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* Add full SELinux supportMatthew Thode2013-12-191-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Four new dataset properties have been added to support SELinux. They are 'context', 'fscontext', 'defcontext' and 'rootcontext' which map directly to the context options described in mount(8). When one of these properties is set to something other than 'none'. That string will be passed verbatim as a mount option for the given context when the filesystem is mounted. For example, if you wanted the rootcontext for a filesystem to be set to 'system_u:object_r:fs_t' you would set the property as follows: $ zfs set rootcontext="system_u:object_r:fs_t" storage-pool/media This will ensure the filesystem is automatically mounted with that rootcontext. It is equivalent to manually specifying the rootcontext with the -o option like this: $ zfs mount -o rootcontext=system_u:object_r:fs_t storage-pool/media By default all four contexts are set to 'none'. Further information on SELinux contexts is detailed in mount(8) and selinux(8) man pages. Signed-off-by: Matthew Thode <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Signed-off-by: Richard Yao <[email protected]> Closes #1504
* cstyle: Resolve C style issuesMichael Kjorling2013-12-1822-239/+231
| | | | | | | | | | | | | | | | | | The vast majority of these changes are in Linux specific code. They are the result of not having an automated style checker to validate the code when it was originally written. Others were caused when the common code was slightly adjusted for Linux. This patch contains no functional changes. It only refreshes the code to conform to style guide. Everyone submitting patches for inclusion upstream should now run 'make checkstyle' and resolve any warning prior to opening a pull request. The automated builders have been updated to fail a build if when 'make checkstyle' detects an issue. Signed-off-by: Brian Behlendorf <[email protected]> Closes #1821
* Sync /dev/zfs ioctl orderingBrian Behlendorf2013-12-161-4/+18
| | | | | | | | | | | | | | | | | | | | | | In order to minimize any future disruption caused by the addition and removal /dev/zfs ioctls this patch makes the following changes. 1) Sync ZoL's ioctl ordering such that it matches Illumos. For historic reasons the ZFS_IOC_DESTROY_SNAPS and ZFS_IOC_POOL_REGUID ioctls were out of order. 2) Move Linux and FreeBSD specific ioctls in to their own reserved ranges. This allows us to preserve the existing ordering when new ioctls are added by either Illumos or FreeBSD. When an ioctl is no longer needed it should be retired in place. This change alters the ZFS user/kernel ABI so make sure you rebuild both your user and kernel modules. However, it should allow for a much stabler interface going forward. Signed-off-by: Brian Behlendorf <[email protected]> Signed-off-by: Ned Bass <[email protected]> Closes #1973
* Remove ZFC_IOC_*_MINOR ioctl()sBrian Behlendorf2013-12-164-8/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Early versions of ZFS coordinated the creation and destruction of device minors from userspace. This was inherently racy and in late 2009 these ioctl()s were removed leaving everything up to the kernel. This significantly simplified the code. However, we never picked up these changes in ZoL since we'd already significantly adjusted this code for Linux. This patch aims to rectify that by finally removing ZFC_IOC_*_MINOR ioctl()s and moving all the functionality down in to the kernel. Since this cleanup will change the kernel/user ABI it's being done in the same tag as the previous libzfs_core ABI changes. This will minimize, but not eliminate, the disruption to end users. Once merged ZoL, Illumos, and FreeBSD will basically be back in sync in regards to handling ZVOLs in the common code. While each platform must have its own custom zvol.c implemenation the interfaces provided are consistent. NOTES: 1) This patch introduces one subtle change in behavior which could not be easily avoided. Prior to this change callers of 'zfs create -V ...' were guaranteed that upon exit the /dev/zvol/ block device link would be created or an error returned. That's no longer the case. The utilities will no longer block waiting for the symlink to be created. Callers are now responsible for blocking, this is why a 'udev_wait' call was added to the 'label' function in scripts/common.sh. 2) The read-only behavior of a ZVOL now solely depends on if the ZVOL_RDONLY bit is set in zv->zv_flags. The redundant policy setting in the gendisk structure was removed. This both simplifies the code and allows us to safely leverage set_disk_ro() to issue a KOBJ_CHANGE uevent. See the comment in the code for futher details on this. 3) Because __zvol_create_minor() and zvol_alloc() may now be called in a sync task they must use KM_PUSHPAGE. References: illumos/illumos-gate@681d9761e8516a7dc5ab6589e2dfe717777e1123 Signed-off-by: Brian Behlendorf <[email protected]> Signed-off-by: Ned Bass <[email protected]> Signed-off-by: Tim Chase <[email protected]> Closes #1969
* Fix zstream_t incorrect typeShen Yan2013-12-101-1/+1
| | | | | | | | | | | | | The DMU zfetch code organizes streams with lists not avl trees. A avl_node_t was mistakenly used for a list_node_t in the zstream_t type. This is incorrect (but harmless) and when unnoticed because: 1) The list functions explicitly cast the value preventing a warning, 2) sizeof(avl_node_t) >= sizeof(list_node_t) so no overrun occurs, and 3) The calculated offset is the same regardless of the type. Signed-off-by: Brian Behlendorf <[email protected]> Closes #1946
* Illumos #4045 write throttle & i/o scheduler performance workMatthew Ahrens2013-12-0615-70/+163
