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Diffstat (limited to 'sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c')
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1 files changed, 8542 insertions, 0 deletions
diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c new file mode 100644 index 000000000000..0a62df056071 --- /dev/null +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c @@ -0,0 +1,8542 @@ +/* + * 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, 2018 by Delphix. All rights reserved. + * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. + * Copyright 2017 Nexenta Systems, Inc. All rights reserved. + */ + +/* + * 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 (rangeing 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. + */ + +#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/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> +#ifdef _KERNEL +#include <sys/dnlc.h> +#include <sys/racct.h> +#endif +#include <sys/callb.h> +#include <sys/kstat.h> +#include <sys/trim_map.h> +#include <sys/zthr.h> +#include <zfs_fletcher.h> +#include <sys/sdt.h> +#include <sys/aggsum.h> +#include <sys/cityhash.h> + +#include <machine/vmparam.h> + +#ifdef illumos +#ifndef _KERNEL +/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ +boolean_t arc_watch = B_FALSE; +int arc_procfd; +#endif +#endif /* illumos */ + +/* + * This thread's job is to keep enough free memory in the system, by + * calling arc_kmem_reap_now() plus arc_shrink(), 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_adjust(), which improves arc_is_overflowing(). + */ +static zthr_t *arc_adjust_zthr; + +static kmutex_t arc_adjust_lock; +static kcondvar_t arc_adjust_waiters_cv; +static boolean_t arc_adjust_needed = B_FALSE; + +static kmutex_t arc_dnlc_evicts_lock; +static kcondvar_t arc_dnlc_evicts_cv; +static boolean_t arc_dnlc_evicts_thread_exit; + +uint_t arc_reduce_dnlc_percent = 3; + +/* + * 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 = 60; + +/* + * Minimum time between calls to arc_kmem_reap_soon(). Note that this will + * be converted to ticks, so with the default hz=100, a setting of 15 ms + * will actually wait 2 ticks, or 20ms. + */ +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; + +/* + * 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 zfs_arc_min_prefetch_ms = 1; +static int zfs_arc_min_prescient_prefetch_ms = 6; + +/* + * If this percent of memory is free, don't throttle. + */ +int arc_lotsfree_percent = 10; + +static boolean_t arc_initialized; +extern boolean_t zfs_prefetch_disable; + +/* + * The arc has filled available memory and has now warmed up. + */ +static boolean_t arc_warm; + +/* + * log2 fraction of the zio arena to keep free. + */ +int arc_zio_arena_free_shift = 2; + +/* + * These tunables are for performance analysis. + */ +uint64_t zfs_arc_max; +uint64_t zfs_arc_min; +uint64_t zfs_arc_meta_limit = 0; +uint64_t zfs_arc_meta_min = 0; +uint64_t zfs_arc_dnode_limit = 0; +uint64_t zfs_arc_dnode_reduce_percent = 10; +int zfs_arc_grow_retry = 0; +int zfs_arc_shrink_shift = 0; +int zfs_arc_no_grow_shift = 0; +int zfs_arc_p_min_shift = 0; +uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ +u_int zfs_arc_free_target = 0; + +/* Absolute min for arc min / max is 16MB. */ +static uint64_t arc_abs_min = 16 << 20; + +/* + * ARC dirty data constraints for arc_tempreserve_space() throttle + */ +uint_t zfs_arc_dirty_limit_percent = 50; /* total dirty data limit */ +uint_t zfs_arc_anon_limit_percent = 25; /* anon block dirty limit */ +uint_t zfs_arc_pool_dirty_percent = 20; /* each pool's anon allowance */ + +boolean_t zfs_compressed_arc_enabled = B_TRUE; + +static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); +static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); +static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); +static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); +static int sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS); + +#if defined(__FreeBSD__) && defined(_KERNEL) +static void +arc_free_target_init(void *unused __unused) +{ + + zfs_arc_free_target = vm_cnt.v_free_target; +} +SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, + arc_free_target_init, NULL); + +TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); +TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); +TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); +TUNABLE_INT("vfs.zfs.arc_grow_retry", &zfs_arc_grow_retry); +TUNABLE_INT("vfs.zfs.arc_no_grow_shift", &zfs_arc_no_grow_shift); +SYSCTL_DECL(_vfs_zfs); +SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, + 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); +SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, + 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); +SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_no_grow_shift, CTLTYPE_U32 | CTLFLAG_RWTUN, + 0, sizeof(uint32_t), sysctl_vfs_zfs_arc_no_grow_shift, "U", + "log2(fraction of ARC which must be free to allow growing)"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, + &zfs_arc_average_blocksize, 0, + "ARC average blocksize"); +SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, + &arc_shrink_shift, 0, + "log2(fraction of arc to reclaim)"); +SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_grow_retry, CTLFLAG_RW, + &arc_grow_retry, 0, + "Wait in seconds before considering growing ARC"); +SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, + &zfs_compressed_arc_enabled, 0, + "Enable compressed ARC"); +SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_kmem_cache_reap_retry_ms, CTLFLAG_RWTUN, + &arc_kmem_cache_reap_retry_ms, 0, + "Interval between ARC kmem_cache reapings"); + +/* + * We don't have a tunable for arc_free_target due to the dependency on + * pagedaemon initialisation. + */ +SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, + CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), + sysctl_vfs_zfs_arc_free_target, "IU", + "Desired number of free pages below which ARC triggers reclaim"); + +static int +sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) +{ + u_int val; + int err; + + val = zfs_arc_free_target; + err = sysctl_handle_int(oidp, &val, 0, req); + if (err != 0 || req->newptr == NULL) + return (err); + + if (val < minfree) + return (EINVAL); + if (val > vm_cnt.v_page_count) + return (EINVAL); + + zfs_arc_free_target = val; + + return (0); +} + +/* + * Must be declared here, before the definition of corresponding kstat + * macro which uses the same names will confuse the compiler. + */ +SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, + CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), + sysctl_vfs_zfs_arc_meta_limit, "QU", + "ARC metadata limit"); +#endif + +/* + * Note that buffers can be in one of 6 states: + * ARC_anon - anonymous (discussed below) + * ARC_mru - recently used, currently cached + * ARC_mru_ghost - recentely used, no longer in cache + * ARC_mfu - frequently used, currently cached + * ARC_mfu_ghost - frequently used, no longer in cache + * ARC_l2c_only - exists in L2ARC but not other states + * When there are no active references to the buffer, they are + * are linked onto a list in one of these arc states. These are + * the only buffers that can be evicted or deleted. Within each + * state there are multiple lists, one for meta-data and one for + * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, + * etc.) is tracked separately so that it can be managed more + * explicitly: favored over data, limited explicitly. + * + * Anonymous buffers are buffers that are not associated with + * a DVA. These are buffers that hold dirty block copies + * before they are written to stable storage. By definition, + * they are "ref'd" and are considered part of arc_mru + * that cannot be freed. Generally, they will aquire a DVA + * as they are written and migrate onto the arc_mru list. + * + * The ARC_l2c_only state is for buffers that are in the second + * level ARC but no longer in any of the ARC_m* lists. The second + * level ARC itself may also contain buffers that are in any of + * the ARC_m* states - meaning that a buffer can exist in two + * places. The reason for the ARC_l2c_only state is to keep the + * buffer header in the hash table, so that reads that hit the + * second level ARC benefit from these fast lookups. + */ + +typedef struct arc_state { + /* + * list of evictable buffers + */ + multilist_t *arcs_list[ARC_BUFC_NUMTYPES]; + /* + * total amount of evictable data in this state + */ + refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; + /* + * total amount of data in this state; this includes: evictable, + * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. + */ + refcount_t arcs_size; + /* + * supports the "dbufs" kstat + */ + arc_state_type_t arcs_state; +} arc_state_t; + +/* + * Percentage that can be consumed by dnodes of ARC meta buffers. + */ +int zfs_arc_meta_prune = 10000; +unsigned long zfs_arc_dnode_limit_percent = 10; +int zfs_arc_meta_strategy = ARC_STRATEGY_META_ONLY; +int zfs_arc_meta_adjust_restarts = 4096; + +SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_meta_strategy, CTLFLAG_RWTUN, + &zfs_arc_meta_strategy, 0, + "ARC metadata reclamation strategy " + "(0 = metadata only, 1 = balance data and metadata)"); + +/* The 6 states: */ +static arc_state_t ARC_anon; +static arc_state_t ARC_mru; +static arc_state_t ARC_mru_ghost; +static arc_state_t ARC_mfu; +static arc_state_t ARC_mfu_ghost; +static arc_state_t ARC_l2c_only; + +typedef struct arc_stats { + kstat_named_t arcstat_hits; + kstat_named_t arcstat_misses; + kstat_named_t arcstat_demand_data_hits; + kstat_named_t arcstat_demand_data_misses; + kstat_named_t arcstat_demand_metadata_hits; + kstat_named_t arcstat_demand_metadata_misses; + kstat_named_t arcstat_prefetch_data_hits; + kstat_named_t arcstat_prefetch_data_misses; + kstat_named_t arcstat_prefetch_metadata_hits; + kstat_named_t arcstat_prefetch_metadata_misses; + kstat_named_t arcstat_mru_hits; + kstat_named_t arcstat_mru_ghost_hits; + kstat_named_t arcstat_mfu_hits; + kstat_named_t arcstat_mfu_ghost_hits; + kstat_named_t arcstat_allocated; + kstat_named_t arcstat_deleted; + /* + * Number of buffers that could not be evicted because the hash lock + * was held by another thread. The lock may not necessarily be held + * by something using the same buffer, since hash locks are shared + * by multiple buffers. + */ + kstat_named_t arcstat_mutex_miss; + /* + * Number of buffers skipped when updating the access state due to the + * header having already been released after acquiring the hash lock. + */ + kstat_named_t arcstat_access_skip; + /* + * Number of buffers skipped because they have I/O in progress, are + * indirect prefetch buffers that have not lived long enough, or are + * not from the spa we're trying to evict from. + */ + kstat_named_t arcstat_evict_skip; + /* + * Number of times arc_evict_state() was unable to evict enough + * buffers to reach it's target amount. + */ + kstat_named_t arcstat_evict_not_enough; + kstat_named_t arcstat_evict_l2_cached; + kstat_named_t arcstat_evict_l2_eligible; + kstat_named_t arcstat_evict_l2_ineligible; + kstat_named_t arcstat_evict_l2_skip; + kstat_named_t arcstat_hash_elements; + kstat_named_t arcstat_hash_elements_max; + kstat_named_t arcstat_hash_collisions; + kstat_named_t arcstat_hash_chains; + kstat_named_t arcstat_hash_chain_max; + kstat_named_t arcstat_p; + kstat_named_t arcstat_c; + kstat_named_t arcstat_c_min; + kstat_named_t arcstat_c_max; + /* Not updated directly; only synced in arc_kstat_update. */ + kstat_named_t arcstat_size; + /* + * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd. + * Note that the compressed bytes may match the uncompressed bytes + * if the block is either not compressed or compressed arc is disabled. + */ + kstat_named_t arcstat_compressed_size; + /* + * Uncompressed size of the data stored in b_pabd. If compressed + * arc is disabled then this value will be identical to the stat + * above. + */ + kstat_named_t arcstat_uncompressed_size; + /* + * Number of bytes stored in all the arc_buf_t's. This is classified + * as "overhead" since this data is typically short-lived and will + * be evicted from the arc when it becomes unreferenced unless the + * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level + * values have been set (see comment in dbuf.c for more information). + */ + kstat_named_t arcstat_overhead_size; + /* + * Number of bytes consumed by internal ARC structures necessary + * for tracking purposes; these structures are not actually + * backed by ARC buffers. This includes arc_buf_hdr_t structures + * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only + * caches), and arc_buf_t structures (allocated via arc_buf_t + * cache). + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_hdr_size; + /* + * Number of bytes consumed by ARC buffers of type equal to + * ARC_BUFC_DATA. This is generally consumed by buffers backing + * on disk user data (e.g. plain file contents). + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_data_size; + /* + * Number of bytes consumed by ARC buffers of type equal to + * ARC_BUFC_METADATA. This is generally consumed by buffers + * backing on disk data that is used for internal ZFS + * structures (e.g. ZAP, dnode, indirect blocks, etc). + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_metadata_size; + /* + * Number of bytes consumed by dmu_buf_impl_t objects. + */ + kstat_named_t arcstat_dbuf_size; + /* + * Number of bytes consumed by dnode_t objects. + */ + kstat_named_t arcstat_dnode_size; + /* + * Number of bytes consumed by bonus buffers. + */ + kstat_named_t arcstat_bonus_size; +#if defined(__FreeBSD__) && defined(COMPAT_FREEBSD11) + /* + * Sum of the previous three counters, provided for compatibility. + */ + kstat_named_t arcstat_other_size; +#endif + /* + * Total number of bytes consumed by ARC buffers residing in the + * arc_anon state. This includes *all* buffers in the arc_anon + * state; e.g. data, metadata, evictable, and unevictable buffers + * are all included in this value. