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* Replace sprintf()->snprintf() and strcpy()->strlcpy()Jorgen Lundman2020-06-071-2/+4
| | | | | | | | | | | | | | | The strcpy() and sprintf() functions are deprecated on some platforms. Care is needed to ensure correct size is used. If some platforms miss snprintf, we can add a #define to sprintf, likewise strlcpy(). The biggest change is adding a size parameter to zfs_id_to_fuidstr(). The various *_impl_get() functions are only used on linux and have not yet been updated. Reviewed by: Sean Eric Fagan <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Jorgen Lundman <[email protected]> Closes #10400
* Compile cityhash code into libzfsMatthew Ahrens2020-03-271-1/+1
| | | | | | | | | Make the cityhash code compile into libzfs, in preparation for the new "zstream" command. Reviewed-by: Paul Dagnelie <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> Closes #10152
* zio: dprintf_bp() if errors > 0 in zfs_blkptr_verify()Brian Behlendorf2020-03-041-0/+3
| | | | | | | | | Also dprintf_bp() in case BLK_VERIFY_HALT of zfs_blkptr_verify_log() since dprintf_bp() in zfs_blkptr_verify() will never be executed. Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Paul Zuchowski <[email protected]> Signed-off-by: Justin Keogh <[email protected]> Closes #10086
* Improve performance of zio_taskq_memberMatthew Ahrens2020-03-031-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | __zio_execute() calls zio_taskq_member() to determine if we are running in a zio interrupt taskq, in which case we may need to switch to processing this zio in a zio issue taskq. The call to zio_taskq_member() can become a performance bottleneck when we are processing a high rate of zio's. zio_taskq_member() calls taskq_member() on each of the zio interrupt taskqs, of which there are 21. This is slow because each call to taskq_member() does tsd_get(taskq_tsd), which on Linux is relatively slow. This commit improves the performance of zio_taskq_member() by having it cache the value of tsd_get(taskq_tsd), reducing the number of those calls to 1/21th of the current behavior. In a test case running `zfs send -c >/dev/null` of a filesystem with small blocks (average 2.5KB/block), zio_taskq_member() was using 6.7% of one CPU, and with this change it is reduced to 1.3%. Overall time to perform the `zfs send` reduced by 10% (~150,000 block/sec to ~165,000 blocks/sec). Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Serapheim Dimitropoulos <[email protected]> Reviewed-by: Ryan Moeller <[email protected]> Reviewed-by: Tony Nguyen <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> Closes #10070
* Improve zfs destroy performance with zio_t-free zio_free()Matthew Ahrens2020-02-281-21/+46
| | | | | | | | | | | | | | | | | | | | | | | | | | When "zfs destroy" is run, it completes quickly, and in the background we locate the blocks to free and free them. This background activity can be observed with `zpool get freeing` and `zpool wait -t free ...`. This background activity is processed by a single thread (the spa_sync thread) which calls zio_free() on each of the blocks to free. With even modest storage performance, the CPU consumption of zio_free() can be the performance bottleneck. Performance of zio_free() can be improved by not actually creating a zio_t in the common case (non-dedup, non-gang), instead calling metaslab_free() directly. This avoids the CPU cost of allocating the zio_t, and more importantly the cost of adding and later removing this zio_t from the parent zio's child list. The result is that performance of background freeing more than doubles, from 0.6 million blocks per second to 1.3 million blocks per second. Reviewed-by: Paul Dagnelie <[email protected]> Reviewed-by: Serapheim Dimitropoulos <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: George Wilson <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> Closes #10034
* Fix zdb -R with 'b' flagPaul Zuchowski2020-02-101-20/+71
| | | | | | | | | | | | | zdb -R :b fails due to the indirect block being compressed, and the 'b' and 'd' flag not working in tandem when specified. Fix the flag parsing code and create a zfs test for zdb -R block display. Also fix the zio flags where the dotted notation for the vdev portion of DVA (i.e. 0.0:offset:length) fails. Reviewed-by: Ryan Moeller <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Paul Zuchowski <[email protected]> Closes #9640 Closes #9729
* Re-consolidate zio_delay_interruptMatthew Macy2020-01-211-0/+71
| | | | | | | | With recent SPL changes there is no longer any need for a per platform version. Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Matt Macy <[email protected]> Closes #9860
* Exclude data from cores unconditionally and metadata conditionallyMatthew Macy2019-12-091-2/+11
| | | | | | | | | This change allows us to align the code dump logic across platforms. Reviewed-by: Jorgen Lundman <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Matt Macy <[email protected]> Closes #9691
* Replace ASSERTV macro with compiler annotationMatthew Macy2019-12-051-2/+2
| | | | | | | | | | | Remove the ASSERTV macro and handle suppressing unused compiler warnings for variables only in ASSERTs using the __attribute__((unused)) compiler annotation. The annotation is understood by both gcc and clang. Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Jorgen Lundman <[email protected]> Signed-off-by: Matt Macy <[email protected]> Closes #9671
