The .sync_fs fix as applied did not use the updated SPL credential API. This broke builds on Debian Lenny, this change applies the needed fix to use the portable API. The original credential changes are part of commit 81e97e21872a9c38ad66c37fafe1436ee25abee3.
Disable the normal reclaim path for the txg_sync thread. This ensures the thread will never enter dmu_tx_assign() which can otherwise occur due to direct reclaim. If this is allowed to happen the system can deadlock. Direct reclaim call path: ->shrink_icache_memory->prune_icache->dispose_list-> clear_inode->zpl_clear_inode->zfs_inactive->dmu_tx_assign
Under OpenSolaris all memory reclaim is done asyncronously. Under Linux memory reclaim is done asynchronously _and_ synchronously. When a process allocates memory with GFP_KERNEL it explicitly allows the kernel to do reclaim on its behalf to satify the allocation. If that GFP_KERNEL allocation fails the kernel may take more drastic measures to reclaim the memory such as killing user space processes. This was observed to happen with ZFS because the ARC could consume a large fraction of the system memory but no synchronous reclaim could be performed on it. The result was GFP_KERNEL allocations could fail resulting in OOM events, and only moments latter the arc_reclaim thread would free unused memory from the ARC. This change leaves the arc_thread in place to manage the fundamental ARC behavior. But it adds a synchronous (direct) reclaim path for the ARC which can be called when memory is badly needed. It also adds an asynchronous (indirect) reclaim path which is called much more frequently to prune the ARC slab caches.
The following useful values were missing the arcstats. This change adds them in to provide greater visibility in to the arcs behavior. arc_no_grow 4 0 arc_tempreserve 4 0 arc_loaned_bytes 4 0 arc_meta_used 4 624774592 arc_meta_limit 4 400785408 arc_meta_max 4 625594176
Under Linux a dentry referencing an inode must be instantiated before the inode is unlocked. To accomplish this without overly modifing the core ZFS code the dentry it passed via the vattr_t. There are cases such as replay when a dentry is not available. In which case it is obviously not initialized at inode creation time, if a dentry is needed it will be spliced as when required via d_lookup().
Making distclean in module
make[1]: Entering directory `/zfs/module'
make -C SUBDIRS=`pwd` clean
make: Entering an unknown directory
make: *** SUBDIRS=/zfs/module: No such file or directory. Stop.
When using --with-config=user the 'distclean' target would fail
because it assumes the kernel configuration infrastrure is set up.
This is not the case, nor does it need to be, because the
'--with-config=user' option will prune the entire ./module subtree
from SUBDIRS. This prevents most build rules from operating in the
./module directory.
However, the 'dist*' rules will still traverse this directory
because it is listed in DIST_SUBDIRS. This is correct because we
need to ensure the dist rules package the directory contents
regardless of the configuration for the 'dist' rule. The correct
way to handle this is to only invoke the kernel build system as
part of the 'clean' rule when CONFIG_KERNEL_TRUE is set.
Initial fix provided by Darik Horn <dajhorn@vanadac.com>.
This commit is a slightly refined form of the original.
Kernel threads which sleep uninterruptibly on Linux are marked in the (D) state. These threads are usually in the process of performing IO and are thus counted against the load average. The txg_quiesce and txg_sync threads were always sleeping uninterruptibly and thus inflating the load average. This change makes them sleep interruptibly. Some care is required however because these threads may now be woken early by signals. In this case the callers are all careful to check that the required conditions are met after waking up. If we're woken early due to a signal they will simply go back to sleep. In this case these changes are safe. Closes #175
The .freeze_fs/.unfreeze_fs hooks were not added until Linux 2.6.29 Since these hooks are currently unused they are being removed to allow support of older kernels.
As of Linux 2.6.29 a clean credential API was added to the Linux kernel. Previously the credential was embedded in the task_struct. Because the SPL already has considerable support for handling this API change the ZPL code has been updated to use the Solaris credential API.
Now that KM_SLEEP is not defined as GFP_NOFS there is the possibility of synchronous reclaim deadlocks. These deadlocks never existed in the original OpenSolaris code because all memory reclaim on Solaris is done asyncronously. Linux does both synchronous (direct) and asynchronous (indirect) reclaim. This commit addresses a deadlock caused by inode eviction. A KM_SLEEP allocation may trigger direct memory reclaim and shrink the inode cache. This can occur while a mutex in the array of ZFS_OBJ_HOLD mutexes is held. Through the ->shrink_icache_memory()->evict()->zfs_inactive()-> zfs_zinactive() call path the same mutex may be reacquired resulting in a deadlock. To avoid this deadlock the process must not reacquire the mutex when it is already holding it. This is a reasonable fix for now but longer term the ZFS_OBJ_HOLD mutex locking should be reevaluated. This infrastructure already prevents us from ever using the Linux lock dependency analysis tools, and it may limit scalability.