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Christopher Siden <[email protected]> Reviewed by: Ned Bass <[email protected]> Reviewed by: Brendan Gregg <[email protected]> Approved by: Robert Mustacchi <[email protected]> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1913
* Only commit the ZIL once in zpl_writepages() (msync() case).Etienne Dechamps2013-11-232-1/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, using msync() results in the following code path: sys_msync -> zpl_fsync -> filemap_write_and_wait_range -> zpl_writepages -> write_cache_pages -> zpl_putpage In such a code path, zil_commit() is called as part of zpl_putpage(). This means that for each page, the write is handed to the DMU, the ZIL is committed, and only then do we move on to the next page. As one might imagine, this results in atrocious performance where there is a large number of pages to write: instead of committing a batch of N writes, we do N commits containing one page each. In some extreme cases this can result in msync() being ~700 times slower than it should be, as well as very inefficient use of ZIL resources. This patch fixes this issue by making sure that the requested writes are batched and then committed only once. Unfortunately, the implementation is somewhat non-trivial because there is no way to run write_cache_pages in SYNC mode (so that we get all pages) without making it wait on the writeback tag for each page. The solution implemented here is composed of two parts: - I added a new callback system to the ZIL, which allows the caller to be notified when its ITX gets written to stable storage. One nice thing is that the callback is called not only in zil_commit() but in zil_sync() as well, which means that the caller doesn't have to care whether the write ended up in the ZIL or the DMU: it will get notified as soon as it's safe, period. This is an improvement over dmu_tx_callback_register() that was used previously, which only supports DMU writes. The rationale for this change is to allow zpl_putpage() to be notified when a ZIL commit is completed without having to block on zil_commit() itself. - zpl_writepages() now calls write_cache_pages in non-SYNC mode, which will prevent (1) write_cache_pages from blocking, and (2) zpl_putpage from issuing ZIL commits. zpl_writepages() will issue the commit itself instead of relying on zpl_putpage() to do it, thus nicely batching the writes. Note, however, that we still have to call write_cache_pages() again in SYNC mode because there is an edge case documented in the implementation of write_cache_pages() whereas it will not give us all dirty pages when running in non-SYNC mode. Thus we need to run it at least once in SYNC mode to make sure we honor persistency guarantees. This only happens when the pages are modified at the same time msync() is running, which should be rare. In most cases there won't be any additional pages and this second call will do nothing. Note that this change also fixes a bug related to #907 whereas calling msync() on pages that were already handed over to the DMU in a previous writepages() call would make msync() block until the next TXG sync instead of returning as soon as the ZIL commit is complete. The new callback system fixes that problem. Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1849 Closes #907
* Illumos #2583Yuri Pankov2013-11-211-2/+3
| | | | | | | | | | | | 2583 Add -p (parsable) option to zfs list References: https://www.illumos.org/issues/2583 illumos/illumos-gate@43d68d68c1ce08fb35026bebfb141af422e7082e Ported-by: Gregor Kopka <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes: #937
* Add I/O Read/Write AccountingBrian Behlendorf2013-11-211-0/+1
| | | | | | | | | | | | | Because ZFS bypasses the page cache we don't inherit per-task I/O accounting for free. However, the Linux kernel does provide helper functions allow us to perform our own accounting. These are most commonly used for direct IO which also bypasses the page cache, but they can be used for the common read/write call paths as well. Signed-off-by: Pavel Snajdr <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #313 Closes #1275
* Honor CONFIG_FS_POSIX_ACL kernel optionMassimo Maggi2013-11-052-0/+16
| | | | | | | | | | | | | | | | The required Posix ACL interfaces are only available for kernels with CONFIG_FS_POSIX_ACL defined. Therefore, only enable Posix ACL support for these kernels. All major distribution kernels enable CONFIG_FS_POSIX_ACL by default. If your kernel does not support Posix ACLs the following warning will be printed at ZFS module load time. "ZFS: Posix ACLs disabled by kernel" Signed-off-by: Massimo Maggi <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1825
* Illumos #3954, #4080, #4081George Wilson2013-11-051-1/+4
| | | | | | | | | | | | | | | | | | | 3954 metaslabs continue to load even after hitting zfs_mg_alloc_failure limit 4080 zpool clear fails to clear pool 4081 need zfs_mg_noalloc_threshold Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Approved by: Richard Lowe <[email protected]> References: https://www.illumos.org/issues/3954 https://www.illumos.org/issues/4080 https://www.illumos.org/issues/4081 illumos/illumos-gate@22e30981d82a0b6dc89253596ededafae8655e00 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #4047Matthew Ahrens2013-11-052-3/+5
| | | | | | | | | | | | | | | | | | | | | 4047 panic from dbuf_free_range() from dmu_free_object() while doing zfs receive Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Approved by: Dan McDonald <[email protected]> References: https://www.illumos.org/issues/4047 illumos/illumos-gate@713d6c208802cfbb806329ec0d154b641b80c355 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775 Porting notes: 1. The exported symbol dmu_free_object() was renamed to dmu_free_long_object() in Illumos.