* Enable use of DTRACE_PROBE* macros in "spl" modulePrakash Surya2019-11-011-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | This change modifies some of the infrastructure for enabling the use of the DTRACE_PROBE* macros, such that we can use tehm in the "spl" module. Currently, when the DTRACE_PROBE* macros are used, they get expanded to create new functions, and these dynamically generated functions become part of the "zfs" module. Since the "spl" module does not depend on the "zfs" module, the use of DTRACE_PROBE* in the "spl" module would result in undefined symbols being used in the "spl" module. Specifically, DTRACE_PROBE* would turn into a function call, and the function being called would be a symbol only contained in the "zfs" module; which results in a linker and/or runtime error. Thus, this change adds the necessary logic to the "spl" module, to mirror the tracing functionality available to the "zfs" module. After this change, we'll have a "trace_zfs.h" header file which defines the probes available only to the "zfs" module, and a "trace_spl.h" header file which defines the probes available only to the "spl" module. Reviewed by: Brad Lewis <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Prakash Surya <[email protected]> Closes #9525
* Move zio_delay_interrupt to platform codeMatthew Macy2019-10-131-71/+0
| | | | | | | | FreeBSD has its own implementation as do other platforms. Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Ryan Moeller <[email protected]> Signed-off-by: Matt Macy <[email protected]> Closes #9439
* OpenZFS restructuring - move linux tracing code to platform directoriesMatthew Macy2019-09-111-1/+1
| | | | | | | | | | | Move Linux specific tracing headers and source to platform directories and update the build system. Reviewed-by: Allan Jude <[email protected]> Reviewed-by: Ryan Moeller <[email protected]> Reviewed by: Brad Lewis <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Matt Macy <[email protected]> Closes #9290
* Make module tunables cross platformMatthew Macy2019-09-051-16/+10
| | | | | | | | | | | Adds ZFS_MODULE_PARAM to abstract module parameter setting to operating systems other than Linux. Reviewed-by: Jorgen Lundman <[email protected]> Reviewed-by: Igor Kozhukhov <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Matt Macy <[email protected]> Signed-off-by: Ryan Moeller <[email protected]> Closes #9230
* Prevent race in blkptr_verify against device removalPaul Dagnelie2019-08-131-5/+11
| | | | | | | | | | | | | | | | | When we check the vdev of the blkptr in zfs_blkptr_verify, we can run into a race condition where that vdev is temporarily unavailable. This happens when a device removal operation and the old vdev_t has been removed from the array, but the new indirect vdev has not yet been inserted. We hold the spa_config_lock while doing our sensitive verification. To ensure that we don't deadlock, we only grab the lock if we don't have config_writer held. In addition, I had to const the tags of the refcounts and the spa_config_lock arguments. Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Serapheim Dimitropoulos <[email protected]> Signed-off-by: Paul Dagnelie <[email protected]> Closes #9112
* Log Spacemap ProjectSerapheim Dimitropoulos2019-07-161-3/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | = Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent db587941c5ff6dea01932bb78f70db63cf7f38ba Update vdev_is_spacemap_addressable() for new spacemap encoding 419ba5914552c6185afbe1dd17b3ed4b0d526547 Simplify spa_sync by breaking it up to smaller functions 8dc2197b7b1e4d7ebc1420ea30e51c6541f1d834 Factor metaslab_load_wait() in metaslab_load() b194fab0fb6caad18711abccaff3c69ad8b3f6d3 Rename range_tree_verify to range_tree_verify_not_present df72b8bebe0ebac0b20e0750984bad182cb6564a Change target size of metaslabs from 256GB to 16GB c853f382db731e15a87512f4ef1101d14d778a55 zdb -L should skip leak detection altogether 21e7cf5da89f55ce98ec1115726b150e19eefe89 vs_alloc can underflow in L2ARC vdevs 7558997d2f808368867ca7e5234e5793446e8f3f Simplify log vdev removal code 6c926f426a26ffb6d7d8e563e33fc176164175cb Get rid of space_map_update() for ms_synced_length 425d3237ee88abc53d8522a7139c926d278b4b7f Introduce auxiliary metaslab histograms 928e8ad47d3478a3d5d01f0dd6ae74a9371af65e Error path in metaslab_load_impl() forgets to drop ms_sync_lock 8eef997679ba54547f7d361553d21b3291f41ae7 = References Background, Motivation, and Internals of the Feature - OpenZFS 2017 Presentation: youtu.be/jj2IxRkl5bQ - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemaps-project Flushing Algorithm Internals & Performance Results (Illumos Specific) - Blogpost: sdimitro.github.io/post/zfs-lsm-flushing/ - OpenZFS 2018 Presentation: youtu.be/x6D2dHRjkxw - Slides: slideshare.net/SerapheimNikolaosDim/zfs-log-spacemap-flushing-algorithm Upstream Delphix Issues: DLPX-51539, DLPX-59659, DLPX-57783, DLPX-61438, DLPX-41227, DLPX-59320 DLPX-63385 Reviewed-by: Sean Eric Fagan <[email protected]> Reviewed-by: Matt Ahrens <[email protected]> Reviewed-by: George Wilson <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes #8442
* nopwrites on dmu_sync-ed blocks can result in a panicGeorge Wilson2019-06-281-0/+14