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_anon_size; + /* + * Number of bytes consumed by ARC buffers that meet the + * following criteria: backing buffers of type ARC_BUFC_DATA, + * residing in the arc_anon state, and are eligible for eviction + * (e.g. have no outstanding holds on the buffer). + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_anon_evictable_data; + /* + * Number of bytes consumed by ARC buffers that meet the + * following criteria: backing buffers of type ARC_BUFC_METADATA, + * residing in the arc_anon state, and are eligible for eviction + * (e.g. have no outstanding holds on the buffer). + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_anon_evictable_metadata; + /* + * Total number of bytes consumed by ARC buffers residing in the + * arc_mru state. This includes *all* buffers in the arc_mru + * state; e.g. data, metadata, evictable, and unevictable buffers + * are all included in this value. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mru_size; + /* + * Number of bytes consumed by ARC buffers that meet the + * following criteria: backing buffers of type ARC_BUFC_DATA, + * residing in the arc_mru state, and are eligible for eviction + * (e.g. have no outstanding holds on the buffer). + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mru_evictable_data; + /* + * Number of bytes consumed by ARC buffers that meet the + * following criteria: backing buffers of type ARC_BUFC_METADATA, + * residing in the arc_mru state, and are eligible for eviction + * (e.g. have no outstanding holds on the buffer). + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mru_evictable_metadata; + /* + * Total number of bytes that *would have been* consumed by ARC + * buffers in the arc_mru_ghost state. The key thing to note + * here, is the fact that this size doesn't actually indicate + * RAM consumption. The ghost lists only consist of headers and + * don't actually have ARC buffers linked off of these headers. + * Thus, *if* the headers had associated ARC buffers, these + * buffers *would have* consumed this number of bytes. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mru_ghost_size; + /* + * Number of bytes that *would have been* consumed by ARC + * buffers that are eligible for eviction, of type + * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mru_ghost_evictable_data; + /* + * Number of bytes that *would have been* consumed by ARC + * buffers that are eligible for eviction, of type + * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mru_ghost_evictable_metadata; + /* + * Total number of bytes consumed by ARC buffers residing in the + * arc_mfu state. This includes *all* buffers in the arc_mfu + * state; e.g. data, metadata, evictable, and unevictable buffers + * are all included in this value. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mfu_size; + /* + * Number of bytes consumed by ARC buffers that are eligible for + * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu + * state. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mfu_evictable_data; + /* + * Number of bytes consumed by ARC buffers that are eligible for + * eviction, of type ARC_BUFC_METADATA, and reside in the + * arc_mfu state. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mfu_evictable_metadata; + /* + * Total number of bytes that *would have been* consumed by ARC + * buffers in the arc_mfu_ghost state. See the comment above + * arcstat_mru_ghost_size for more details. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mfu_ghost_size; + /* + * Number of bytes that *would have been* consumed by ARC + * buffers that are eligible for eviction, of type + * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mfu_ghost_evictable_data; + /* + * Number of bytes that *would have been* consumed by ARC + * buffers that are eligible for eviction, of type + * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. + * Not updated directly; only synced in arc_kstat_update. + */ + kstat_named_t arcstat_mfu_ghost_evictable_metadata; + kstat_named_t arcstat_l2_hits; + kstat_named_t arcstat_l2_misses; + kstat_named_t arcstat_l2_feeds; + kstat_named_t arcstat_l2_rw_clash; + kstat_named_t arcstat_l2_read_bytes; + kstat_named_t arcstat_l2_write_bytes; + kstat_named_t arcstat_l2_writes_sent; + kstat_named_t arcstat_l2_writes_done; + kstat_named_t arcstat_l2_writes_error; + kstat_named_t arcstat_l2_writes_lock_retry; + kstat_named_t arcstat_l2_evict_lock_retry; + kstat_named_t arcstat_l2_evict_reading; + kstat_named_t arcstat_l2_evict_l1cached; + kstat_named_t arcstat_l2_free_on_write; + kstat_named_t arcstat_l2_abort_lowmem; + kstat_named_t arcstat_l2_cksum_bad; + kstat_named_t arcstat_l2_io_error; + kstat_named_t arcstat_l2_lsize; + kstat_named_t arcstat_l2_psize; + /* Not updated directly; only synced in arc_kstat_update. */ + kstat_named_t arcstat_l2_hdr_size; + kstat_named_t arcstat_l2_write_trylock_fail; + kstat_named_t arcstat_l2_write_passed_headroom; + kstat_named_t arcstat_l2_write_spa_mismatch; + kstat_named_t arcstat_l2_write_in_l2; + kstat_named_t arcstat_l2_write_hdr_io_in_progress; + kstat_named_t arcstat_l2_write_not_cacheable; + kstat_named_t arcstat_l2_write_full; + kstat_named_t arcstat_l2_write_buffer_iter; + kstat_named_t arcstat_l2_write_pios; + kstat_named_t arcstat_l2_write_buffer_bytes_scanned; + kstat_named_t arcstat_l2_write_buffer_list_iter; + kstat_named_t arcstat_l2_write_buffer_list_null_iter; + kstat_named_t arcstat_memory_throttle_count; + kstat_named_t arcstat_memory_direct_count; + kstat_named_t arcstat_memory_indirect_count; + kstat_named_t arcstat_memory_all_bytes; + kstat_named_t arcstat_memory_free_bytes; + kstat_named_t arcstat_memory_available_bytes; + kstat_named_t arcstat_no_grow; + kstat_named_t arcstat_tempreserve; + kstat_named_t arcstat_loaned_bytes; + kstat_named_t arcstat_prune; + /* Not updated directly; only synced in arc_kstat_update. */ + kstat_named_t arcstat_meta_used; + kstat_named_t arcstat_meta_limit; + kstat_named_t arcstat_dnode_limit; + kstat_named_t arcstat_meta_max; + kstat_named_t arcstat_meta_min; + kstat_named_t arcstat_async_upgrade_sync; + kstat_named_t arcstat_demand_hit_predictive_prefetch; + kstat_named_t arcstat_demand_hit_prescient_prefetch; +} arc_stats_t; + +static 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 }, + { "allocated", 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(__FreeBSD__) && 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_write_trylock_fail", KSTAT_DATA_UINT64 }, + { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, + { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, + { "l2_write_in_l2", KSTAT_DATA_UINT64 }, + { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, + { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, + { "l2_write_full", KSTAT_DATA_UINT64 }, + { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, + { "l2_write_pios", KSTAT_DATA_UINT64 }, + { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, + { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, + { "l2_write_buffer_list_null_iter", 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_UINT64 }, + { "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 }, +}; + +#define ARCSTAT(stat) (arc_stats.stat.value.ui64) + +#define ARCSTAT_INCR(stat, val) \ + atomic_add_64(&arc_stats.stat.value.ui64, (val)) + +#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) +#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) + +#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);\ + } \ + } + +kstat_t *arc_ksp; +static arc_state_t *arc_anon; +static arc_state_t *arc_mru; +static arc_state_t *arc_mru_ghost; +static arc_state_t *arc_mfu; +static arc_state_t *arc_mfu_ghost; +static arc_state_t *arc_l2c_only; + +/* + * 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_p ARCSTAT(arcstat_p) /* target size of MRU */ +#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ +#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ +#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ +#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ +#define arc_dnode_limit ARCSTAT(arcstat_dnode_limit) /* max size for dnodes */ +#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_dbuf_size ARCSTAT(arcstat_dbuf_size) /* dbuf metadata */ +#define arc_dnode_size ARCSTAT(arcstat_dnode_size) /* dnode metadata */ +#define arc_bonus_size ARCSTAT(arcstat_bonus_size) /* bonus buffer metadata */ + +/* 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_hdr_size; +aggsum_t astat_bonus_size; +aggsum_t astat_dnode_size; +aggsum_t astat_dbuf_size; +aggsum_t astat_l2_hdr_size; + +static list_t arc_prune_list; +static kmutex_t arc_prune_mtx; +static taskq_t *arc_prune_taskq; + +static int arc_no_grow; /* Don't try to grow cache size */ +static hrtime_t arc_growtime; +static uint64_t arc_tempreserve; +static uint64_t arc_loaned_bytes; + +typedef struct arc_callback arc_callback_t; + +struct arc_callback { + void *acb_private; + arc_read_done_func_t *acb_done; + arc_buf_t *acb_buf; + boolean_t acb_compressed; + zio_t *acb_zio_dummy; + zio_t *acb_zio_head; + arc_callback_t *acb_next; +}; + +typedef struct arc_write_callback arc_write_callback_t; + +struct arc_write_callback { + void *awcb_private; + arc_write_done_func_t *awcb_ready; + arc_write_done_func_t *awcb_children_ready; + arc_write_done_func_t *awcb_physdone; + arc_write_done_func_t *awcb_done; + arc_buf_t *awcb_buf; +}; + +/* + * ARC buffers are separated into multiple structs as a memory saving measure: + * - Common fields struct, always defined, and embedded within it: + * - L2-only fields, always allocated but undefined when not in L2ARC + * - L1-only fields, only allocated when in L1ARC + * + * Buffer in L1 Buffer only in L2 + * +------------------------+ +------------------------+ + * | arc_buf_hdr_t | | arc_buf_hdr_t | + * | | | | + * | | | | + * | | | | + * +------------------------+ +------------------------+ + * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | + * | (undefined if L1-only) | | | + * +------------------------+ +------------------------+ + * | l1arc_buf_hdr_t | + * | | + * | | + * | | + * | | + * +------------------------+ + * + * Because it's possible for the L2ARC to become extremely large, we can wind + * up eating a lot of memory in L2ARC buffer headers, so the size of a header + * is minimized by only allocating the fields necessary for an L1-cached buffer + * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and + * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple + * words in pointers. arc_hdr_realloc() is used to switch a header between + * these two allocation states. + */ +typedef struct l1arc_buf_hdr { + kmutex_t b_freeze_lock; + zio_cksum_t *b_freeze_cksum; +#ifdef ZFS_DEBUG + /* + * Used for debugging with kmem_flags - by allocating and freeing + * b_thawed when the buffer is thawed, we get a record of the stack + * trace that thawed it. + */ + void *b_thawed; +#endif + + arc_buf_t *b_buf; + uint32_t b_bufcnt; + /* for waiting on writes to complete */ + kcondvar_t b_cv; + uint8_t b_byteswap; + + /* protected by arc state mutex */ + arc_state_t *b_state; + multilist_node_t b_arc_node; + + /* updated atomically */ + clock_t b_arc_access; + uint32_t b_mru_hits; + uint32_t b_mru_ghost_hits; + uint32_t b_mfu_hits; + uint32_t b_mfu_ghost_hits; + uint32_t b_l2_hits; + + /* self protecting */ + refcount_t b_refcnt; + + arc_callback_t *b_acb; + abd_t *b_pabd; +} l1arc_buf_hdr_t; + +typedef struct l2arc_dev l2arc_dev_t; + +typedef struct l2arc_buf_hdr { + /* protected by arc_buf_hdr mutex */ + l2arc_dev_t *b_dev; /* L2ARC device */ + uint64_t b_daddr; /* disk address, offset byte */ + uint32_t b_hits; + + list_node_t b_l2node; +} l2arc_buf_hdr_t; + +struct arc_buf_hdr { + /* protected by hash lock */ + dva_t b_dva; + uint64_t b_birth; + + arc_buf_contents_t b_type; + arc_buf_hdr_t *b_hash_next; + arc_flags_t b_flags; + + /* + * This field stores the size of the data buffer after + * compression, and is set in the arc's zio completion handlers. + * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). + * + * While the block pointers can store up to 32MB in their psize + * field, we can only store up to 32MB minus 512B. This is due + * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. + * a field of zeros represents 512B in the bp). We can't use a + * bias of 1 since we need to reserve a psize of zero, here, to + * represent holes and embedded blocks. + * + * This isn't a problem in practice, since the maximum size of a + * buffer is limited to 16MB, so we never need to store 32MB in + * this field. Even in the upstream illumos code base, the + * maximum size of a buffer is limited to 16MB. + */ + uint16_t b_psize; + + /* + * This field stores the size of the data buffer before + * compression, and cannot change once set. It is in units + * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) + */ + uint16_t b_lsize; /* immutable */ + uint64_t b_spa; /* immutable */ + + /* L2ARC fields. Undefined when not in L2ARC. */ + l2arc_buf_hdr_t b_l2hdr; + /* L1ARC