* Illumos #3996Matthew Ahrens2013-11-052-2/+3
| | | | | | | | | | | | | | | | | 3996 want a libzfs_core API to rollback to latest snapshot Reviewed by: Christopher Siden <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Andy Stormont <[email protected]> Approved by: Richard Lowe <[email protected]> References: https://www.illumos.org/issues/3996 illumos/illumos-gate@a7027df17fad220a20367b9d1eb251bc6300d203 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #3956, #3957, #3958, #3959, #3960, #3961, #3962George Wilson2013-11-054-5/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 3956 ::vdev -r should work with pipelines 3957 ztest should update the cachefile before killing itself 3958 multiple scans can lead to partial resilvering 3959 ddt entries are not always resilvered 3960 dsl_scan can skip over dedup-ed blocks if physical birth != logical birth 3961 freed gang blocks are not resilvered and can cause pool to suspend 3962 ztest should print out zfs debug buffer before exiting Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Approved by: Richard Lowe <[email protected]> References: https://www.illumos.org/issues/3956 https://www.illumos.org/issues/3957 https://www.illumos.org/issues/3958 https://www.illumos.org/issues/3959 https://www.illumos.org/issues/3960 https://www.illumos.org/issues/3961 https://www.illumos.org/issues/3962 illumos/illumos-gate@b4952e17e8858d3225793b28788278de9fe6038d Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Porting notes: 1. zfs_dbgmsg_print() is only used in userland. Since we do not have mdb on Linux, it does not make sense to make it available in the kernel. This means that a build failure will occur if any future kernel patch depends on it. However, that is unlikely given that this functionality was added to support zdb. 2. zfs_dbgmsg_print() is only invoked for -VVV or greater log levels. This preserves the existing behavior of minimal noise when running with -V, and -VV. 3. In vdev_config_generate() the call to nvlist_alloc() was not changed to fnvlist_alloc() because we must pass KM_PUSHPAGE in the txg_sync context.
* Illumos #3834Matthew Ahrens2013-11-052-1/+8
| | | | | | | | | | | | | | | 3834 incremental replication of 'holey' file systems is slow Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Approved by: Richard Lowe <[email protected]> References: https://www.illumos.org/issues/3834 illumos/illumos-gate@ca48f36f20f6098ceb19d5b084b6b3d4b8eca9fa Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #3836Matthew Ahrens2013-11-051-3/+2
| | | | | | | | | | | | | | | 3836 zio_free() can be processed immediately in the common case Reviewed by: George Wilson <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Approved by: Dan McDonald <[email protected]> References: https://www.illumos.org/issues/3836 illumos/illumos-gate@9cb154a3c9f170904dce9bad5bd5a7d256b922a4 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #3112, #3113, #3114Matthew Ahrens2013-11-052-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 3112 ztest does not honor ZFS_DEBUG 3113 ztest should use watchpoints to protect frozen arc bufs 3114 some leaked nvlists in zfsdev_ioctl Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Matt Amdur <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Approved by: Eric Schrock <[email protected]> References: https://www.illumos.org/issues/3112 https://www.illumos.org/issues/3113 https://www.illumos.org/issues/3114 illumos/illumos-gate@cd1c8b85eb30b568e9816221430c479ace7a559d The /proc/self/cmd watchpoint interface is specific to Solaris. Therefore, the #3113 implementation was reworked to use the more portable mprotect(2) system call. When the pages are watched they are marked read-only for protection. Any write to the protected address range immediately trigger a SIGSEGV. The pages are marked writable again when they are unwatched. Ported-by: Brian Behlendorf <[email protected]> Issue #1489
* Illumos #3236George Wilson2013-11-054-19/+96