| | | | | | | | | | | | | | | | | After device removal, performing nopwrites on a dmu_sync-ed block will result in a panic. This panic can show up in two ways: 1. an attempt to issue an IOCTL in vdev_indirect_io_start() 2. a failed comparison of zio->io_bp and zio->io_bp_orig in zio_done() To resolve both of these panics, nopwrites of blocks on indirect vdevs should be ignored and new allocations should be performed on concrete vdevs. Reviewed-by: Igor Kozhukhov <[email protected]> Reviewed-by: Pavel Zakharov <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: George Wilson <[email protected]> Closes #8957
* Fix bp_embedded_type enum definitionloli10K2019-06-241-1/+1
| | | | | | | | | | With the addition of BP_EMBEDDED_TYPE_REDACTED in 30af21b0 a couple of codepaths make wrong assumptions and could potentially result in errors. Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Chris Dunlop <[email protected]> Reviewed-by: Paul Dagnelie <[email protected]> Signed-off-by: loli10K <[email protected]> Closes #8951
* dedup=verify doesn't clear the blkptr's dedup flagMatthew Ahrens2019-06-201-0/+2
| | | | | | | | | | | | The logic to handle strong checksum collisions where the data doesn't match is incorrect. It is not clearing the dedup bit of the blkptr, which can cause a panic later in zio_ddt_free() due to the dedup table not matching what is in the blkptr. Reviewed-by: Tom Caputi <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> External-issue: DLPX-48097 Closes #8936
* Remove dedupditto functionalityMatthew Ahrens2019-06-191-68/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If dedup is in use, the `dedupditto` property can be set, causing ZFS to keep an extra copy of data that is referenced many times (>100x). The idea was that this data is more important than other data and thus we want to be really sure that it is not lost if the disk experiences a small amount of random corruption. ZFS (and system administrators) rely on the pool-level redundancy to protect their data (e.g. mirroring or RAIDZ). Since the user/sysadmin doesn't have control over what data will be offered extra redundancy by dedupditto, this extra redundancy is not very useful. The bulk of the data is still vulnerable to loss based on the pool-level redundancy. For example, if particle strikes corrupt 0.1% of blocks, you will either be saved by mirror/raidz, or you will be sad. This is true even if dedupditto saved another 0.01% of blocks from being corrupted. Therefore, the dedupditto functionality is rarely enabled (i.e. the property is rarely set), and it fulfills its promise of increased redundancy even more rarely. Additionally, this feature does not work as advertised (on existing releases), because scrub/resilver did not repair the extra (dedupditto) copy (see https://github.com/zfsonlinux/zfs/pull/8270). In summary, this seldom-used feature doesn't work, and even if it did it wouldn't provide useful data protection. It has a non-trivial maintenance burden (again see https://github.com/zfsonlinux/zfs/pull/8270). We should remove the dedupditto functionality. For backwards compatibility with the existing CLI, "zpool set dedupditto" will still "succeed" (exit code zero), but won't have any effect. For backwards compatibility with existing pools that had dedupditto enabled at some point, the code will still be able to understand dedupditto blocks and free them when appropriate. However, ZFS won't write any new dedupditto blocks. Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Igor Kozhukhov <[email protected]> Reviewed-by: Alek Pinchuk <[email protected]> Issue #8270 Closes #8310
* Implement Redacted Send/ReceivePaul Dagnelie2019-06-191-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Redacted send/receive allows users to send subsets of their data to a target system. One possible use case for this feature is to not transmit sensitive information to a data warehousing, test/dev, or analytics environment. Another is to save space by not replicating unimportant data within a given dataset, for example in backup tools like zrepl. Redacted send/receive is a three-stage process. First, a clone (or clones) is made of the snapshot to be sent to the target. In this clone (or clones), all unnecessary or unwanted data is removed or modified. This clone is then snapshotted to create the "redaction snapshot" (or snapshots). Second, the new zfs redact command is used to create a redaction bookmark. The redaction bookmark stores the list of blocks in a snapshot that were modified by the redaction snapshot(s). Finally, the redaction bookmark is passed as a parameter to zfs send. When sending to the snapshot that was redacted, the redaction bookmark is used to filter out blocks that contain sensitive or unwanted information, and those blocks are not included in the send stream. When sending from the redaction bookmark, the blocks it contains are considered as candidate blocks in addition to those blocks in the destination snapshot that were modified since the creation_txg of the redaction bookmark. This step is necessary to allow the target to rehydrate data in the case where some blocks are accidentally or unnecessarily modified in the redaction snapshot. The changes to bookmarks to enable fast space estimation involve adding deadlists to bookmarks. There is also logic to manage the life cycles of these deadlists. The new size estimation process operates in cases where previously an accurate estimate could not be provided. In those cases, a send is performed where no data blocks are read, reducing the runtime significantly and providing a byte-accurate size estimate. Reviewed-by: Dan Kimmel <[email protected]> Reviewed-by: Matt Ahrens <[email protected]> Reviewed-by: Prashanth Sreenivasa <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: George Wilson <[email protected]> Reviewed-by: Chris Williamson <[email protected]> Reviewed-by: Pavel Zhakarov <[email protected]> Reviewed-by: Sebastien Roy <[email protected]> Reviewed-by: Prakash Surya <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Paul Dagnelie <[email protected]> Closes #7958