fields. Undefined when in l2arc_only state */ + l1arc_buf_hdr_t b_l1hdr; +}; + +#if defined(__FreeBSD__) && defined(_KERNEL) +static int +sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) +{ + uint64_t val; + int err; + + val = arc_meta_limit; + err = sysctl_handle_64(oidp, &val, 0, req); + if (err != 0 || req->newptr == NULL) + return (err); + + if (val <= 0 || val > arc_c_max) + return (EINVAL); + + arc_meta_limit = val; + return (0); +} + +static int +sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS) +{ + uint32_t val; + int err; + + val = arc_no_grow_shift; + err = sysctl_handle_32(oidp, &val, 0, req); + if (err != 0 || req->newptr == NULL) + return (err); + + if (val >= arc_shrink_shift) + return (EINVAL); + + arc_no_grow_shift = val; + return (0); +} + +static int +sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) +{ + uint64_t val; + int err; + + val = zfs_arc_max; + err = sysctl_handle_64(oidp, &val, 0, req); + if (err != 0 || req->newptr == NULL) + return (err); + + if (zfs_arc_max == 0) { + /* Loader tunable so blindly set */ + zfs_arc_max = val; + return (0); + } + + if (val < arc_abs_min || val > kmem_size()) + return (EINVAL); + if (val < arc_c_min) + return (EINVAL); + if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) + return (EINVAL); + + arc_c_max = val; + + arc_c = arc_c_max; + arc_p = (arc_c >> 1); + + if (zfs_arc_meta_limit == 0) { + /* limit meta-data to 1/4 of the arc capacity */ + arc_meta_limit = arc_c_max / 4; + } + + /* if kmem_flags are set, lets try to use less memory */ + if (kmem_debugging()) + arc_c = arc_c / 2; + + zfs_arc_max = arc_c; + + return (0); +} + +static int +sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) +{ + uint64_t val; + int err; + + val = zfs_arc_min; + err = sysctl_handle_64(oidp, &val, 0, req); + if (err != 0 || req->newptr == NULL) + return (err); + + if (zfs_arc_min == 0) { + /* Loader tunable so blindly set */ + zfs_arc_min = val; + return (0); + } + + if (val < arc_abs_min || val > arc_c_max) + return (EINVAL); + + arc_c_min = val; + + if (zfs_arc_meta_min == 0) + arc_meta_min = arc_c_min / 2; + + if (arc_c < arc_c_min) + arc_c = arc_c_min; + + zfs_arc_min = arc_c_min; + + return (0); +} +#endif + +#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_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) + +/* 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) + +/* + * Other sizes + */ + +#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) +#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) + +/* + * Hash table routines + */ + +#define HT_LOCK_PAD CACHE_LINE_SIZE + +struct ht_lock { + kmutex_t ht_lock; +#ifdef _KERNEL + unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; +#endif +}; + +#define BUF_LOCKS 256 +typedef struct buf_hash_table { + uint64_t ht_mask; + arc_buf_hdr_t **ht_table; + struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); +} 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 */ + +#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) +#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) + +/* L2ARC Performance Tunables */ +uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ +uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ +uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ +uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; +uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ +uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ +boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ +boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ +boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ + +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RWTUN, + &l2arc_write_max, 0, "max write size"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RWTUN, + &l2arc_write_boost, 0, "extra write during warmup"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RWTUN, + &l2arc_headroom, 0, "number of dev writes"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RWTUN, + &l2arc_feed_secs, 0, "interval seconds"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RWTUN, + &l2arc_feed_min_ms, 0, "min interval milliseconds"); + +SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RWTUN, + &l2arc_noprefetch, 0, "don't cache prefetch bufs"); +SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RWTUN, + &l2arc_feed_again, 0, "turbo warmup"); +SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RWTUN, + &l2arc_norw, 0, "no reads during writes"); + +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, + &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, + &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, + "size of anonymous state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, + &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, + "size of anonymous state"); + +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, + &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, + &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, + "size of metadata in mru state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, + &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, + "size of data in mru state"); + +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, + &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, + &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, + "size of metadata in mru ghost state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, + &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, + "size of data in mru ghost state"); + +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, + &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, + &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, + "size of metadata in mfu state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, + &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, + "size of data in mfu state"); + +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, + &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, + &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, + "size of metadata in mfu ghost state"); +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, + &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, + "size of data in mfu ghost state"); + +SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, + &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); + +SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prefetch_ms, CTLFLAG_RW, + &zfs_arc_min_prefetch_ms, 0, "Min life of prefetch block in ms"); +SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prescient_prefetch_ms, CTLFLAG_RW, + &zfs_arc_min_prescient_prefetch_ms, 0, "Min life of prescient prefetched block in ms"); + +/* + * L2ARC Internals + */ +struct l2arc_dev { + vdev_t *l2ad_vdev; /* vdev */ + spa_t *l2ad_spa; /* spa */ + uint64_t l2ad_hand; /* next write location */ + uint64_t l2ad_start; /* first addr on device */ + uint64_t l2ad_end; /* last addr on device */ + boolean_t l2ad_first; /* first sweep through */ + boolean_t l2ad_writing; /* currently writing */ + kmutex_t l2ad_mtx; /* lock for buffer list */ + list_t l2ad_buflist; /* buffer list */ + list_node_t l2ad_node; /* device list node */ + refcount_t l2ad_alloc; /* allocated bytes */ +}; + +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_write_callback { + l2arc_dev_t *l2wcb_dev; /* device info */ + arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ +} l2arc_write_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; + +static kmutex_t l2arc_feed_thr_lock; +static kcondvar_t l2arc_feed_thr_cv; +static uint8_t l2arc_thread_exit; + +static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *); +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 *); +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_pabd(arc_buf_hdr_t *); +static void arc_hdr_alloc_pabd(arc_buf_hdr_t *); +static void arc_access(arc_buf_hdr_t *, kmutex_t *); +static boolean_t arc_is_overflowing(); +static void arc_buf_watch(arc_buf_t *); +static void arc_prune_async(int64_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_trim(const arc_buf_hdr_t *hdr) +{ + l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; + + ASSERT(HDR_HAS_L2HDR(hdr)); + ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); + + if (HDR_GET_PSIZE(hdr) != 0) { + trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, + HDR_GET_PSIZE(hdr), 0); + } +} + +/* + * 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_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_l2only_cache; +static kmem_cache_t *buf_cache; + +static void +buf_fini(void) +{ + int i; + + kmem_free(buf_hash_table.ht_table, + (buf_hash_table.ht_mask + 1) * sizeof (void *)); + 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_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); + cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); + refcount_create(&hdr->b_l1hdr.b_refcnt); + mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); + multilist_link_init(&hdr->b_l1hdr.b_arc_node); + arc_space_consume(HDR_FULL_SIZE, 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); + 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_l2only_dest(void *vbuf, void *unused) +{ + arc_buf_hdr_t *hdr = 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); +} + +/* + * Reclaim callback -- invoked when memory is low. + */ +/* ARGSUSED */ +static void +hdr_recl(void *unused) +{ + dprintf("hdr_recl called\n"); + /* + * umem calls the reclaim func when we destroy the buf cache, + * which is after we do arc_fini(). + */ + if (arc_initialized) + zthr_wakeup(arc_reap_zthr); +} + +static void +buf_init(void) +{ + uint64_t *ct; + 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 < (uint64_t)physmem * PAGESIZE) + hsize <<= 1; +retry: + buf_hash_table.ht_mask = hsize - 1; + buf_hash_table.ht_table = + kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); + 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, hdr_recl, NULL, NULL, 0); + hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", + HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, + 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); + } +} + +/* + * 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. + */ +int32_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)); +} + +int32_t +arc_buf_lsize(arc_buf_t *buf) +{ + return (HDR_GET_LSIZE(buf->b_hdr)); +} + +enum zio_compress +arc_get_compression(arc_buf_t *buf) +{ + return (ARC_BUF_COMPRESSED(buf) ? + HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF); +} + +#define ARC_MINTIME (hz>>4) /* 62 ms */ + +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. + */ +static boolean_t +arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *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)) { + ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || + arc_hdr_has_uncompressed_buf(hdr)); + 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); +} + +static boolean_t +arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) +{ + enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); + boolean_t valid_cksum; + + ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); + VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); + + /* + * We rely on the blkptr's checksum to determine if the block + * is valid or not. When compressed arc is enabled, the l2arc + * writes the block to the l2arc just as it appears in the pool. + * This allows us to use the blkptr's checksum to validate the + * data that we just read off of the l2arc without having to store + * a separate checksum in the arc_buf_hdr_t. However, if compressed + * arc is disabled, then the data written to the l2arc is always + * uncompressed and won't match the block as it exists in the main + * pool. When this is the case, we must first compress it if it is + * compressed on the main pool before we can validate the checksum. + */ + if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { + ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); + uint64_t lsize = HDR_GET_LSIZE(hdr); + uint64_t csize; + + abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE); + csize = zio_compress_data(compress, zio->io_abd, + abd_to_buf(cdata), lsize); + + ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); + if (csize < HDR_GET_PSIZE(hdr)) { + /* + * Compressed blocks are always a multiple of the + * smallest ashift in the pool. Ideally, we would + * like to round up the csize to the next + * spa_min_ashift but that value may have changed + * since the block was last written. Instead, + * we rely on the fact that the hdr's psize + * was set to the psize of the block when it was + * last written. We set the csize to that value + * and zero out any part that should not contain + * data. + */ + abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize); + csize = HDR_GET_PSIZE(hdr); + } + zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL); + } + + /* + * 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. + */ + valid_cksum = (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); + zio_pop_transforms(zio); + return (valid_cksum); +} + +/* + * 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) { + ASSERT(arc_hdr_has_uncompressed_buf(hdr)); + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); + return; + } else if (ARC_BUF_COMPRESSED(buf)) { + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); + return; + } + + 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); +#ifdef illumos + arc_buf_watch(buf); +#endif +} + +#ifdef illumos +#ifndef _KERNEL +typedef struct procctl { + long cmd; + prwatch_t prwatch; +} procctl_t; +#endif + +/* ARGSUSED */ +static void +arc_buf_unwatch(arc_buf_t *buf) +{ +#ifndef _KERNEL + if (arc_watch) { + int result; + procctl_t ctl; + ctl.cmd = PCWATCH; + ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; + ctl.prwatch.pr_size = 0; + ctl.prwatch.pr_wflags = 0; + result = write(arc_procfd, &ctl, sizeof (ctl)); + ASSERT3U(result, ==, sizeof (ctl)); + } +#endif +} + +/* ARGSUSED */ +static void +arc_buf_watch(arc_buf_t *buf) +{ +#ifndef _KERNEL + if (arc_watch) { + int result; + procctl_t ctl; + ctl.cmd = PCWATCH; + ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; + ctl.prwatch.pr_size = arc_buf_size(buf); + ctl.prwatch.pr_wflags = WA_WRITE; + result = write(arc_procfd, &ctl, sizeof (ctl)); + ASSERT3U(result, ==, sizeof (ctl)); + } +#endif +} +#endif /* illumos */ + +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 or + * allocate b_thawed. + */ + if (ARC_BUF_COMPRESSED(buf)) { + ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || + arc_hdr_has_uncompressed_buf(hdr)); + return; + } + + ASSERT(HDR_HAS_L1HDR(hdr)); + arc_cksum_free(hdr); + + mutex_enter(&hdr->b_l1hdr.b_freeze_lock); +#ifdef ZFS_DEBUG + if (zfs_flags & ZFS_DEBUG_MODIFY) { + if (hdr->b_l1hdr.b_thawed != NULL) + kmem_free(hdr->b_l1hdr.b_thawed, 1); + hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); + } +#endif + + mutex_exit(&hdr->b_l1hdr.b_freeze_lock); + +#ifdef illumos + arc_buf_unwatch(buf); +#endif +} + +void +arc_buf_freeze(arc_buf_t *buf) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + kmutex_t *hash_lock; + + if (!