| | | | | | | | | | | | | | | | | | | | 3236 zio nop-write Reviewed by: Matt Ahrens <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Christopher Siden <[email protected]> Approved by: Garrett D'Amore <[email protected]> References: illumos/illumos-gate@80901aea8e78a2c20751f61f01bebd1d5b5c2ba5 https://www.illumos.org/issues/3236 Porting Notes 1. This patch is being merged dispite an increased instance of https://www.illumos.org/issues/3113 being triggered by ztest. Ported-by: Brian Behlendorf <[email protected]> Issue #1489
* Illumos #3875Keith M Wesolowski2013-11-043-3/+5
| | | | | | | | | | | | | | | 3875 panic in zfs_root() after failed rollback Reviewed by: Jerry Jelinek <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Approved by: Gordon Ross <[email protected]> References: https://www.illumos.org/issues/3875 illumos/illumos-gate@91948b51b8e978ddc88a36b2bc3ae83c20cdc9aa Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #3888Matthew Ahrens2013-11-042-12/+14
| | | | | | | | | | | | | | | | | | | | | | | | 3888 zfs recv -F should destroy any snapshots created since the incremental source Reviewed by: George Wilson <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Peng Dai <[email protected]> Approved by: Richard Lowe <[email protected]> References: https://www.illumos.org/issues/3888 illumos/illumos-gate@34f2f8cf94052481c81be2e134b94a00b501bf21 Porting notes: 1. Commit 1fde1e37208c2f56c72c70a06676676f04b65998 wrapped a declaration in dsl_dataset_modified_since_lastsnap in ASSERTV(). The ASSERTV() and local variable have been removed to avoid an unused variable warning. Signed-off-by: Brian Behlendorf <[email protected]> Ported-by: Richard Yao <[email protected]> Issue #1775
* Illumos #3894Keith M Wesolowski2013-11-042-1/+2
| | | | | | | | | | | | | | 3894 zfs should not allow snapshot of inconsistent dataset Reviewed by: Matthew Ahrens <[email protected]> Approved by: Gordon Ross <[email protected]> References: https://www.illumos.org/issues/3894 illumos/illumos-gate@ca48f36f20f6098ceb19d5b084b6b3d4b8eca9fa Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #3740Steven Hartland2013-11-043-5/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 3740 Poor ZFS send / receive performance due to snapshot hold / release processing Reviewed by: Matthew Ahrens <[email protected]> Approved by: Christopher Siden <[email protected]> References: https://www.illumos.org/issues/3740 illumos/illumos-gate@a7a845e4bf22fd1b2a284729ccd95c7370a0438c Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775 Porting notes: 1. 13fe019870c8779bf2f5b3ff731b512cf89133ef introduced a merge conflict in dsl_dataset_user_release_tmp where some variables were moved outside of the preprocessor directive. 2. dea9dfefdd747534b3846845629d2200f0616dad made the previous merge conflict worse by switching KM_SLEEP to KM_PUSHPAGE. This is notable because this commit refactors the code, adding a new KM_SLEEP allocation. It is not clear to me whether this should be converted to KM_PUSHPAGE. 3. We had a merge conflict in libzfs_sendrecv.c because of copyright notices. 4. Several small C99 compatibility fixed were made.
* Illumos #3744Will Andrews2013-11-041-1/+1
| | | | | | | | | | | | | | | | | | | | | | 3744 zfs shouldn't ignore errors unmounting snapshots Reviewed by: Matthew Ahrens <[email protected]> Approved by: Christopher Siden <[email protected]> References: https://www.illumos.org/issues/3744 illumos/illumos-gate@fc7a6e3fefc649cb65c8e2a35d194781445008b0 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775 Porting notes: 1. There is no clear way to distinguish between a failure when we tried to unmount the snapdir of a zvol (which does not exist) and the failure when we try to unmount a snapdir of a dataset, so the changes to zfs_unmount_snap() were dropped in favor of an altered Linux function that unconditionally returns 0.
* Illumos #3742Will Andrews2013-11-0415-92/+87
| | | | | | | | | | | | | | | | | | | | | 3742 zfs comments need cleaner, more consistent style Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Eric Schrock <[email protected]> Approved by: Christopher Siden <[email protected]> References: https://www.illumos.org/issues/3742 illumos/illumos-gate@f7170741490edba9d1d9c697c177c887172bc741 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775 Porting notes: 1. The change to zfs_vfsops.c was dropped because it involves zfs_mount_label_policy, which does not exist in the Linux port.