* compress metadata in later sync passesMatthew Ahrens2019-06-131-2/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Starting in sync pass 5 (zfs_sync_pass_dont_compress), we disable compression (including of metadata). Ostensibly this helps the sync passes to converge (i.e. for a sync pass to not need to allocate anything because it is 100% overwrites). However, in practice it increases the average number of sync passes, because when we turn compression off, a lot of block's size will change and thus we have to re-allocate (not overwrite) them. It also increases the number of 128KB allocations (e.g. for indirect blocks and spacemaps) because these will not be compressed. The 128K allocations are especially detrimental to performance on highly fragmented systems, which may have very few free segments of this size, and may need to load new metaslabs to satisfy 128K allocations. We should increase zfs_sync_pass_dont_compress. In practice on a highly fragmented system we see a few 5-pass txg's, a tiny number of 6-pass txg's, and no txg's with more than 6 passes. Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Richard Elling <[email protected]> Reviewed by: Pavel Zakharov <[email protected]> Reviewed-by: Serapheim Dimitropoulos <[email protected]> Reviewed-by: George Wilson <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> External-issue: DLPX-63431 Closes #8892
* single-chunk scatter ABDs can be treated as linearMatthew Ahrens2019-06-111-6/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Scatter ABD's are allocated from a number of pages. In contrast to linear ABD's, these pages are disjoint in the kernel's virtual address space, so they can't be accessed as a contiguous buffer. Therefore routines that need a linear buffer (e.g. abd_borrow_buf() and friends) must allocate a separate linear buffer (with zio_buf_alloc()), and copy the contents of the pages to/from the linear buffer. This can have a measurable performance overhead on some workloads. https://github.com/zfsonlinux/zfs/commit/87c25d567fb7969b44c7d8af63990e ("abd_alloc should use scatter for >1K allocations") increased the use of scatter ABD's, specifically switching 1.5K through 4K (inclusive) buffers from linear to scatter. For workloads that access blocks whose compressed sizes are in this range, that commit introduced an additional copy into the read code path. For example, the sequential_reads_arc_cached tests in the test suite were reduced by around 5% (this is doing reads of 8K-logical blocks, compressed to 3K, which are cached in the ARC). This commit treats single-chunk scattered buffers as linear buffers, because they are contiguous in the kernel's virtual address space. All single-page (4K) ABD's can be represented this way. Some multi-page ABD's can also be represented this way, if we were able to allocate a single "chunk" (higher-order "page" which represents a power-of-2 series of physically-contiguous pages). This is often the case for 2-page (8K) ABD's. Representing a single-entry scatter ABD as a linear ABD has the performance advantage of avoiding the copy (and allocation) in abd_borrow_buf_copy / abd_return_buf_copy. A performance increase of around 5% has been observed for ARC-cached reads (of small blocks which can take advantage of this), fixing the regression introduced by 87c25d567. Note that this optimization is only possible because all physical memory is always mapped into the kernel's address space. This is not the case for HIGHMEM pages, so the optimization can not be made on 32-bit systems. Reviewed-by: Chunwei Chen <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> Closes #8580
* Restrict kstats and print real pointersSara Hartse2019-04-041-2/+2
| | | | | | | | | | | | | | | There are several places where we use zfs_dbgmsg and %p to print pointers. In the Linux kernel, these values obfuscated to prevent information leaks which means the pointers aren't very useful for debugging crash dumps. We decided to restrict the permissions of dbgmsg (and some other kstats while we were at it) and print pointers with %px in zfs_dbgmsg as well as spl_dumpstack Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: John Gallagher <[email protected]> Signed-off-by: sara hartse <[email protected]> Closes #8467 Closes #8476
* Add TRIM supportBrian Behlendorf2019-03-291-9/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <[email protected]> Reviewed-by: Tim Chase <[email protected]> Reviewed-by: Matt Ahrens <[email protected]> Reviewed-by: George Wilson <[email protected]> Reviewed-by: Serapheim Dimitropoulos <[email protected]> Contributions-by: Saso Kiselkov <[email protected]> Contributions-by: Tim Chase <[email protected]> Contributions-by: Chunwei Chen <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #8419 Closes #598
