop); + ASSERT(asize <= sizeof (l2arc_log_blk_phys_t)); + + cb = kmem_zalloc(sizeof (l2arc_read_callback_t), KM_SLEEP); + cb->l2rcb_abd = abd_get_from_buf(lb, asize); + pio = zio_root(vd->vdev_spa, l2arc_blk_fetch_done, cb, + ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | + ZIO_FLAG_DONT_RETRY); + (void) zio_nowait(zio_read_phys(pio, vd, lbp->lbp_daddr, asize, + cb->l2rcb_abd, ZIO_CHECKSUM_OFF, NULL, NULL, + ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | + ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE)); + + return (pio); +} + +/* + * Aborts a zio returned from l2arc_log_blk_fetch and frees the data + * buffers allocated for it. + */ +static void +l2arc_log_blk_fetch_abort(zio_t *zio) +{ + (void) zio_wait(zio); +} + +/* + * Creates a zio to update the device header on an l2arc device. + */ +void +l2arc_dev_hdr_update(l2arc_dev_t *dev) +{ + l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr; + const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize; + abd_t *abd; + int err; + + VERIFY(spa_config_held(dev->l2ad_spa, SCL_STATE_ALL, RW_READER)); + + l2dhdr->dh_magic = L2ARC_DEV_HDR_MAGIC; + l2dhdr->dh_version = L2ARC_PERSISTENT_VERSION; + l2dhdr->dh_spa_guid = spa_guid(dev->l2ad_vdev->vdev_spa); + l2dhdr->dh_vdev_guid = dev->l2ad_vdev->vdev_guid; + l2dhdr->dh_log_entries = dev->l2ad_log_entries; + l2dhdr->dh_evict = dev->l2ad_evict; + l2dhdr->dh_start = dev->l2ad_start; + l2dhdr->dh_end = dev->l2ad_end; + l2dhdr->dh_lb_asize = zfs_refcount_count(&dev->l2ad_lb_asize); + l2dhdr->dh_lb_count = zfs_refcount_count(&dev->l2ad_lb_count); + l2dhdr->dh_flags = 0; + l2dhdr->dh_trim_action_time = dev->l2ad_vdev->vdev_trim_action_time; + l2dhdr->dh_trim_state = dev->l2ad_vdev->vdev_trim_state; + if (dev->l2ad_first) + l2dhdr->dh_flags |= L2ARC_DEV_HDR_EVICT_FIRST; + + abd = abd_get_from_buf(l2dhdr, l2dhdr_asize); + + err = zio_wait(zio_write_phys(NULL, dev->l2ad_vdev, + VDEV_LABEL_START_SIZE, l2dhdr_asize, abd, ZIO_CHECKSUM_LABEL, NULL, + NULL, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE)); + + abd_put(abd); + + if (err != 0) { + zfs_dbgmsg("L2ARC IO error (%d) while writing device header, " + "vdev guid: %llu", err, dev->l2ad_vdev->vdev_guid); + } +} + +/* + * Commits a log block to the L2ARC device. This routine is invoked from + * l2arc_write_buffers when the log block fills up. + * This function allocates some memory to temporarily hold the serialized + * buffer to be written. This is then released in l2arc_write_done. + */ +static void +l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, l2arc_write_callback_t *cb) +{ + l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk; + l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr; + uint64_t psize, asize; + zio_t *wzio; + l2arc_lb_abd_buf_t *abd_buf; + uint8_t *tmpbuf; + l2arc_lb_ptr_buf_t *lb_ptr_buf; + + VERIFY3S(dev->l2ad_log_ent_idx, ==, dev->l2ad_log_entries); + + tmpbuf = zio_buf_alloc(sizeof (*lb)); + abd_buf = zio_buf_alloc(sizeof (*abd_buf)); + abd_buf->abd = abd_get_from_buf(lb, sizeof (*lb)); + lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP); + lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t), KM_SLEEP); + + /* link the buffer into the block chain */ + lb->lb_prev_lbp = l2dhdr->dh_start_lbps[1]; + lb->lb_magic = L2ARC_LOG_BLK_MAGIC; + + /* + * l2arc_log_blk_commit() may be called multiple times during a single + * l2arc_write_buffers() call. Save the allocated abd buffers in a list + * so we can free them in l2arc_write_done() later on. + */ + list_insert_tail(&cb->l2wcb_abd_list, abd_buf); + + /* try to compress the buffer */ + psize = zio_compress_data(ZIO_COMPRESS_LZ4, + abd_buf->abd, tmpbuf, sizeof (*lb), 0); + + /* a log block is never entirely zero */ + ASSERT(psize != 0); + asize = vdev_psize_to_asize(dev->l2ad_vdev, psize); + ASSERT(asize <= sizeof (*lb)); + + /* + * Update the start log