* Illumos #3741Will Andrews2013-11-041-0/+8
| | | | | | | | | | | | | | | 3741 zfs needs better comments Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Eric Schrock <[email protected]> Approved by: Christopher Siden <[email protected]> References: https://www.illumos.org/issues/3741 illumos/illumos-gate@3e30c24aeefdee1631958ecf17f18da671781956 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #3582, #3584Adam Leventhal2013-11-043-10/+7
| | | | | | | | | | | | | | | | | | | | 3582 zfs_delay() should support a variable resolution 3584 DTrace sdt probes for ZFS txg states Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Reviewed by: Dan McDonald <[email protected]> Reviewed by: Richard Elling <[email protected]> Approved by: Garrett D'Amore <[email protected]> References: https://www.illumos.org/issues/3582 illumos/illumos-gate@0689f76 Ported by: Ned Bass <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Illumos #3642, #3643George Wilson2013-11-012-3/+49
| | | | | | | | | | | | | | | | | | | | | | | | | | 3642 dsl_scan_active() should not issue I/O to determine if async destroying is active 3643 txg_delay should not hold the tc_lock Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Approved by: Gordon Ross <[email protected]> References: https://www.illumos.org/issues/3642 https://www.illumos.org/issues/3643 illumos/illumos-gate@4a92375985c37d61406d66cd2b10ee642eb1f5e7 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775 Porting Notes: 1. The alignment assumptions for the tx_cpu structure assume that a kmutex_t is 8 bytes. This isn't true under Linux but tc_pad[] was adjusted anyway for consistency since this structure was never carefully aligned in ZoL. If careful alignment does impact performance significantly this should be reworked to be portable.
* Illumos #3598Matthew Ahrens2013-10-311-14/+33
| | | | | | | | | | | | | | | | | | | | | | | | | | | 3598 want to dtrace when errors are generated in zfs Reviewed by: Dan Kimmel <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Christopher Siden <[email protected]> Approved by: Garrett D'Amore <[email protected]> References: https://www.illumos.org/issues/3598 illumos/illumos-gate@be6fd75a69ae679453d9cda5bff3326111e6d1ca Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775 Porting notes: 1. include/sys/zfs_context.h has been modified to render some new macros inert until dtrace is available on Linux. 2. Linux-specific changes have been adapted to use SET_ERROR(). 3. I'm NOT happy about this change. It does nothing but ugly up the code under Linux. Unfortunately we need to take it to avoid more merge conflicts in the future. -Brian
* Illumos #3588Matthew Ahrens2013-10-311-0/+2
| | | | | | | | | | | | | | | | | 3588 provide zfs properties for logical (uncompressed) space used and referenced Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Dan McDonald <[email protected]> Reviewed by: Richard Elling <[email protected]> Approved by: Richard Lowe <[email protected]> References: https://www.illumos.org/issues/3588 illumos/illumos-gate@77372cb0f35e8d3615ca2e16044f033397e88e21 Ported-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]>
* Illumos #3537Matthew Ahrens2013-10-312-2/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 3537 want pool io kstats Reviewed by: George Wilson <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: Eric Schrock <[email protected]> Reviewed by: Sa?o Kiselkov <[email protected]> Reviewed by: Garrett D'Amore <[email protected]> Reviewed by: Brendan Gregg <[email protected]> Approved by: Gordon Ross <[email protected]> References: http://www.illumos.org/issues/3537 illumos/illumos-gate@c3a6601 Ported by: Cyril Plisko <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Porting Notes: 1. The patch was restructured to take advantage of the existing spa statistics infrastructure. To accomplish this the kstat was moved in to spa->io_stats and the init/destroy code moved to spa_stats.c. 2. The I/O kstat was simply named <pool> which conflicted with the pool directory we had already created. Therefore it was renamed to <pool>/io 3. An update handler was added to allow the kstat to be zeroed.
* Add missing code to zfs_debug.{c,h}Richard Yao2013-10-291-4/+29
| | | | | | This is required to make Illumos 3962 merge. Signed-off-by: Richard Yao <[email protected]>
* Add missing copyright notices from IllumosRichard Yao2013-10-291-0/+1
| | | | | | | | This resolves merge conflicts when merging Illumos #3588 and Illumos #4047. Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1775
* Posix ACL SupportMassimo Maggi2013-10-296-0/+200
| | | | | | | | | | | | | | | | | | | | | | | | This change adds support for Posix ACLs by storing them as an xattr which is common practice for many Linux file systems. Since the Posix ACL is stored as an xattr it will not overwrite any existing ZFS/NFSv4 ACLs which may have been set. The Posix ACL will also be non-functional on other platforms although it may be visible as an xattr if that platform understands SA based xattrs. By default Posix ACLs are disabled but they may be enabled with the new 'aclmode=noacl|posixacl' property. Set the property to 'posixacl' to enable them. If ZFS/NFSv4 ACL support is ever added an appropriate acltype will be added. This change passes the POSIX Test Suite cleanly with the exception of xacl/00.t test 45 which is incorrect for Linux (Ext4 fails too). http://www.tuxera.com/community/posix-test-suite/ Signed-off-by: Massimo Maggi <[email protected]> Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #170
* Introduce zpool_get_prop_literal interfaceRalf Ertzinger2013-10-281-0/+2