* Make zpool status counters match error events countTony Hutter2019-03-141-1/+14
| | | | | | | | | | | | | | | | | | | The number of IO and checksum events should match the number of errors seen in zpool status. Previously there was a mismatch between the two counts because zpool status would only count unrecovered errors, while zpool events would get an event for *all* errors (recovered or not). This lead to situations where disks could be faulted for "too many errors", while at the same time showing zero errors in zpool status. This fixes the zpool status error counters to increment at the same times we post the error events. Reviewed-by: Tom Caputi <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Olaf Faaland <[email protected]> Signed-off-by: Tony Hutter <[email protected]> Closes #4851 Closes #7817
* Delay injection can cause indefinitely hung ziosSara Hartse2019-02-151-0/+1
| | | | | | | | | | | If we hit the (NSEC_TO_TICK(diff) == 0) condition in zio_delay_interrupt, zio_interrupt is never called and the zio does not progress. Reviewed by: Matt Ahrens <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: George Melikov <[email protected]> Signed-off-by: sara hartse <[email protected]> Closes #8404
* zio_deadman_impl() fix and enhancementTim Chase2019-02-151-9/+14
| | | | | | | | | | | | | Add the zio_deadman_log_all tunable to print all zios in zio_deadman_impl(). Also, in all cases, display the depth of the zio relative to the original parent zio. This is meant to be used by developers to gain diagnostic information for hangs which don't involve fully set-up zio trees or are otherwise stuck or hung in an early stage. Reviewed-by: Olaf Faaland <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: loli10K <[email protected]> Signed-off-by: Tim Chase <[email protected]> Closes #8362
* Minor spelling correctionsBrian Behlendorf2019-01-131-3/+3
| | | | | | | | | | Some minor spelling mistakes and typos. No functional changes. Reviewed-by: Neal Gompa <[email protected]> Reviewed by: Matt Ahrens <[email protected]> Reviewed-by: Giuseppe Di Natale <[email protected]> Reviewed-by: bunder2015 <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #8272
* OpenZFS 9993 - zil writes can get delayed in zio pipelineGeorge Wilson2018-12-071-1/+2
| | | | | | | | | | | | | | | Authored by: George Wilson <[email protected]> Reviewed by: Prakash Surya <[email protected]> Reviewed by: Brad Lewis <[email protected]> Reviewed by: Matt Ahrens <[email protected]> Reviewed by: Tom Caputi <[email protected]> Reviewed by: George Melikov <[email protected]> Approved by: Dan McDonald <[email protected]> Ported-by: Brian Behlendorf <[email protected]> OpenZFS-issue: https://www.illumos.org/issues/9993 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2258ad0b Closes #8185
* Add zpool status -s (slow I/Os) and -p (parseable)Tony Hutter2018-11-081-7/+27
| | | | | | | | | | | | | | | | | | This patch adds a new slow I/Os (-s) column to zpool status to show the number of VDEV slow I/Os. This is the number of I/Os that didn't complete in zio_slow_io_ms milliseconds. It also adds a new parsable (-p) flag to display exact values. NAME STATE READ WRITE CKSUM SLOW testpool ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - loop0 ONLINE 0 0 0 20 loop1 ONLINE 0 0 0 0 Reviewed-by: Brian Behlendorf <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Signed-off-by: Tony Hutter <[email protected]> Closes #7756 Closes #6885
* OpenZFS 9677 - panic from zio_write_gang_block()Brad Lewis2018-10-031-6/+14
| | | | | | | | | | | | | | | | Panic from zio_write_gang_block() when creating dump device on fragmented rpool. Authored by: Brad Lewis <[email protected]> Reviewed by: Matt Ahrens <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Prashanth Sreenivasa <[email protected]> Approved by: Robert Mustacchi <[email protected]> Ported-by: Behlendorf <[email protected]> OpenZFS-issue: https://illumos.org/issues/9677 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7341a7d Closes #7975
* Prefix all refcount functions with zfs_Tim Schumacher2018-10-011-2/+2
| | | | | | | | | | | | Recent changes in the Linux kernel made it necessary to prefix the refcount_add() function with zfs_ due to a name collision. To bring the other functions in line with that and to avoid future collisions, prefix the other refcount functions as well. Reviewed by: Matthew Ahrens <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Tim Schumacher <[email protected]> Closes #7963
* Pool allocation classesDon Brady2018-09-051-19/+79
| | | | | | | | | | | | | | | | | | | | Allocation Classes add the ability to have allocation classes in a pool that are dedicated to serving specific block categories, such as DDT data, metadata, and small file blocks. A pool can opt-in to this feature by adding a 'special' or 'dedup' top-level VDEV. Reviewed by: Pavel Zakharov <[email protected]> Reviewed-by: Richard Laager <[email protected]> Reviewed-by: Alek Pinchuk <[email protected]> Reviewed-by: Håkan Johansson <[email protected]> Reviewed-by: Andreas Dilger <[email protected]> Reviewed-by: DHE <[email protected]> Reviewed-by: Richard Elling <[email protected]> Reviewed-by: Gregor Kopka <[email protected]> Reviewed-by: Kash Pande <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Matthew Ahrens <[email protected]> Signed-off-by: Don Brady <[email protected]> Closes #5182