block pointer in the device header to point + * to the log block we're about to write. + */ + l2dhdr->dh_start_lbps[1] = l2dhdr->dh_start_lbps[0]; + l2dhdr->dh_start_lbps[0].lbp_daddr = dev->l2ad_hand; + l2dhdr->dh_start_lbps[0].lbp_payload_asize = + dev->l2ad_log_blk_payload_asize; + l2dhdr->dh_start_lbps[0].lbp_payload_start = + dev->l2ad_log_blk_payload_start; + _NOTE(CONSTCOND) + L2BLK_SET_LSIZE( + (&l2dhdr->dh_start_lbps[0])->lbp_prop, sizeof (*lb)); + L2BLK_SET_PSIZE( + (&l2dhdr->dh_start_lbps[0])->lbp_prop, asize); + L2BLK_SET_CHECKSUM( + (&l2dhdr->dh_start_lbps[0])->lbp_prop, + ZIO_CHECKSUM_FLETCHER_4); + if (asize < sizeof (*lb)) { + /* compression succeeded */ + bzero(tmpbuf + psize, asize - psize); + L2BLK_SET_COMPRESS( + (&l2dhdr->dh_start_lbps[0])->lbp_prop, + ZIO_COMPRESS_LZ4); + } else { + /* compression failed */ + bcopy(lb, tmpbuf, sizeof (*lb)); + L2BLK_SET_COMPRESS( + (&l2dhdr->dh_start_lbps[0])->lbp_prop, + ZIO_COMPRESS_OFF); + } + + /* checksum what we're about to write */ + fletcher_4_native(tmpbuf, asize, NULL, + &l2dhdr->dh_start_lbps[0].lbp_cksum); + + abd_put(abd_buf->abd); + + /* perform the write itself */ + abd_buf->abd = abd_get_from_buf(tmpbuf, sizeof (*lb)); + abd_take_ownership_of_buf(abd_buf->abd, B_TRUE); + wzio = zio_write_phys(pio, dev->l2ad_vdev, dev->l2ad_hand, + asize, abd_buf->abd, ZIO_CHECKSUM_OFF, NULL, NULL, + ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE); + DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio); + (void) zio_nowait(wzio); + + dev->l2ad_hand += asize; + /* + * Include the committed log block's pointer in the list of pointers + * to log blocks present in the L2ARC device. + */ + bcopy(&l2dhdr->dh_start_lbps[0], lb_ptr_buf->lb_ptr, + sizeof (l2arc_log_blkptr_t)); + mutex_enter(&dev->l2ad_mtx); + list_insert_head(&dev->l2ad_lbptr_list, lb_ptr_buf); + ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize); + ARCSTAT_BUMP(arcstat_l2_log_blk_count); + zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf); + zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf); + mutex_exit(&dev->l2ad_mtx); + vdev_space_update(dev->l2ad_vdev, asize, 0, 0); + + /* bump the kstats */ + ARCSTAT_INCR(arcstat_l2_write_bytes, asize); + ARCSTAT_BUMP(arcstat_l2_log_blk_writes); + ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, asize); + ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, + dev->l2ad_log_blk_payload_asize / asize); + + /* start a new log block */ + dev->l2ad_log_ent_idx = 0; + dev->l2ad_log_blk_payload_asize = 0; + dev->l2ad_log_blk_payload_start = 0; +} + +/* + * Validates an L2ARC log block address to make sure that it can be read + * from the provided L2ARC device. + */ +boolean_t +l2arc_log_blkptr_valid(l2arc_dev_t *dev, const l2arc_log_blkptr_t *lbp) +{ + /* L2BLK_GET_PSIZE returns aligned size for log blocks */ + uint64_t asize = L2BLK_GET_PSIZE((lbp)->lbp_prop); + uint64_t end = lbp->lbp_daddr + asize - 1; + uint64_t start = lbp->lbp_payload_start; + boolean_t evicted = B_FALSE; + + /* + * A log block is valid if all of the following conditions are true: + * - it fits entirely (including its payload) between l2ad_start and + * l2ad_end + * - it has a valid size + * - neither the log block itself nor part of its payload was evicted + * by l2arc_evict(): + * + * l2ad_hand l2ad_evict + * | | lbp_daddr + * | start | | end + * | | | | | + * V V V V V + * l2ad_start ============================================ l2ad_end + * --------------------------|||| + * ^ ^ + * | log block + * payload + */ + + evicted = + l2arc_range_check_overlap(start, end, dev->l2ad_hand) || + l2arc_range_check_overlap(start, end, dev->l2ad_evict) || + l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, start) || + l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, end); + + return (start >= dev->l2ad_start && end <= dev->l2ad_end && + asize > 0 && asize <= sizeof (l2arc_log_blk_phys_t) && + (!evicted || dev->l2ad_first)); +} + +/* + * Inserts ARC buffer header `hdr' into the current L2ARC log block on + * the device. The buffer being inserted must be present in L2ARC. + * Returns B_TRUE if the L2ARC log block is full and needs to be committed + * to L2ARC, or B_FALSE if it still has room for more ARC buffers. + */ +static boolean_t +l2arc_log_blk_insert(l2arc_dev_t *dev, const arc_buf_hdr_t *hdr) +{ + l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk; + l2arc_log_ent_phys_t *le; + + if (dev->l2ad_log_entries == 0) + return (B_FALSE); + + int index = dev->l2ad_log_ent_idx++; + + ASSERT3S(index, <, dev->l2ad_log_entries); + ASSERT(HDR_HAS_L2HDR(hdr)); + + le = &lb->lb_entries[index]; + bzero(le, sizeof (*le)); + le->le_dva = hdr->b_dva; + le->le_birth = hdr->b_birth; + le->le_daddr = hdr->b_l2hdr.b_daddr; + if (index == 0) + dev->l2ad_log_blk_payload_start = le->le_daddr; + L2BLK_SET_LSIZE((le)->le_prop, HDR_GET_LSIZE(hdr)); + L2BLK_SET_PSIZE((le)->le_prop, HDR_GET_PSIZE(hdr)); + L2BLK_SET_COMPRESS((le)->le_prop, HDR_GET_COMPRESS(hdr)); + le->le_complevel = hdr->b_complevel; + L2BLK_SET_TYPE((le)->le_prop, hdr->b_type); + L2BLK_SET_PROTECTED((le)->le_prop, !!(HDR_PROTECTED(hdr))); + L2BLK_SET_PREFETCH((le)->le_prop, !!(HDR_PREFETCH(hdr))); + + dev->l2ad_log_blk_payload_asize += vdev_psize_to_asize(dev->l2ad_vdev, + HDR_GET_PSIZE(hdr)); + + return (dev->l2ad_log_ent_idx == dev->l2ad_log_entries); +} + +/* + * Checks whether a given L2ARC device address sits in a time-sequential + * range. The trick here is that the L2ARC is a rotary buffer, so we can't + * just do a range comparison, we need to handle the situation in which the + * range wraps around the end of the L2ARC device. Arguments: + * bottom -- Lower end of the range to check (written to earlier). + * top -- Upper end of the range to check (written to later). + * check -- The address for which we want to determine if it sits in + * between the top and bottom. + * + * The 3-way conditional below represents the following cases: + * + * bottom < top : Sequentially ordered case: + * <check>--------+-------------------+ + * | (overlap here?) | + * L2ARC dev V V + * |---------------<bottom>============<top>--------------| + * + * bottom > top: Looped-around case: + * <check>--------+------------------+ + * | (overlap here?) | + * L2ARC dev V V + * |===============<top>---------------<bottom>===========| + * ^ ^ + * | (or here?) | + * +---------------+---------<check> + * + * top == bottom : Just a single address comparison. + */ +boolean_t +l2arc_range_check_overlap(uint64_t bottom, uint64_t top, uint64_t check) +{ + if (bottom < top) + return (bottom <= check && check <= top); + else if (bottom > top) + return (check <= top || bottom <= check); + else + return (check == top); +} + +EXPORT_SYMBOL(arc_buf_size); +EXPORT_SYMBOL(arc_write); +EXPORT_SYMBOL(arc_read); +EXPORT_SYMBOL(arc_buf_info); +EXPORT_SYMBOL(arc_getbuf_func); +EXPORT_SYMBOL(arc_add_prune_callback); +EXPORT_SYMBOL(arc_remove_prune_callback); + +/* BEGIN CSTYLED */ +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min, param_set_arc_long, + param_get_long, ZMOD_RW, "Min arc size"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, max, param_set_arc_long, + param_get_long, ZMOD_RW, "Max arc size"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, meta_limit, param_set_arc_long, + param_get_long, ZMOD_RW, "Metadata limit for arc size"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, meta_limit_percent, + param_set_arc_long, param_get_long, ZMOD_RW, + "Percent of arc size for arc meta limit"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, meta_min, param_set_arc_long, + param_get_long, ZMOD_RW, "Min arc metadata"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_prune, INT, ZMOD_RW, + "Meta objects to scan for