| | | | | | | | | | | | | | | | | | | | | This change introduces zpool_get_prop_literal. It's an expanded version of zpool_get_prop taking one additional boolean parameter. With this parameter set to B_FALSE it will behave identically to zpool_get_prop. Setting it to B_TRUE will return full precision numbers for the following properties: ZPOOL_PROP_SIZE ZPOOL_PROP_ALLOCATED ZPOOL_PROP_FREE ZPOOL_PROP_FREEING ZPOOL_PROP_EXPANDSZ ZPOOL_PROP_ASHIFT Also introduced is a wrapper function for zpool_get_prop making it use zpool_get_prop_literal in the background. Signed-off-by: Brian Behlendorf <[email protected]> Issue #1813
* Add visibility in to cached dbufsBrian Behlendorf2013-10-253-0/+35
| | | | | | | | | | | | | | | | | | | | | | | | Currently there is no mechanism to inspect which dbufs are being cached by the system. There are some coarse counters in arcstats by they only give a rough idea of what's being cached. This patch aims to improve the current situation by adding a new dbufs kstat. When read this new kstat will walk all cached dbufs linked in to the dbuf_hash. For each dbuf it will dump detailed information about the buffer. It will also dump additional information about the referenced arc buffer and its related dnode. This provides a more complete view in to exactly what is being cached. With this generic infrastructure in place utilities can be written to post-process the data to understand exactly how the caching is working. For example, the data could be processed to show a list of all cached dnodes and how much space they're consuming. Or a similar list could be generated based on dnode type. Many other ways to interpret the data exist based on what kinds of questions you're trying to answer. Signed-off-by: Brian Behlendorf <[email protected]> Signed-off-by: Prakash Surya <[email protected]>
* Add visibility in to dmu_tx_assign timesBrian Behlendorf2013-10-251-0/+2
| | | | | | | | | | | This change adds a new kstat to gain some visibility into the amount of time spent in each call to dmu_tx_assign. A histogram is exported via the new dmu_tx_assign file. The information contained in this histogram is the frequency dmu_tx_assign took to complete given an interval range. Signed-off-by: Prakash Surya <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]>
* Add visibility in to txg sync behaviorBrian Behlendorf2013-10-251-0/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This change is an attempt to add visibility in to how txgs are being formed on a system, in real time. To do this, a list was added to the in memory SPA data structure for a pool, with each element on the list corresponding to txg. These entries are then exported through the kstat interface, which can then be interpreted in userspace. For each txg, the following information is exported: * Unique txg number (uint64_t) * The time the txd was born (hrtime_t) (*not* wall clock time; relative to the other entries on the list) * The current txg state ((O)pen/(Q)uiescing/(S)yncing/(C)ommitted) * The number of reserved bytes for the txg (uint64_t) * The number of bytes read during the txg (uint64_t) * The number of bytes written during the txg (uint64_t) * The number of read operations during the txg (uint64_t) * The number of write operations during the txg (uint64_t) * The time the txg was closed (hrtime_t) * The time the txg was quiesced (hrtime_t) * The time the txg was synced (hrtime_t) Note that while the raw kstat now stores relative hrtimes for the open, quiesce, and sync times. Those relative times are used to calculate how long each state took and these deltas and printed by output handlers. Signed-off-by: Brian Behlendorf <[email protected]>
* Add visibility in to arc_readPrakash Surya2013-10-254-2/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This change is an attempt to add visibility into the arc_read calls occurring on a system, in real time. To do this, a list was added to the in memory SPA data structure for a pool, with each element on the list corresponding to a call to arc_read. These entries are then exported through the kstat interface, which can then be interpreted in userspace. For each arc_read call, the following information is exported: * A unique identifier (uint64_t) * The time the entry was added to the list (hrtime_t) (*not* wall clock time; relative to the other entries on the list) * The objset ID (uint64_t) * The object number (uint64_t) * The indirection level (uint64_t) * The block ID (uint64_t) * The name of the function originating the arc_read call (char[24]) * The arc_flags from the arc_read call (uint32_t) * The PID of the reading thread (pid_t) * The command or name of thread originating read (char[16]) From this exported information one can see, in real time, exactly what is being read, what function is generating the read, and whether or not the read was found to be already cached. There is still some work to be done, but this should serve as a good starting point. Specifically, dbuf_read's are not accounted for in the currently exported information. Thus, a follow up patch should probably be added to export these calls that never call into arc_read (they only hit the dbuf hash table). In addition, it might be nice to create a utility similar to "arcstat.py" to digest the exported information and display it in a more readable format. Or perhaps, log the information and allow for it to be "replayed" at a later time. Signed-off-by: Prakash Surya <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]>
* Revert "Add txgs-<pool> kstat file"Brian Behlendorf2013-10-251-15/+0
| | | | This reverts commit e95853a331529a6cb96fdf10476c53441e59f4e1.