* OpenZFS 9403 - assertion failed in arc_buf_destroy()Tom Caputi2018-08-291-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Assertion failed in arc_buf_destroy() when concurrently reading block with checksum error. Porting notes: * The ability to zinject decompression errors has been added, but this only works at the zio_decompress() level, where we have all of the info we need to match against the user's zinject options. * The decompress_fault test has been added to test the new zinject functionality * We attempted to set zio_decompress_fail_fraction to (1 << 18) in ztest for further test coverage. Although this did uncover a few low priority issues, this unfortuantely also causes ztest to ASSERT in many locations where the code is working correctly since it is designed to fail on IO errors. Developers can manually set this variable with the '-o' option to find and debug issues. Authored by: Matt Ahrens <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Paul Dagnelie <[email protected]> Reviewed by: Pavel Zakharov <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Approved by: Matt Ahrens <[email protected]> Ported-by: Tom Caputi <[email protected]> OpenZFS-issue: https://illumos.org/issues/9403 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/fa98e487a9 Closes #7822
* Reduce taskq and context-switch cost of zio pipeMatthew Ahrens2018-08-021-124/+144
| | | | | | | | | | | | | | | | | | | | When doing a read from disk, ZFS creates 3 ZIO's: a zio_null(), the logical zio_read(), and then a physical zio. Currently, each of these results in a separate taskq_dispatch(zio_execute). On high-read-iops workloads, this causes a significant performance impact. By processing all 3 ZIO's in a single taskq entry, we reduce the overhead on taskq locking and context switching. We accomplish this by allowing zio_done() to return a "next zio to execute" to zio_execute(). This results in a ~12% performance increase for random reads, from 96,000 iops to 108,000 iops (with recordsize=8k, on SSD's). Reviewed by: Pavel Zakharov <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed by: George Wilson <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> External-issue: DLPX-59292 Closes #7736
* OpenZFS 9112 - Improve allocation performance on high-end systemsPaul Dagnelie2018-07-311-32/+56
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Overview ======== We parallelize the allocation process by creating the concept of "allocators". There are a certain number of allocators per metaslab group, defined by the value of a tunable at pool open time. Each allocator for a given metaslab group has up to 2 active metaslabs; one "primary", and one "secondary". The primary and secondary weight mean the same thing they did in in the pre-allocator world; primary metaslabs are used for most allocations, secondary metaslabs are used for ditto blocks being allocated in the same metaslab group. There is also the CLAIM weight, which has been separated out from the other weights, but that is less important to understanding the patch. The active metaslabs for each allocator are moved from their normal place in the metaslab tree for the group to the back of the tree. This way, they will not be selected for use by other allocators searching for new metaslabs unless all the passive metaslabs are unsuitable for allocations. If that does happen, the allocators will "steal" from each other to ensure that IOs don't fail until there is truly no space left to perform allocations. In addition, the alloc queue for each metaslab group has been broken into a separate queue for each allocator. We don't want to dramatically increase the number of inflight IOs on low-end systems, because it can significantly increase txg times. On the other hand, we want to ensure that there are enough IOs for each allocator to allow for good coalescing before sending the IOs to the disk. As a result, we take a compromise path; each allocator's alloc queue max depth starts at a certain value for every txg. Every time an IO completes, we increase the max depth. This should hopefully provide a good balance between the two failure modes, while not dramatically increasing complexity. We also parallelize the spa_alloc_tree and spa_alloc_lock, which cause very similar contention when selecting IOs to allocate. This parallelization uses the same allocator scheme as metaslab selection. Performance Results =================== Performance improvements from this change can vary significantly based on the number of CPUs in the system, whether or not the system has a NUMA architecture, the speed of the drives, the values for the various tunables, and the workload being performed. For an fio async sequential write workload on a 24 core NUMA system with 256 GB of RAM and 8 128 GB SSDs, there is a roughly 25% performance improvement. Future Work =========== Analysis of the performance of the system with this patch applied shows that a significant new bottleneck is the vdev disk queues, which also need to be parallelized. Prototyping of this change has occurred, and there was a performance improvement, but more work needs to be done before its stability has been verified and it is ready to be upstreamed. Authored by: Paul Dagnelie <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Serapheim Dimitropoulos <[email protected]> Reviewed by: Alexander Motin <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Approved by: Gordon Ross <[email protected]> Ported-by: Paul Dagnelie <[email protected]> Signed-off-by: Paul Dagnelie <[email protected]> Porting Notes: * Fix reservation test failures by increasing tolerance. OpenZFS-issue: https://illumos.org/issues/9112 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/3f3cc3c3 Closes #7682