(zfs_flags & ZFS_DEBUG_MODIFY)) + return; + + if (ARC_BUF_COMPRESSED(buf)) { + ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || + arc_hdr_has_uncompressed_buf(hdr)); + return; + } + + hash_lock = HDR_LOCK(hdr); + mutex_enter(hash_lock); + + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || + hdr->b_l1hdr.b_state == arc_anon); + arc_cksum_compute(buf); + mutex_exit(hash_lock); +} + +/* + * 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(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); + hdr->b_flags |= flags; +} + +static inline void +arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) +{ + ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(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(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); + + /* + * Holes and embedded blocks will always have a psize = 0 so + * we ignore the compression of the blkptr and set the + * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. + * Holes and embedded blocks remain anonymous so we don't + * 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); + HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); + ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); + ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); + } else { + arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); + HDR_SET_COMPRESS(hdr, cmp); + ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); + ASSERT(HDR_COMPRESSION_ENABLED(hdr)); + } +} + +/* + * 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. + */ + EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL); + + return (copied); +} + +/* + * 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, boolean_t compressed) +{ + arc_buf_hdr_t *hdr = buf->b_hdr; + boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); + dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; + + ASSERT3P(buf->b_data, !=, NULL); + IMPLY(compressed, hdr_compressed); + IMPLY(compressed, ARC_BUF_COMPRESSED(buf)); + + 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 it's 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) */ + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL); + return (0); + } else { + int error = zio_decompress_data(HDR_GET_COMPRESS(hdr), + hdr->b_l1hdr.b_pabd, buf->b_data, + HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); + + /* + * 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 %p, compress %d, psize %d, lsize %d", + hdr, HDR_GET_COMPRESS(hdr), + HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); + return (SET_ERROR(EIO)); + } + } + } + + /* 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); +} + +int +arc_decompress(arc_buf_t *buf) +{ + return (arc_buf_fill(buf, B_FALSE)); +} + +/* + * 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 (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); +} + +/* + * 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); + (void) 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) refcount_add_many(&state->arcs_esize[type], + arc_hdr_size(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) 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); + (void) 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) refcount_remove_many(&state->arcs_esize[type], + arc_hdr_size(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) 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) +{ + ASSERT(HDR_HAS_L1HDR(hdr)); + if (!MUTEX_HELD(HDR_LOCK(hdr))) { + ASSERT(hdr->b_l1hdr.b_state == arc_anon); + ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + } + + arc_state_t *state = hdr->b_l1hdr.b_state; + + if ((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 = 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 = 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 = refcount_count(&hdr->b_l1hdr.b_refcnt); + bufcnt = hdr->b_l1hdr.b_bufcnt; + update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL); + } 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) refcount_add_many(&new_state->arcs_size, + HDR_GET_LSIZE(hdr), hdr); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + } 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) refcount_add_many(&new_state->arcs_size, + arc_buf_size(buf), buf); + } + ASSERT3U(bufcnt, ==, buffers); + + if (hdr->b_l1hdr.b_pabd != NULL) { + (void) refcount_add_many(&new_state->arcs_size, + arc_hdr_size(hdr), hdr); + } else { + ASSERT(GHOST_STATE(old_state)); + } + } + } + + 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); + + /* + * 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) 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) refcount_remove_many( + &old_state->arcs_size, arc_buf_size(buf), + buf); + } + ASSERT3U(bufcnt, ==, buffers); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + (void) refcount_remove_many( + &old_state->arcs_size, arc_hdr_size(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) { + 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; + } + + if (type != ARC_SPACE_DATA) + 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) { + 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; + } + + if (type != ARC_SPACE_DATA) { + 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 hdr's compression matches the buf's compression + * 2. the hdr doesn't need to be byteswapped + * 3. the hdr isn't already being shared + * 4. the buf is either compressed or it is the last buf in the hdr list + * + * Criterion #4 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 sharable, 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 = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF; + boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0; + return (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, void *tag, boolean_t compressed, + boolean_t fill, arc_buf_t **ret) +{ + arc_buf_t *buf; + + 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); + + 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(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); + + /* + * Only honor requests for compressed bufs if the hdr is actually + * compressed. + */ + if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) + buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; + + /* + * 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. + */ + boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) && + abd_is_linear(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 the user wants the data from the hdr, we need to either copy or + * decompress the data. + */ + if (fill) { + return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0)); + } + + 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) +{ + arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag, + psize, lsize, compression_type); + + arc_loaned_bytes_update(arc_buf_size(buf)); + + 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) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); + (void) 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) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); + (void) 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) +{ + arc_state_t *state = hdr->b_l1hdr.b_state; + arc_buf_contents_t type = arc_buf_type(hdr); + uint64_t size = arc_hdr_size(hdr); + + /* protected by hash lock, if in the hash table */ + if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { + ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT(state != arc_anon && state != arc_l2c_only); + + (void) refcount_remove_many(&state->arcs_esize[type], + size, hdr); + } + (void) 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); + } + + 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) +{ + arc_state_t *state = hdr->b_l1hdr.b_state; + + ASSERT(arc_can_share(hdr, buf)); + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(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. + */ + refcount_transfer_ownership(&state->arcs_size, 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) +{ + arc_state_t *state = hdr->b_l1hdr.b_state; + + ASSERT(arc_buf_is_shared(buf)); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); + + /* + * We are no longer sharing this buffer so we need + * to transfer its ownership to the rightful owner. + */ + refcount_transfer_ownership(&state->arcs_size, 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(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(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 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(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); + + arc_cksum_verify(buf); +#ifdef illumos + arc_buf_unwatch(buf); +#endif + + 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; + } + + 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. + */ + if (lastbuf != NULL) { + /* 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_pabd(hdr); + + /* + * 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) || + 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_pabd(arc_buf_hdr_t *hdr) +{ + ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(!HDR_SHARED_DATA(hdr)); + + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr); + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + + ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); + ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); +} + +static void +arc_hdr_free_pabd(arc_buf_hdr_t *hdr) +{ + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + + /* + * 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); + ARCSTAT_BUMP(arcstat_l2_free_on_write); + } else { + arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, + arc_hdr_size(hdr), hdr); + } + hdr->b_l1hdr.b_pabd = NULL; + hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; + + ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); + 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, + enum zio_compress compression_type, arc_buf_contents_t type) +{ + arc_buf_hdr_t *hdr; + + VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); + + hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); + ASSERT(HDR_EMPTY(hdr)); + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); + ASSERT3P(hdr->b_l1hdr.b_thawed, ==, 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_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_pabd(hdr); + ASSERT(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)); + + 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) { + 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); + } 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); + +#ifdef ZFS_DEBUG + if (hdr->b_l1hdr.b_thawed != NULL) { + kmem_free(hdr->b_l1hdr.b_thawed, 1); + hdr->b_l1hdr.b_thawed = NULL; + } +#endif + + 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) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); + (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr); + + buf_discard_identity(hdr); + kmem_cache_free(old, hdr); + + return (nhdr); +} + +/* + * 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, + ZIO_COMPRESS_OFF, type); + ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); + + arc_buf_t *buf = NULL; + VERIFY0(arc_buf_alloc_impl(hdr, tag, 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) +{ + ASSERT3U(lsize, >, 0); + ASSERT3U(lsize, >=, psize); + ASSERT(compression_type > ZIO_COMPRESS_OFF); + ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS); + + arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, + compression_type, ARC_BUFC_DATA); + ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); + + arc_buf_t *buf = NULL; + VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, 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_decompress() 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. + */ + ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd)); + arc_hdr_free_pabd(hdr); + arc_share_buf(hdr, buf); + } + + 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 = arc_hdr_size(hdr); + + 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, -psize, 0, 0); + + (void) refcount_remove_many(&dev->l2ad_alloc, psize, 