prune"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_adjust_restarts, INT, ZMOD_RW, + "Limit number of restarts in arc_evict_meta"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_strategy, INT, ZMOD_RW, + "Meta reclaim strategy"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, grow_retry, param_set_arc_int, + param_get_int, ZMOD_RW, "Seconds before growing arc size"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, p_dampener_disable, INT, ZMOD_RW, + "Disable arc_p adapt dampener"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, shrink_shift, param_set_arc_int, + param_get_int, ZMOD_RW, "log2(fraction of arc to reclaim)"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, pc_percent, UINT, ZMOD_RW, + "Percent of pagecache to reclaim arc to"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, p_min_shift, param_set_arc_int, + param_get_int, ZMOD_RW, "arc_c shift to calc min/max arc_p"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, average_blocksize, INT, ZMOD_RD, + "Target average block size"); + +ZFS_MODULE_PARAM(zfs, zfs_, compressed_arc_enabled, INT, ZMOD_RW, + "Disable compressed arc buffers"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min_prefetch_ms, param_set_arc_int, + param_get_int, ZMOD_RW, "Min life of prefetch block in ms"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min_prescient_prefetch_ms, + param_set_arc_int, param_get_int, ZMOD_RW, + "Min life of prescient prefetched block in ms"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, write_max, ULONG, ZMOD_RW, + "Max write bytes per interval"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, write_boost, ULONG, ZMOD_RW, + "Extra write bytes during device warmup"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, headroom, ULONG, ZMOD_RW, + "Number of max device writes to precache"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, headroom_boost, ULONG, ZMOD_RW, + "Compressed l2arc_headroom multiplier"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, trim_ahead, ULONG, ZMOD_RW, + "TRIM ahead L2ARC write size multiplier"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, feed_secs, ULONG, ZMOD_RW, + "Seconds between L2ARC writing"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, feed_min_ms, ULONG, ZMOD_RW, + "Min feed interval in milliseconds"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, noprefetch, INT, ZMOD_RW, + "Skip caching prefetched buffers"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, feed_again, INT, ZMOD_RW, + "Turbo L2ARC warmup"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, norw, INT, ZMOD_RW, + "No reads during writes"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, rebuild_enabled, INT, ZMOD_RW, + "Rebuild the L2ARC when importing a pool"); + +ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, rebuild_blocks_min_l2size, ULONG, ZMOD_RW, + "Min size in bytes to write rebuild log blocks in L2ARC"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, lotsfree_percent, param_set_arc_int, + param_get_int, ZMOD_RW, "System free memory I/O throttle in bytes"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, sys_free, param_set_arc_long, + param_get_long, ZMOD_RW, "System free memory target size in bytes"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, dnode_limit, param_set_arc_long, + param_get_long, ZMOD_RW, "Minimum bytes of dnodes in arc"); + +ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, dnode_limit_percent, + param_set_arc_long, param_get_long, ZMOD_RW, + "Percent of ARC meta buffers for dnodes"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, dnode_reduce_percent, ULONG, ZMOD_RW, + "Percentage of excess dnodes to try to unpin"); + +ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, eviction_pct, INT, ZMOD_RW, + "When full, ARC allocation waits for eviction of this % of alloc size"); +/* END CSTYLED */ |