* OpenZFS 9166 - zfs storage pool checkpointSerapheim Dimitropoulos2018-06-261-14/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Details about the motivation of this feature and its usage can be found in this blogpost: https://sdimitro.github.io/post/zpool-checkpoint/ A lightning talk of this feature can be found here: https://www.youtube.com/watch?v=fPQA8K40jAM Implementation details can be found in big block comment of spa_checkpoint.c Side-changes that are relevant to this commit but not explained elsewhere: * renames members of "struct metaslab trees to be shorter without losing meaning * space_map_{alloc,truncate}() accept a block size as a parameter. The reason is that in the current state all space maps that we allocate through the DMU use a global tunable (space_map_blksz) which defauls to 4KB. This is ok for metaslab space maps in terms of bandwirdth since they are scattered all over the disk. But for other space maps this default is probably not what we want. Examples are device removal's vdev_obsolete_sm or vdev_chedkpoint_sm from this review. Both of these have a 1:1 relationship with each vdev and could benefit from a bigger block size. Porting notes: * The part of dsl_scan_sync() which handles async destroys has been moved into the new dsl_process_async_destroys() function. * Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write to block device backed pools. * ZTS: * Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg". * Don't use large dd block sizes on /dev/urandom under Linux in checkpoint_capacity. * Adopt Delphix-OS's setting of 4 (spa_asize_inflation = SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed its attempts to fill the pool * Create the base and nested pools with sync=disabled to speed up the "setup" phase. * Clear labels in test pool between checkpoint tests to avoid duplicate pool issues. * The import_rewind_device_replaced test has been marked as "known to fail" for the reasons listed in its DISCLAIMER. * New module parameters: zfs_spa_discard_memory_limit, zfs_remove_max_bytes_pause (not documented - debugging only) vdev_max_ms_count (formerly metaslabs_per_vdev) vdev_min_ms_count Authored by: Serapheim Dimitropoulos <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: John Kennedy <[email protected]> Reviewed by: Dan Kimmel <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Approved by: Richard Lowe <[email protected]> Ported-by: Tim Chase <[email protected]> Signed-off-by: Tim Chase <[email protected]> OpenZFS-issue: https://illumos.org/issues/9166 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8 Closes #7570
* Update build system and packagingBrian Behlendorf2018-05-291-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Minimal changes required to integrate the SPL sources in to the ZFS repository build infrastructure and packaging. Build system and packaging: * Renamed SPL_* autoconf m4 macros to ZFS_*. * Removed redundant SPL_* autoconf m4 macros. * Updated the RPM spec files to remove SPL package dependency. * The zfs package obsoletes the spl package, and the zfs-kmod package obsoletes the spl-kmod package. * The zfs-kmod-devel* packages were updated to add compatibility symlinks under /usr/src/spl-x.y.z until all dependent packages can be updated. They will be removed in a future release. * Updated copy-builtin script for in-kernel builds. * Updated DKMS package to include the spl.ko. * Updated stale AUTHORS file to include all contributors. * Updated stale COPYRIGHT and included the SPL as an exception. * Renamed README.markdown to README.md * Renamed OPENSOLARIS.LICENSE to LICENSE. * Renamed DISCLAIMER to NOTICE. Required code changes: * Removed redundant HAVE_SPL macro. * Removed _BOOT from nvpairs since it doesn't apply for Linux. * Initial header cleanup (removal of empty headers, refactoring). * Remove SPL repository clone/build from zimport.sh. * Use of DEFINE_RATELIMIT_STATE and DEFINE_SPINLOCK removed due to build issues when forcing C99 compilation. * Replaced legacy ACCESS_ONCE with READ_ONCE. * Include needed headers for `current` and `EXPORT_SYMBOL`. Reviewed-by: Tony Hutter <[email protected]> Reviewed-by: Olaf Faaland <[email protected]> Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: Pavel Zakharov <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> TEST_ZIMPORT_SKIP="yes" Closes #7556