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(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_EMPTY(hdr)) + buf_discard_identity(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)) { + l2arc_trim(hdr); + arc_hdr_l2hdr_destroy(hdr); + } + + if (!buflist_held) + mutex_exit(&dev->l2ad_mtx); + } + + 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); + +#ifdef ZFS_DEBUG + if (hdr->b_l1hdr.b_thawed != NULL) { + kmem_free(hdr->b_l1hdr.b_thawed, 1); + hdr->b_l1hdr.b_thawed = NULL; + } +#endif + + if (hdr->b_l1hdr.b_pabd != NULL) { + arc_hdr_free_pabd(hdr); + } + } + + 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); + kmem_cache_free(hdr_full_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; + kmutex_t *hash_lock = HDR_LOCK(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; + } + + 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) ? + zfs_arc_min_prescient_prefetch_ms : zfs_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 it's 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); + + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + if (HDR_HAS_L2HDR(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 < min_lifetime * hz)) { + ARCSTAT_BUMP(arcstat_evict_skip); + return (bytes_evicted); + } + + ASSERT0(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(). + */ + arc_hdr_free_pabd(hdr); + + 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 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++; + + /* + * If arc_size isn't overflowing, signal any + * threads that might happen to be waiting. + * + * For each header evicted, we wake up a single + * thread. If we used cv_broadcast, we could + * wake up "too many" threads causing arc_size + * to significantly overflow arc_c; since + * arc_get_data_impl() doesn't check for overflow + * when it's woken up (it doesn't because it's + * possible for the ARC to be overflowing while + * full of un-evictable buffers, and the + * function should proceed in this case). + * + * If threads are left sleeping, due to not + * using cv_broadcast here, they will be woken + * up via cv_broadcast in arc_adjust_cb() just + * before arc_adjust_zthr sleeps. + */ + mutex_enter(&arc_adjust_lock); + if (!arc_is_overflowing()) + cv_signal(&arc_adjust_waiters_cv); + mutex_exit(&arc_adjust_lock); + } else { + ARCSTAT_BUMP(arcstat_mutex_miss); + } + } + + multilist_sublist_unlock(mls); + + 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++) { + 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_adjust_type() and + * arc_evict_state_impl(). + */ + markers[i]->b_spa = 0; + + multilist_sublist_t *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_limit) > 0) { + arc_prune_async((aggsum_upper_bound(&astat_dnode_size) - + arc_dnode_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 (refcount_count(&state->arcs_esize[type]) != 0) { + evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); + + if (!retry) + break; + } + + return (evicted); +} + +/* + * Helper function for arc_prune_async() it is responsible for safely + * handling the execution of a registered arc_prune_func_t. + */ +static void +arc_prune_task(void *ptr) +{ + arc_prune_t *ap = (arc_prune_t *)ptr; + arc_prune_func_t *func = ap->p_pfunc; + + if (func != NULL) + func(ap->p_adjust, ap->p_private); + + refcount_remove(&ap->p_refcnt, func); +} + +/* + * Notify registered consumers they must drop holds on a portion of the ARC + * buffered they reference. This provides a mechanism to ensure the ARC can + * honor the arc_meta_limit and reclaim otherwise pinned ARC buffers. This + * is analogous to dnlc_reduce_cache() but more generic. + * + * This operation is performed asynchronously so it may be safely called + * in the context of the arc_reclaim_thread(). A reference is taken here + * for each registered arc_prune_t and the arc_prune_task() is responsible + * for releasing it once the registered arc_prune_func_t has completed. + */ +static void +arc_prune_async(int64_t adjust) +{ + arc_prune_t *ap; + + mutex_enter(&arc_prune_mtx); + for (ap = list_head(&arc_prune_list); ap != NULL; + ap = list_next(&arc_prune_list, ap)) { + + if (refcount_count(&ap->p_refcnt) >= 2) + continue; + + refcount_add(&ap->p_refcnt, ap->p_pfunc); + ap->p_adjust = adjust; + if (taskq_dispatch(arc_prune_taskq, arc_prune_task, + ap, TQ_SLEEP) == TASKQID_INVALID) { + refcount_remove(&ap->p_refcnt, ap->p_pfunc); + continue; + } + ARCSTAT_BUMP(arcstat_prune); + } + mutex_exit(&arc_prune_mtx); +} + +/* + * 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_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, + arc_buf_contents_t type) +{ + int64_t delta; + + if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) { + delta = MIN(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_adjust_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_adjust 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 && refcount_count(&arc_mru->arcs_esize[type]) > 0) { + delta = MIN(refcount_count(&arc_mru->arcs_esize[type]), + adjustmnt); + total_evicted += arc_adjust_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 && refcount_count(&arc_mfu->arcs_esize[type]) > 0) { + delta = MIN(refcount_count(&arc_mfu->arcs_esize[type]), + adjustmnt); + total_evicted += arc_adjust_impl(arc_mfu, 0, delta, type); + } + + adjustmnt = meta_used - arc_meta_limit; + + if (adjustmnt > 0 && + refcount_count(&arc_mru_ghost->arcs_esize[type]) > 0) { + delta = MIN(adjustmnt, + refcount_count(&arc_mru_ghost->arcs_esize[type])); + total_evicted += arc_adjust_impl(arc_mru_ghost, 0, delta, type); + adjustmnt -= delta; + } + + if (adjustmnt > 0 && + refcount_count(&arc_mfu_ghost->arcs_esize[type]) > 0) { + delta = MIN(adjustmnt, + refcount_count(&arc_mfu_ghost->arcs_esize[type])); + total_evicted += arc_adjust_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_adjust_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)(refcount_count(&arc_anon->arcs_size) + + refcount_count(&arc_mru->arcs_size) - arc_p)); + + total_evicted += arc_adjust_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)(refcount_count(&arc_mfu->arcs_size) - + (arc_c - arc_p))); + + total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); + + return (total_evicted); +} + +static uint64_t +arc_adjust_meta(uint64_t meta_used) +{ + if (zfs_arc_meta_strategy == ARC_STRATEGY_META_ONLY) + return (arc_adjust_meta_only(meta_used)); + else + return (arc_adjust_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_adjust_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_adjust(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_adjust_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)(refcount_count(&arc_anon->arcs_size) + + 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_adjust_type(arc_mru) == ARC_BUFC_METADATA && + ameta > arc_meta_min) { + bytes = arc_adjust_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_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); + } else { + bytes = arc_adjust_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_adjust_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_adjust_type(arc_mfu) == ARC_BUFC_METADATA && + ameta > arc_meta_min) { + bytes = arc_adjust_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_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); + } else { + bytes = arc_adjust_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_adjust_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 = refcount_count(&arc_mru->arcs_size) + + refcount_count(&arc_mru_ghost->arcs_size) - arc_c; + + bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); + total_evicted += bytes; + + target -= bytes; + + total_evicted += + arc_adjust_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 = refcount_count(&arc_mru_ghost->arcs_size) + + refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; + + bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); + total_evicted += bytes; + + target -= bytes; + + total_evicted += + arc_adjust_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); +} + +static void +arc_reduce_target_size(int64_t to_free) +{ + uint64_t asize = aggsum_value(&arc_size); + if (arc_c > arc_c_min) { + DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, + arc_c_min, uint64_t, arc_p, uint64_t, to_free); + if (arc_c > arc_c_min + to_free) + atomic_add_64(&arc_c, -to_free); + else + arc_c = arc_c_min; + + atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); + if (asize < arc_c) + arc_c = MAX(asize, arc_c_min); + if (arc_p > arc_c) + arc_p = (arc_c >> 1); + + DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, + arc_p); + + ASSERT(arc_c >= arc_c_min); + ASSERT((int64_t)arc_p >= 0); + } + + if (asize > arc_c) { + DTRACE_PROBE2(arc__shrink_adjust, uint64_t, asize, + uint64_t, arc_c); + /* See comment in arc_adjust_cb_check() on why lock+flag */ + mutex_enter(&arc_adjust_lock); + arc_adjust_needed = B_TRUE; + mutex_exit(&arc_adjust_lock); + zthr_wakeup(arc_adjust_zthr); + } +} + +typedef enum free_memory_reason_t { + FMR_UNKNOWN, + FMR_NEEDFREE, + FMR_LOTSFREE, + FMR_SWAPFS_MINFREE, + FMR_PAGES_PP_MAXIMUM, + FMR_HEAP_ARENA, + FMR_ZIO_ARENA, +} free_memory_reason_t; + +int64_t last_free_memory; +free_memory_reason_t last_free_reason; + +/* + * Additional reserve of pages for pp_reserve. + */ +int64_t arc_pages_pp_reserve = 64; + +/* + * Additional reserve of pages for swapfs. + */ +int64_t arc_swapfs_reserve = 64; + +/* + * Return the amount of memory that can be consumed before reclaim will be + * needed. Positive if there is sufficient free memory, negative indicates + * the amount of memory that needs to be freed up. + */ +static int64_t +arc_available_memory(void) +{ + int64_t lowest = INT64_MAX; + int64_t n; + free_memory_reason_t r = FMR_UNKNOWN; + +#ifdef _KERNEL +#ifdef __FreeBSD__ + /* + * Cooperate with pagedaemon when it's time for it to scan + * and reclaim some pages. + */ + n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); + if (n < lowest) { + lowest = n; + r = FMR_LOTSFREE; + } + +#else + if (needfree > 0) { + n = PAGESIZE * (-needfree); + if (n < lowest) { + lowest = n; + r = FMR_NEEDFREE; + } + } + + /* + * check that we're out of range of the pageout scanner. It starts to + * schedule paging if freemem is less than lotsfree and needfree. + * lotsfree is the high-water mark for pageout, and needfree is the + * number of needed free pages. We add extra pages here to make sure + * the scanner doesn't start up while we're freeing memory. + */ + n = PAGESIZE * (freemem - lotsfree - needfree - desfree); + if (n < lowest) { + lowest = n; + r = FMR_LOTSFREE; + } + + /* + * check to make sure that swapfs has enough space so that anon + * reservations can still succeed. anon_resvmem() checks that the + * availrmem is greater than swapfs_minfree, and the number of reserved + * swap pages. We also add a bit of extra here just to prevent + * circumstances from getting really dire. + */ + n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - + desfree - arc_swapfs_reserve); + if (n < lowest) { + lowest = n; + r = FMR_SWAPFS_MINFREE; + } + + + /* + * Check that we have enough availrmem that memory locking (e.g., via + * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum + * stores the number of pages that cannot be locked; when availrmem + * drops below pages_pp_maximum, page locking mechanisms such as + * page_pp_lock() will fail.) + */ + n = PAGESIZE * (availrmem - pages_pp_maximum - + arc_pages_pp_reserve); + if (n < lowest) { + lowest = n; + r = FMR_PAGES_PP_MAXIMUM; + } + +#endif /* __FreeBSD__ */ +#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) + /* + * If we're on an i386 platform, it's possible that we'll exhaust the + * kernel heap space before we ever run out of available physical + * memory. Most checks of the size of the heap_area compare against + * tune.t_minarmem, which is the minimum available real memory that we + * can have in the system. However, this is generally fixed at 25 pages + * which is so low that it's useless. In this comparison, we seek to + * calculate the total heap-size, and reclaim if more than 3/4ths of the + * heap is allocated. (Or, in the calculation, if less than 1/4th is + * free) + */ + n = uma_avail() - (long)(uma_limit() / 4); + if (n < lowest) { + lowest = n; + r = FMR_HEAP_ARENA; + } +#endif + + /* + * If zio data pages are being allocated out of a separate heap segment, + * then enforce that the size of available vmem for this arena remains + * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free. + * + * Note that reducing the arc_zio_arena_free_shift keeps more virtual + * memory (in the zio_arena) free, which can avoid memory + * fragmentation issues. + */ + if (zio_arena != NULL) { + n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - + (vmem_size(zio_arena, VMEM_ALLOC) >> + arc_zio_arena_free_shift); + if (n < lowest) { + lowest = n; + r = FMR_ZIO_ARENA; + } + } + +#else /* _KERNEL */ + /* Every 100 calls, free a small amount */ + if (spa_get_random(100) == 0) + lowest = -1024; +#endif /* _KERNEL */ + + last_free_memory = lowest; + last_free_reason = r; + DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); + return (lowest); +} + + +/* + * 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. + */ +static boolean_t +arc_reclaim_needed(void) +{ + return (arc_available_memory() < 0); +} + +extern kmem_cache_t *zio_buf_cache[]; +extern kmem_cache_t *zio_data_buf_cache[]; +extern kmem_cache_t *range_seg_cache; +extern kmem_cache_t *abd_chunk_cache; + +static __noinline void +arc_kmem_reap_soon(void) +{ + size_t