* Revert "Add new kstat for monitoring time in dmu_tx_assign"Brian Behlendorf2013-10-251-5/+0
| | | | | | This reverts commit 92334b14ec378b1693573b52c09816bbade9cf3e. Signed-off-by: Brian Behlendorf <[email protected]>
* Increase default udev wait timeBrian Behlendorf2013-10-221-0/+5
| | | | | | | | | | | | | | | | | | When creating a new pool, or adding/replacing a disk in an existing pool, partition tables will be automatically created on the devices. Under normal circumstances it will take less than a second for udev to create the expected device files under /dev/. However, it has been observed that if the system is doing heavy IO concurrently udev may take far longer. If you also throw in some cheap dodgy hardware it may take even longer. To prevent zpool commands from failing due to this the default wait time for udev is being increased to 30 seconds. This will have no impact on normal usage, the increase timeout should only be noticed if your udev rules are incorrectly configured. Signed-off-by: Brian Behlendorf <[email protected]> Closes #1646
* Linux 3.11 compat: Rename LZ4 symbolsRichard Yao2013-10-221-2/+2
| | | | | | | | | | Linus Torvalds merged LZ4 into Linux 3.11. This causes a conflict whenever CONFIG_LZ4_DECOMPRESS=y or CONFIG_LZ4_COMPRESS=y are set in the kernel's .config. We rename the symbols to avoid the conflict. Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1789
* Illumos #3464Matthew Ahrens2013-09-0430-228/+386
| | | | | | | | | | | | | | | | | 3464 zfs synctask code needs restructuring Reviewed by: Dan Kimmel <[email protected]> Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Approved by: Garrett D'Amore <[email protected]> References: https://www.illumos.org/issues/3464 illumos/illumos-gate@3b2aab18808792cbd248a12f1edf139b89833c13 Ported-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1495
* Illumos #2882, #2883, #2900Matthew Ahrens2013-09-0415-135/+163
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 2882 implement libzfs_core 2883 changing "canmount" property to "on" should not always remount dataset 2900 "zfs snapshot" should be able to create multiple, arbitrary snapshots at once Reviewed by: George Wilson <[email protected]> Reviewed by: Chris Siden <[email protected]> Reviewed by: Garrett D'Amore <[email protected]> Reviewed by: Bill Pijewski <[email protected]> Reviewed by: Dan Kruchinin <[email protected]> Approved by: Eric Schrock <[email protected]> References: https://www.illumos.org/issues/2882 https://www.illumos.org/issues/2883 https://www.illumos.org/issues/2900 illumos/illumos-gate@4445fffbbb1ea25fd0e9ea68b9380dd7a6709025 Ported-by: Tim Chase <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1293 Porting notes: WARNING: This patch changes the user/kernel ABI. That means that the zfs/zpool utilities built from master are NOT compatible with the 0.6.2 kernel modules. Ensure you load the matching kernel modules from master after updating the utilities. Otherwise the zfs/zpool commands will be unable to interact with your pool and you will see errors similar to the following: $ zpool list failed to read pool configuration: bad address no pools available $ zfs list no datasets available Add zvol minor device creation to the new zfs_snapshot_nvl function. Remove the logging of the "release" operation in dsl_dataset_user_release_sync(). The logging caused a null dereference because ds->ds_dir is zeroed in dsl_dataset_destroy_sync() and the logging functions try to get the ds name via the dsl_dataset_name() function. I've got no idea why this particular code would have worked in Illumos. This code has subsequently been completely reworked in Illumos commit 3b2aab1 (3464 zfs synctask code needs restructuring). Squash some "may be used uninitialized" warning/erorrs. Fix some printf format warnings for %lld and %llu. Apply a few spa_writeable() changes that were made to Illumos in illumos/illumos-gate.git@cd1c8b8 as part of the 3112, 3113, 3114 and 3115 fixes. Add a missing call to fnvlist_free(nvl) in log_internal() that was added in Illumos to fix issue 3085 but couldn't be ported to ZoL at the time (zfsonlinux/zfs@9e11c73) because it depended on future work.