i; + kmem_cache_t *prev_cache = NULL; + kmem_cache_t *prev_data_cache = NULL; + + DTRACE_PROBE(arc__kmem_reap_start); +#ifdef _KERNEL + if (aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) { + /* + * We are exceeding our meta-data cache limit. + * Purge some DNLC entries to release holds on meta-data. + */ + dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); + } +#if defined(__i386) + /* + * Reclaim unused memory from all kmem caches. + */ + kmem_reap(); +#endif +#endif + + for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { + if (zio_buf_cache[i] != prev_cache) { + prev_cache = zio_buf_cache[i]; + kmem_cache_reap_soon(zio_buf_cache[i]); + } + if (zio_data_buf_cache[i] != prev_data_cache) { + prev_data_cache = zio_data_buf_cache[i]; + kmem_cache_reap_soon(zio_data_buf_cache[i]); + } + } + kmem_cache_reap_soon(abd_chunk_cache); + kmem_cache_reap_soon(buf_cache); + kmem_cache_reap_soon(hdr_full_cache); + kmem_cache_reap_soon(hdr_l2only_cache); + kmem_cache_reap_soon(range_seg_cache); + +#ifdef illumos + if (zio_arena != NULL) { + /* + * Ask the vmem arena to reclaim unused memory from its + * quantum caches. + */ + vmem_qcache_reap(zio_arena); + } +#endif + DTRACE_PROBE(arc__kmem_reap_end); +} + +/* ARGSUSED */ +static boolean_t +arc_adjust_cb_check(void *arg, zthr_t *zthr) +{ + /* + * This is necessary in order for the mdb ::arc dcmd to + * show up to date information. Since the ::arc command + * does not call the kstat's update function, without + * this call, the command 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_adjust_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_get_data_impl() to tell us when to adjust, + * rather than checking if we are overflowing here, so that we are + * sure to not leave arc_get_data_impl() waiting on + * arc_adjust_waiters_cv. If we have become "not overflowing" since + * arc_get_data_impl() checked, we need to wake it up. We could + * broadcast the CV here, but arc_get_data_impl() may have not yet + * gone to sleep. We would need to use a mutex to ensure that this + * function doesn't broadcast until arc_get_data_impl() has gone to + * sleep (e.g. the arc_adjust_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_get_data_impl() when it calls zthr_wakeup(). + */ + return (arc_adjust_needed); +} + +/* + * Keep arc_size under arc_c by running arc_adjust which evicts data + * from the ARC. */ +/* ARGSUSED */ +static int +arc_adjust_cb(void *arg, zthr_t *zthr) +{ + uint64_t evicted = 0; + + /* Evict from cache */ + evicted = arc_adjust(); + + /* + * If evicted is zero, we couldn't evict anything + * via arc_adjust(). 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 adjust waiters. + */ + mutex_enter(&arc_adjust_lock); + arc_adjust_needed = !zthr_iscancelled(arc_adjust_zthr) && + evicted > 0 && aggsum_compare(&arc_size, arc_c) > 0; + if (!arc_adjust_needed) { + /* + * We're either no longer overflowing, or we + * can't evict anything more, so we should wake + * up any waiters. + */ + cv_broadcast(&arc_adjust_waiters_cv); + } + mutex_exit(&arc_adjust_lock); + + return (0); +} + +/* 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 60) 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_adjust_cb() + * to free more buffers. + */ +/* ARGSUSED */ +static int +arc_reap_cb(void *arg, zthr_t *zthr) +{ + int64_t free_memory; + + /* + * 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) { +#ifdef _KERNEL +#ifdef illumos + to_free = MAX(to_free, ptob(needfree)); +#endif +#endif + arc_reduce_target_size(to_free); + } + + return (0); +} + +static u_int arc_dnlc_evicts_arg; +extern struct vfsops zfs_vfsops; + +static void +arc_dnlc_evicts_thread(void *dummy __unused) +{ + callb_cpr_t cpr; + u_int percent; + + CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG); + + mutex_enter(&arc_dnlc_evicts_lock); + while (!arc_dnlc_evicts_thread_exit) { + CALLB_CPR_SAFE_BEGIN(&cpr); + (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); + CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock); + if (arc_dnlc_evicts_arg != 0) { + percent = arc_dnlc_evicts_arg; + mutex_exit(&arc_dnlc_evicts_lock); +#ifdef _KERNEL + vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops); +#endif + mutex_enter(&arc_dnlc_evicts_lock); + /* + * Clear our token only after vnlru_free() + * pass is done, to avoid false queueing of + * the requests. + */ + arc_dnlc_evicts_arg = 0; + } + } + arc_dnlc_evicts_thread_exit = FALSE; + cv_broadcast(&arc_dnlc_evicts_cv); + CALLB_CPR_EXIT(&cpr); + thread_exit(); +} + +void +dnlc_reduce_cache(void *arg) +{ + u_int percent; + + percent = (u_int)(uintptr_t)arg; + mutex_enter(&arc_dnlc_evicts_lock); + if (arc_dnlc_evicts_arg == 0) { + arc_dnlc_evicts_arg = percent; + cv_broadcast(&arc_dnlc_evicts_cv); + } + mutex_exit(&arc_dnlc_evicts_lock); +} + +/* + * Adapt arc info given the number of bytes we are trying to add and + * the state that we are comming 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 = refcount_count(&arc_mru_ghost->arcs_size); + int64_t mfug_size = 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); + 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); + 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 + */ + if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) > + 0) { + DTRACE_PROBE1(arc__inc_adapt, int, bytes); + 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. + */ +static boolean_t +arc_is_overflowing(void) +{ + /* Always allow at least one block of overflow */ + uint64_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) >= arc_c + overflow); +} + +static abd_t * +arc_get_data_abd(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); + 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); + if (type == ARC_BUFC_METADATA) { + return (zio_buf_alloc(size)); + } else { + ASSERT(type == ARC_BUFC_DATA); + return (zio_data_buf_alloc(size)); + } +} + +/* + * 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) +{ + arc_state_t *state = hdr->b_l1hdr.b_state; + arc_buf_contents_t type = arc_buf_type(hdr); + + arc_adapt(size, state); + + /* + * If arc_size is currently overflowing, and has grown past our + * upper limit, we must be adding data faster than the evict + * thread can evict. Thus, 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 halt and wait for the + * eviction thread to catch up. + * + * It's also possible that the reclaim thread is unable to evict + * enough buffers to get arc_size below the overflow limit (e.g. + * due to buffers being un-evictable, or hash lock collisions). + * In this case, we want to proceed regardless if we're + * overflowing; thus we don't use a while loop here. + */ + if (arc_is_overflowing()) { + mutex_enter(&arc_adjust_lock); + + /* + * Now that we've acquired the lock, we may no longer be + * over the overflow limit, lets check. + * + * We're ignoring the case of spurious wake ups. If that + * were to happen, it'd let this thread consume an ARC + * buffer before it should have (i.e. before we're under + * the overflow limit and were signalled by the reclaim + * thread). As long as that is a rare occurrence, it + * shouldn't cause any harm. + */ + if (arc_is_overflowing()) { + arc_adjust_needed = B_TRUE; + zthr_wakeup(arc_adjust_zthr); + (void) cv_wait(&arc_adjust_waiters_cv, + &arc_adjust_lock); + } + mutex_exit(&arc_adjust_lock); + } + + 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) 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(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + (void) 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_compare(&arc_size, arc_c) < 0 && + hdr->b_l1hdr.b_state == arc_anon && + (refcount_count(&arc_anon->arcs_size) + + refcount_count(&arc_mru->arcs_size) > arc_p)) + arc_p = MIN(arc_c, arc_p + size); + } + ARCSTAT_BUMP(arcstat_allocated); +} + +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(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT(state != arc_anon && state != arc_l2c_only); + + (void) refcount_remove_many(&state->arcs_esize[type], + size, tag); + } + (void) 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 (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); + 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 (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 (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 { + ASSERT(!"invalid arc 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); + ARCSTAT_BUMP(arcstat_access_skip); + 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), + 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(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); + } else { + if (HDR_COMPRESSION_ENABLED(hdr)) { + ASSERT3U(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)); + } +} + +static void +arc_read_done(zio_t *zio) +{ + 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; + boolean_t no_zio_error = (zio->io_error == 0); + + /* + * 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)) { + 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]); + + arc_buf_hdr_t *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 (no_zio_error) { + /* 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; + } + } + + 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 && no_zio_error && 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 (no_zio_error) { + int error = arc_buf_alloc_impl(hdr, acb->acb_private, + acb->acb_compressed, zio->io_error == 0, + &acb->acb_buf); + if (error != 0) { + /* + * Decompression 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_PREFETCH(hdr)); + ASSERT0(hdr->b_l1hdr.b_bufcnt); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + } + + ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || + callback_list != NULL); + + if (no_zio_error) { + 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 = 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 = 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) != 0; + int rc = 0; + + ASSERT(!BP_IS_EMBEDDED(bp) || + BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); + +top: + if (!BP_IS_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); + } + + if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) { + 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; + + 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; + 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); + return (0); + } + mutex_exit(hash_lock); + return (0); + } + + 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(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); + /* Get a buf with the desired data in it. */ + rc = arc_buf_alloc_impl(hdr, private, + compressed_read, B_TRUE, &buf); + if (rc != 0) { + arc_buf_destroy(buf, private); + buf = NULL; + } + ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) || + rc == 0 || rc != ENOENT); + } else if (*arc_flags & ARC_FLAG_PREFETCH && + 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; + + if (hdr == NULL) { + /* this block is not in the cache */ + 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_GET_COMPRESS(bp), type); + + if (!BP_IS_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. 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); + } + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); + ASSERT(!HDR_IO_IN_PROGRESS(hdr)); + ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); + ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); + ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); + + /* + * This is a delicate dance that we play here. + * This hdr is 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_access(hdr, hash_lock); + arc_hdr_alloc_pabd(hdr); + } + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + size = arc_hdr_size(hdr); + + /* + * If compression is enabled on the hdr, then will do + * RAW I/O and will store the compressed data in the hdr's + * data block. Otherwise, the hdr's data block will contain + * the uncompressed data. + */ + if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { + zio_flags |= ZIO_FLAG_RAW; + } + + if (*arc_flags & ARC_FLAG_PREFETCH) + 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_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; + + 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. Try again in + * L2ARC if possible. + */ + ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); + + 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); +#ifdef _KERNEL +#ifdef RACCT + if (racct_enable) { + PROC_LOCK(curproc); + racct_add_force(curproc, RACCT_READBPS, size); + racct_add_force(curproc, RACCT_READIOPS, 1); + PROC_UNLOCK(curproc); + } +#endif /* RACCT */ + curthread->td_ru.ru_inblock++; +#endif + + 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; + + 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->b_l1hdr.b_pabd; + } + + 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(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, size); + + if (*arc_flags & ARC_FLAG_NOWAIT) { + zio_nowait(rzio); + return (0); + } + + ASSERT(*arc_flags & ARC_FLAG_WAIT); + if (zio_wait(rzio) == 0) + return (0); + + /* 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); + if (l2arc_ndev != 0) { + DTRACE_PROBE1(l2arc__miss, + arc_buf_hdr_t *, hdr); + ARCSTAT_BUMP(arcstat_l2_misses); + } + } + + rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, 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) + return (zio_wait(rzio)); + + ASSERT(*arc_flags & ARC_FLAG_NOWAIT); + zio_nowait(rzio); + } + return (0); +} + +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); + refcount_create(&p->p_refcnt); + + mutex_enter(&arc_prune_mtx); + 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 (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(arc_prune_taskq); + ASSERT0(refcount_count(&p->p_refcnt)); + 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) && + 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 it's 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(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(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)) { + l2arc_trim(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); + enum zio_compress compress = 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)) { + 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_pabd(hdr); + 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) || + HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); + ASSERT(!ARC_BUF_SHARED(buf)); + } + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + ASSERT3P(state, !=, arc_l2c_only); + + (void) refcount_remove_many(&state->arcs_size, + arc_buf_size(buf), buf); + + if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { + ASSERT3P(state, !=, arc_l2c_only); + (void) refcount_remove_many(&state->arcs_esize[type], + arc_buf_size(buf), buf); + } + + hdr->b_l1hdr.b_bufcnt -= 1; + arc_cksum_verify(buf); +#ifdef illumos + arc_buf_unwatch(buf); +#endif + + 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, compress, type); + ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); + ASSERT0(nhdr->b_l1hdr.b_bufcnt); + ASSERT0(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; + (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); + buf->b_hdr = nhdr; + + mutex_exit(&buf->b_evict_lock); + (void) refcount_add_many(&arc_anon->arcs_size, + arc_buf_size(buf), buf); + } else { + mutex_exit(&buf->b_evict_lock); + ASSERT(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)); + 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 = (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; + uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); + + ASSERT(HDR_HAS_L1HDR(hdr)); + ASSERT(!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); +#ifdef illumos + arc_buf_unwatch(buf); +#endif + if (hdr->b_l1hdr.b_pabd != NULL) { + if (arc_buf_is_shared(buf)) { + arc_unshare_buf(hdr, buf); + } else { + arc_hdr_free_pabd(hdr); + } + } + } + ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); + 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_cksum_compute(buf); + arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); + + enum zio_compress compress; + if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { + compress = ZIO_COMPRESS_OFF; + } else { + ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); + compress = BP_GET_COMPRESS(zio->io_bp); + } + HDR_SET_PSIZE(hdr, psize); + arc_hdr_set_compress(hdr, compress); + + + /* + * Fill the hdr with data. 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 (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) { + arc_hdr_alloc_pabd(hdr); + + /* + * 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 (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { + ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=, + ZIO_COMPRESS_OFF); + ASSERT3U(psize, >, 0); + + abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize); + } else { + ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr)); + + 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); + } + + arc_hdr_verify(hdr, zio->io_bp); +} + +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(refcount_is_zero( + &exists->b_l1hdr.b_refcnt)); + arc_change_state(arc_anon, exists, hash_lock); + mutex_exit(hash_lock); + arc_hdr_destroy(exists); + 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(!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_COMPRESSED(buf)) { + /* + * We're writing a pre-compressed buffer. Make the + * compression algorithm requested by the zio_prop_t match + * the pre-compressed buffer's compression algorithm. + */ + localprop.zp_compress = HDR_GET_COMPRESS(hdr); + + ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf)); + zio_flags |= ZIO_FLAG_RAW; + } + 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_pabd(hdr); + } + VERIFY3P(buf->b_data, !=, NULL); + 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); +} + +static int +arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg) +{ +#ifdef _KERNEL + uint64_t available_memory = ptob(freemem); + +#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) + available_memory = MIN(available_memory, uma_avail()); +#endif + + if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) + return (0); + + if (txg > spa->spa_lowmem_last_txg) { + spa->spa_lowmem_last_txg = txg; + spa->spa_lowmem_page_load = 0; + } + /* + * If we are in pageout, we know that memory is already tight, + * the arc is already going to be evicting, so we just want to + * continue to let page writes occur as quickly as possible. + */ + if (curproc == pageproc) { + if (spa->spa_lowmem_page_load > + MAX(ptob(minfree), available_memory) / 4) + return (SET_ERROR(ERESTART)); + /* Note: reserve is inflated, so we deflate */ + atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8); + return (0); + } else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) { + /* memory is low, delay before restarting */ + ARCSTAT_INCR(arcstat_memory_throttle_count, 1); + return (SET_ERROR(EAGAIN)); + } + spa->spa_lowmem_page_load = 0; +#endif /* _KERNEL */ + return (0); +} + +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 (reserve > arc_c/4 && !arc_no_grow) { + arc_c = MIN(arc_c_max, reserve * 4); + DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); + } + if (reserve > arc_c) + return (SET_ERROR(ENOMEM)); + + /* + * 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)(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) { + uint64_t meta_esize = + refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); + uint64_t data_esize = + 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); + 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 = refcount_count(&state->arcs_size); + evict_data->value.ui64 = + refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); + evict_metadata->value.ui64 = + 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 (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_bonus_size) = aggsum_value(&astat_bonus_size); + ARCSTAT(arcstat_dnode_size) = aggsum_value(&astat_dnode_size); + ARCSTAT(arcstat_dbuf_size) = aggsum_value(&astat_dbuf_size); +#if defined(__FreeBSD__) && 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_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size); + } + + 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. + */ +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 it's lifetime + * (i.e. it's 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)); +} + +#ifdef _KERNEL +static eventhandler_tag arc_event_lowmem = NULL; + +static void +arc_lowmem(void *arg __unused, int howto __unused) +{ + int64_t free_memory, to_free; + + arc_no_grow = B_TRUE; + arc_warm = B_TRUE; + arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry); + free_memory = arc_available_memory(); + to_free = (arc_c >> arc_shrink_shift) - MIN(free_memory, 0); + DTRACE_PROBE2(arc__needfree, int64_t, free_memory, int64_t, to_free); + arc_reduce_target_size(to_free); + + mutex_enter(&arc_adjust_lock); + arc_adjust_needed = B_TRUE; + zthr_wakeup(arc_adjust_zthr); + + /* + * It is unsafe to block here in arbitrary threads, because we can come + * here from ARC itself and may hold ARC locks and thus risk a deadlock + * with ARC reclaim thread. + */ + if (curproc == pageproc) + (void) cv_wait(&arc_adjust_waiters_cv, &arc_adjust_lock); + mutex_exit(&arc_adjust_lock); +} +#endif + +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); + + refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); + refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); + refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); + refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); + refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); + refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); + refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); + refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); + refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); + refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); + refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); + refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); + + refcount_create(&arc_anon->arcs_size); + refcount_create(&arc_mru->arcs_size); + refcount_create(&arc_mru_ghost->arcs_size); + refcount_create(&arc_mfu->arcs_size); + refcount_create(&arc_mfu_ghost->arcs_size); + 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_bonus_size, 0); + aggsum_init(&astat_dnode_size, 0); + aggsum_init(&astat_dbuf_size, 0); + aggsum_init(&astat_l2_hdr_size, 0); +} + +static void +arc_state_fini(void) +{ + refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); + refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); + refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); + refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); + refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); + refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); + refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); + refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); + refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); + refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); + refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); + refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); + + refcount_destroy(&arc_anon->arcs_size); + refcount_destroy(&arc_mru->arcs_size); + refcount_destroy(&arc_mru_ghost->arcs_size); + refcount_destroy(&arc_mfu->arcs_size); + refcount_destroy(&arc_mfu_ghost->arcs_size); + 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]); + + 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_bonus_size); + aggsum_fini(&astat_dnode_size); + aggsum_fini(&astat_dbuf_size); + aggsum_fini(&astat_l2_hdr_size); +} + +uint64_t +arc_max_bytes(void) +{ + return (arc_c_max); +} + +void +arc_init(void) +{ + int i, prefetch_tunable_set = 0; + + /* + * allmem is "all memory that we could possibly use". + */ +#ifdef illumos +#ifdef _KERNEL + uint64_t allmem = ptob(physmem - swapfs_minfree); +#else + uint64_t allmem = (physmem * PAGESIZE) / 2; +#endif +#else + uint64_t allmem = kmem_size(); +#endif + mutex_init(&arc_adjust_lock, NULL, MUTEX_DEFAULT, NULL); + cv_init(&arc_adjust_waiters_cv, NULL, CV_DEFAULT, NULL); + + mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL); + cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL); + + /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ + arc_c_min = MAX(allmem / 32, arc_abs_min); + /* set max to 5/8 of all memory, or all but 1GB, whichever is more */ + if (allmem >= 1 << 30) + arc_c_max = allmem - (1 << 30); + else + arc_c_max = arc_c_min; + arc_c_max = MAX(allmem * 5 / 8, arc_c_max); + + /* + * 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. + */ +#ifndef _KERNEL + arc_c_min = arc_c_max / 2; +#endif + +#ifdef _KERNEL + /* + * Allow the tunables to override our calculations if they are + * reasonable. + */ + if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) { + arc_c_max = zfs_arc_max; + arc_c_min = MIN(arc_c_min, arc_c_max); + } + if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) + arc_c_min = zfs_arc_min; +#endif + + arc_c = arc_c_max; + arc_p = (arc_c >> 1); + + /* limit meta-data to 1/4 of the arc capacity */ + arc_meta_limit = arc_c_max / 4; + +#ifdef _KERNEL + /* + * Metadata is stored in the kernel's heap. Don't let us + * use more than half the heap for the ARC. + */ +#ifdef __FreeBSD__ + arc_meta_limit = MIN(arc_meta_limit, uma_limit() / 2); + arc_dnode_limit = arc_meta_limit / 10; +#else + arc_meta_limit = MIN(arc_meta_limit, + vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2); +#endif +#endif + + /* Allow the tunable to override if it is reasonable */ + if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) + arc_meta_limit = zfs_arc_meta_limit; + + if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) + arc_c_min = arc_meta_limit / 2; + + if (zfs_arc_meta_min > 0) { + arc_meta_min = zfs_arc_meta_min; + } else { + arc_meta_min = arc_c_min / 2; + } + + /* Valid range: <arc_meta_min> - <arc_c_max> */ + if ((zfs_arc_dnode_limit) && (zfs_arc_dnode_limit != arc_dnode_limit) && + (zfs_arc_dnode_limit >= zfs_arc_meta_min) && + (zfs_arc_dnode_limit <= arc_c_max)) + arc_dnode_limit = zfs_arc_dnode_limit; + + if (zfs_arc_grow_retry > 0) + arc_grow_retry = zfs_arc_grow_retry; + + if (zfs_arc_shrink_shift > 0) + arc_shrink_shift = zfs_arc_shrink_shift; + + if (zfs_arc_no_grow_shift > 0) + arc_no_grow_shift = zfs_arc_no_grow_shift; + /* + * Ensure that arc_no_grow_shift is less than arc_shrink_shift. + */ + if (arc_no_grow_shift >= arc_shrink_shift) + arc_no_grow_shift = arc_shrink_shift - 1; + + if (zfs_arc_p_min_shift > 0) + arc_p_min_shift = zfs_arc_p_min_shift; + + /* 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; + + zfs_arc_min = arc_c_min; + zfs_arc_max = arc_c_max; + + arc_state_init(); + + /* + * The arc must be "uninitialized", so that hdr_recl() (which is + * registered by buf_init()) will not access arc_reap_zthr before + * it is created. + */ + ASSERT(!arc_initialized); + 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", max_ncpus, minclsyspri, + max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC); + + arc_dnlc_evicts_thread_exit = FALSE; + + 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_adjust_zthr = zthr_create_timer(arc_adjust_cb_check, + arc_adjust_cb, NULL, SEC2NSEC(1)); + arc_reap_zthr = zthr_create_timer(arc_reap_cb_check, + arc_reap_cb, NULL, SEC2NSEC(1)); + +#ifdef _KERNEL + arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, + EVENTHANDLER_PRI_FIRST); +#endif + + (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0, + TS_RUN, minclsyspri); + + arc_initialized = B_TRUE; + arc_warm = B_FALSE; + + /* + * Calculate maximum amount of dirty data per pool. + * + * If it has been set by /etc/system, 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 4GB). + */ + if (zfs_dirty_data_max == 0) { + zfs_dirty_data_max = ptob(physmem) * + zfs_dirty_data_max_percent / 100; + zfs_dirty_data_max = MIN(zfs_dirty_data_max, + zfs_dirty_data_max_max); + } + +#ifdef _KERNEL + if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) + prefetch_tunable_set = 1; + +#ifdef __i386__ + if (prefetch_tunable_set == 0) { + printf("ZFS NOTICE: Prefetch is disabled by default on i386 " + "-- to enable,\n"); + printf(" add \"vfs.zfs.prefetch_disable=0\" " + "to /boot/loader.conf.