* Linux 3.11 compat: fops->iterate()Richard Yao2013-08-152-2/+61
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit torvalds/linux@2233f31aade393641f0eaed43a71110e629bb900 replaced ->readdir() with ->iterate() in struct file_operations. All filesystems must now use the new ->iterate method. To handle this the code was reworked to use the new ->iterate interface. Care was taken to keep the majority of changes confined to the ZPL layer which is already Linux specific. However, minor changes were required to the common zfs_readdir() function. Compatibility with older kernels was accomplished by adding versions of the trivial dir_emit* helper functions. Also the various *_readdir() functions were reworked in to wrappers which create a dir_context structure to pass to the new *_iterate() functions. Unfortunately, the new dir_emit* functions prevent us from passing a private pointer to the filldir function. The xattr directory code leveraged this ability through zfs_readdir() to generate the list of xattr names. Since we can no longer use zfs_readdir() a simplified zpl_xattr_readdir() function was added to perform the same task. Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1653 Issue #1591
* Illumos #3618 ::zio dcmd does not show timestamp dataMatthew Ahrens2013-08-122-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 3618 ::zio dcmd does not show timestamp data Reviewed by: Adam Leventhal <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Christopher Siden <[email protected]> Reviewed by: Garrett D'Amore <[email protected]> Approved by: Dan McDonald <[email protected]> References: http://www.illumos.org/issues/3618 illumos/illumos-gate@c55e05cb35da47582b7afd38734d2f0d9c6deb40 Notes on porting to ZFS on Linux: The original changeset mostly deals with mdb ::zio dcmd. However, in order to provide the requested functionality it modifies vdev and zio structures to keep the timing data in nanoseconds instead of ticks. It is these changes that are ported over in the commit in hand. One visible change of this commit is that the default value of 'zfs_vdev_time_shift' tunable is changed: zfs_vdev_time_shift = 6 to zfs_vdev_time_shift = 29 The original value of 6 was inherited from OpenSolaris and was subotimal - since it shifted the raw tick value - it didn't compensate for different tick frequencies on Linux and OpenSolaris. The former has HZ=1000, while the latter HZ=100. (Which itself led to other interesting performance anomalies under non-trivial load. The deadline scheduler delays the IO according to its priority - the lower priority the further the deadline is set. The delay is measured in units of "shifted ticks". Since the HZ value was 10 times higher, the delay units were 10 times shorter. Thus really low priority IO like resilver (delay is 10 units) and scrub (delay is 20 units) were scheduled much sooner than intended. The overall effect is that resilver and scrub IO consumed more bandwidth at the expense of the other IO.) Now that the bookkeeping is done is nanoseconds the shift behaves correctly for any tick frequency (HZ). Ported-by: Cyril Plisko <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1643
* Illumos #3964 L2ARC should always compress metadata buffersSaso Kiselkov2013-08-083-2/+5
| | | | | | | | | | | | 3964 L2ARC should always compress metadata buffers Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> References: https://www.illumos.org/issues/3964 Ported-by: Brian Behlendorf <[email protected]> Closes #1379
* Illumos #3137 L2ARC compressionSaso Kiselkov2013-08-083-3/+12
| | | | | | | | | | | | | | | | | | | | | | | 3137 L2ARC compression Reviewed by: George Wilson <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Approved by: Dan McDonald <[email protected]> References: illumos/illumos-gate@aad02571bc59671aa3103bb070ae365f531b0b62 https://www.illumos.org/issues/3137 http://wiki.illumos.org/display/illumos/L2ARC+Compression Notes for Linux port: A l2arc_nocompress module option was added to prevent the compression of l2arc buffers regardless of how a dataset's compression property is set. This allows the legacy behavior to be preserved. Ported by: James H <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1379
* Remove arc_data_buf_alloc()/arc_data_buf_free()Richard Yao2013-08-011-2/+0
| | | | | | | | | | These functions are used in neither Illumos nor ZFSOnLinux. They appear to have been replaced by arc_buf_alloc()/arc_buf_free(), so lets remove them. Signed-off-by: Richard Yao <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Issue #1614
* Add new kstat for monitoring time in dmu_tx_assignPrakash Surya2013-07-111-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This change adds a new kstat to gain some visibility into the amount of time spent in each call to dmu_tx_assign. A histogram is exported via a new dmu_tx_assign_histogram-$POOLNAME file. The information contained in this histogram is the frequency dmu_tx_assign took to complete given an interval range. For example, given the below histogram file: $ cat /proc/spl/kstat/zfs/dmu_tx_assign_histogram-tank 12 1 0x01 32 1536 19792068076691 20516481514522 name type data 1 us 4 859 2 us 4 252 4 us 4 171 8 us 4 2 16 us 4 0 32 us 4 2 64 us 4 0 128 us 4 0 256 us 4 0 512 us 4 0 1024 us 4 0 2048 us 4 0 4096 us 4 0 8192 us 4 0 16384 us 4 0 32768 us 4 1 65536 us 4 1 131072 us 4 1 262144 us 4 4 524288 us 4 0 1048576 us 4 0 2097152 us 4 0 4194304 us 4 0 8388608 us 4 0 16777216 us 4 0 33554432 us 4 0 67108864 us 4 0 134217728 us 4 0 268435456 us 4 0 536870912 us 4 0 1073741824 us 4 0 2147483648 us 4 0 one can see most calls to dmu_tx_assign completed in 32us or less, but a few outliers did not. Specifically, 4 of the calls took between 262144us and 131072us. This information is difficult, if not impossible, to gather without this change. Signed-off-by: Prakash Surya <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #1584