\n"); + zfs_prefetch_disable = 1; + } +#else + if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && + prefetch_tunable_set == 0) { + printf("ZFS NOTICE: Prefetch is disabled by default if less " + "than 4GB of RAM is present;\n" + " to enable, add \"vfs.zfs.prefetch_disable=0\" " + "to /boot/loader.conf.\n"); + zfs_prefetch_disable = 1; + } +#endif + /* Warn about ZFS memory and address space requirements. */ + if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { + printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " + "expect unstable behavior.\n"); + } + if (allmem < 512 * (1 << 20)) { + printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " + "expect unstable behavior.\n"); + printf(" Consider tuning vm.kmem_size and " + "vm.kmem_size_max\n"); + printf(" in /boot/loader.conf.\n"); + } +#endif +} + +void +arc_fini(void) +{ + arc_prune_t *p; + +#ifdef _KERNEL + if (arc_event_lowmem != NULL) + EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); +#endif + + /* Use B_TRUE to ensure *all* buffers are evicted */ + arc_flush(NULL, B_TRUE); + + mutex_enter(&arc_dnlc_evicts_lock); + arc_dnlc_evicts_thread_exit = TRUE; + /* + * The user evicts thread will set arc_user_evicts_thread_exit + * to FALSE when it is finished exiting; we're waiting for that. + */ + while (arc_dnlc_evicts_thread_exit) { + cv_signal(&arc_dnlc_evicts_cv); + cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); + } + mutex_exit(&arc_dnlc_evicts_lock); + + arc_initialized = B_FALSE; + + 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); + refcount_remove(&p->p_refcnt, &arc_prune_list); + 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_adjust_zthr); + zthr_destroy(arc_adjust_zthr); + + mutex_destroy(&arc_dnlc_evicts_lock); + cv_destroy(&arc_dnlc_evicts_cv); + + (void) zthr_cancel(arc_reap_zthr); + zthr_destroy(arc_reap_zthr); + + mutex_destroy(&arc_adjust_lock); + cv_destroy(&arc_adjust_waiters_cv); + + /* + * 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(); + + 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. + */ + +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) { + ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); + return (B_FALSE); + } + if (HDR_HAS_L2HDR(hdr)) { + ARCSTAT_BUMP(arcstat_l2_write_in_l2); + return (B_FALSE); + } + if (HDR_IO_IN_PROGRESS(hdr)) { + ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); + return (B_FALSE); + } + if (!HDR_L2CACHE(hdr)) { + ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); + return (B_FALSE); + } + + return (B_TRUE); +} + +static uint64_t +l2arc_write_size(void) +{ + uint64_t size; + + /* + * 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; + + 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)); + + /* if we were unable to find any usable vdevs, return NULL */ + if (vdev_is_dead(next->l2ad_vdev)) + 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() +{ + 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_dev_t *dev; + 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; + 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)); + + if (zio->io_error != 0) { + /* + * Error - drop L2ARC entry. + */ + list_remove(buflist, hdr); + l2arc_trim(hdr); + arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); + + ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr)); + ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); + + bytes_dropped += arc_hdr_size(hdr); + (void) 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); + } + + 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); + + vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); + + l2arc_do_free_on_write(); + + kmem_free(cb, sizeof (l2arc_write_callback_t)); +} + +/* + * 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) +{ + l2arc_read_callback_t *cb; + arc_buf_hdr_t *hdr; + kmutex_t *hash_lock; + boolean_t valid_cksum; + + ASSERT3P(zio->io_vd, !=, NULL); + ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); + + spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); + + cb = zio->io_private; + 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) { + 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); + zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd; + } + + ASSERT3P(zio->io_abd, !=, NULL); + + /* + * Check this survived the L2ARC journey. + */ + ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd); + 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 */ + + valid_cksum = arc_cksum_is_equal(hdr, zio); + if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { + mutex_exit(hash_lock); + zio->io_private = hdr; + arc_read_done(zio); + } else { + mutex_exit(hash_lock); + /* + * 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) + 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); + + ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); + + zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, + hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done, + hdr, zio->io_priority, cb->l2rcb_flags, + &cb->l2rcb_zb)); + } + } + + 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 <= 3); + + 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; + } + + /* + * 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)); +} + +/* + * 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; + + buflist = &dev->l2ad_buflist; + + if (!all && dev->l2ad_first) { + /* + * This is the first sweep through the device. There is + * nothing to evict. + */ + return; + } + + if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { + /* + * When nearing the end of the device, evict to the end + * before the device write hand jumps to the start. + */ + 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); + +top: + mutex_enter(&dev->l2ad_mtx); + for (hdr = list_tail(buflist); 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. Retry. + */ + ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); + mutex_exit(&dev->l2ad_mtx); + mutex_enter(hash_lock); + mutex_exit(hash_lock); + goto top; + } + + /* + * 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 >= taddr || + 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); +} + +/* + * 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). + */ +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; + zio_t *pio, *wzio; + uint64_t guid = spa_load_guid(spa); + int try; + + 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); + + ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); + /* + * Copy buffers for L2ARC writing. + */ + for (try = 0; try <= 3; try++) { + multilist_sublist_t *mls = l2arc_sublist_lock(try); + uint64_t passed_sz = 0; + + ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); + + /* + * 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); + if (hdr == NULL) + ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); + + 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; + + if (arc_warm == B_FALSE) + hdr_prev = multilist_sublist_next(mls, hdr); + else + hdr_prev = multilist_sublist_prev(mls, hdr); + ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, + HDR_GET_LSIZE(hdr)); + + hash_lock = HDR_LOCK(hdr); + if (!mutex_tryenter(hash_lock)) { + ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); + /* + * Skip this buffer rather than waiting. + */ + continue; + } + + passed_sz += HDR_GET_LSIZE(hdr); + if (passed_sz > headroom) { + /* + * Searched too far. + */ + mutex_exit(hash_lock); + ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); + 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); + ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); + ASSERT3U(arc_hdr_size(hdr), >, 0); + uint64_t psize = arc_hdr_size(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); + ARCSTAT_BUMP(arcstat_l2_write_full); + break; + } + + 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; + pio = zio_root(spa, l2arc_write_done, cb, + ZIO_FLAG_CANFAIL); + ARCSTAT_BUMP(arcstat_l2_write_pios); + } + + hdr->b_l2hdr.b_dev = dev; + hdr->b_l2hdr.b_daddr = dev->l2ad_hand; + arc_hdr_set_flags(hdr, + ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); + + mutex_enter(&dev->l2ad_mtx); + list_insert_head(&dev->l2ad_buflist, hdr); + mutex_exit(&dev->l2ad_mtx); + + (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr); + + /* + * Normally the L2ARC can 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. + * Another case where we need to create a copy of the + * data is when the buffer size is not device-aligned + * and we need to pad the block to make it such. + * That also keeps the clock hand suitably aligned. + * + * To ensure that the 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. + */ + abd_t *to_write; + if (!HDR_SHARED_DATA(hdr) && psize == asize) { + to_write = hdr->b_l1hdr.b_pabd; + } else { + to_write = abd_alloc_for_io(asize, + HDR_ISTYPE_METADATA(hdr)); + abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize); + if (asize != psize) { + abd_zero_off(to_write, psize, + asize - psize); + } + l2arc_free_abd_on_write(to_write, asize, + arc_buf_type(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; + + mutex_exit(hash_lock); + + (void) 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); + return (0); + } + + ASSERT3U(write_psize, <=, 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); + vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0); + + /* + * Bump device hand to the device start if it is approaching the end. + * l2arc_evict() will already have evicted ahead for this case. + */ + if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { + dev->l2ad_hand = dev->l2ad_start; + dev->l2ad_first = B_FALSE; + } + + dev->l2ad_writing = B_TRUE; + (void) zio_wait(pio); + dev->l2ad_writing = B_FALSE; + + 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 __unused) +{ + callb_cpr_t cpr; + l2arc_dev_t *dev; + spa_t *spa; + uint64_t size, wrote; + clock_t begin, next = ddi_get_lbolt(); + + CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); + + mutex_enter(&l2arc_feed_thr_lock); + + while (l2arc_thread_exit == 0) { + CALLB_CPR_SAFE_BEGIN(&cpr); + (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, + next - ddi_get_lbolt()); + 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(); + + /* + * 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); + } + + 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) +{ + 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 != NULL); +} + +/* + * 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; + + ASSERT(!l2arc_vdev_present(vd)); + + vdev_ashift_optimize(vd); + + /* + * Create a new l2arc device entry. + */ + adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); + adddev->l2ad_spa = spa; + adddev->l2ad_vdev = vd; + adddev->l2ad_start = VDEV_LABEL_START_SIZE; + adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); + adddev->l2ad_hand = adddev->l2ad_start; + adddev->l2ad_first = B_TRUE; + adddev->l2ad_writing = B_FALSE; + + 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)); + + vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); + refcount_create(&adddev->l2ad_alloc); + + /* + * 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); +} + +/* + * Remove a vdev from the L2ARC. + */ +void +l2arc_remove_vdev(vdev_t *vd) +{ + l2arc_dev_t *dev, *nextdev, *remdev = NULL; + + /* + * Find the device by vdev + */ + mutex_enter(&l2arc_dev_mtx); + for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { + nextdev = list_next(l2arc_dev_list, dev); + if (vd == dev->l2ad_vdev) { + remdev = dev; + break; + } + } + ASSERT3P(remdev, !=, NULL); + + /* + * Remove device from global list + */ + 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); + mutex_destroy(&remdev->l2ad_mtx); + refcount_destroy(&remdev->l2ad_alloc); + kmem_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_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) +{ + /* + * This is called from dmu_fini(), which is called from spa_fini(); + * Because of this, we can assume that all l2arc devices have + * already been removed when the pools themselves were removed. + */ + + l2arc_do_free_on_write(); + + mutex_destroy(&l2arc_feed_thr_lock); + cv_destroy(&l2arc_feed_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 & FWRITE)) + return; + + (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, + TS_RUN, minclsyspri); +} + +void +l2arc_stop(void) +{ + if (!(spa_mode_global & FWRITE)) + 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); +} |