* OpenZFS 9075 - Improve ZFS pool import/load process and corrupted pool recoveryPavel Zakharov2018-05-081-4/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Some work has been done lately to improve the debugability of the ZFS pool load (and import) process. This includes: 7638 Refactor spa_load_impl into several functions 8961 SPA load/import should tell us why it failed 7277 zdb should be able to print zfs_dbgmsg's To iterate on top of that, there's a few changes that were made to make the import process more resilient and crash free. One of the first tasks during the pool load process is to parse a config provided from userland that describes what devices the pool is composed of. A vdev tree is generated from that config, and then all the vdevs are opened. The Meta Object Set (MOS) of the pool is accessed, and several metadata objects that are necessary to load the pool are read. The exact configuration of the pool is also stored inside the MOS. Since the configuration provided from userland is external and might not accurately describe the vdev tree of the pool at the txg that is being loaded, it cannot be relied upon to safely operate the pool. For that reason, the configuration in the MOS is read early on. In the past, the two configurations were compared together and if there was a mismatch then the load process was aborted and an error was returned. The latter was a good way to ensure a pool does not get corrupted, however it made the pool load process needlessly fragile in cases where the vdev configuration changed or the userland configuration was outdated. Since the MOS is stored in 3 copies, the configuration provided by userland doesn't have to be perfect in order to read its contents. Hence, a new approach has been adopted: The pool is first opened with the untrusted userland configuration just so that the real configuration can be read from the MOS. The trusted MOS configuration is then used to generate a new vdev tree and the pool is re-opened. When the pool is opened with an untrusted configuration, writes are disabled to avoid accidentally damaging it. During reads, some sanity checks are performed on block pointers to see if each DVA points to a known vdev; when the configuration is untrusted, instead of panicking the system if those checks fail we simply avoid issuing reads to the invalid DVAs. This new two-step pool load process now allows rewinding pools accross vdev tree changes such as device replacement, addition, etc. Loading a pool from an external config file in a clustering environment also becomes much safer now since the pool will import even if the config is outdated and didn't, for instance, register a recent device addition. With this code in place, it became relatively easy to implement a long-sought-after feature: the ability to import a pool with missing top level (i.e. non-redundant) devices. Note that since this almost guarantees some loss of data, this feature is for now restricted to a read-only import. Porting notes (ZTS): * Fix 'make dist' target in zpool_import * The maximum path length allowed by tar is 99 characters. Several of the new test cases exceeded this limit resulting in them not being included in the tarball. Shorten the names slightly. * Set/get tunables using accessor functions. * Get last synced txg via the "zfs_txg_history" mechanism. * Clear zinject handlers in cleanup for import_cache_device_replaced and import_rewind_device_replaced in order that the zpool can be exported if there is an error. * Increase FILESIZE to 8G in zfs-test.sh to allow for a larger ext4 file system to be created on ZFS_DISK2. Also, there's no need to partition ZFS_DISK2 at all. The partitioning had already been disabled for multipath devices. Among other things, the partitioning steals some space from the ext4 file system, makes it difficult to accurately calculate the paramters to parted and can make some of the tests fail. * Increase FS_SIZE and FILE_SIZE in the zpool_import test configuration now that FILESIZE is larger. * Write more data in order that device evacuation take lonnger in a couple tests. * Use mkdir -p to avoid errors when the directory already exists. * Remove use of sudo in import_rewind_config_changed. Authored by: Pavel Zakharov <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Andrew Stormont <[email protected]> Approved by: Hans Rosenfeld <[email protected]> Ported-by: Tim Chase <[email protected]> Signed-off-by: Tim Chase <[email protected]> OpenZFS-issue: https://illumos.org/issues/9075 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/619c0123 Closes #7459
* Add support for decryption faults in zinjectTom Caputi2018-05-021-5/+16
| | | | | | | | | | | | | | This patch adds the ability for zinject to trigger decryption and authentication faults in the ZIO and ARC layers. This functionality is exposed via the new "decrypt" error type, which may be provided for "data" object types. This patch also refactors some of the core encryption / decryption functions so that they have consistent prototypes, handle errors consistently, and do not have unused arguments. Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Tom Caputi <[email protected]> Closes #7474
* OpenZFS 9236 - nuke spa_dbgmsgMatthew Ahrens2018-04-301-1/+1
| | | | | | | | | | | | | | | | | | | | | | | We should use zfs_dbgmsg instead of spa_dbgmsg. Or at least, metaslab_condense() should call zfs_dbgmsg because it's important and rare enough to always log. It's possible that the message in zio_dva_allocate() would be too high-frequency for zfs_dbgmsg. Authored by: Matthew Ahrens <[email protected]> Reviewed by: Serapheim Dimitropoulos <[email protected]> Reviewed by: Pavel Zakharov <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Richard Elling <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Approved by: Richard Lowe <[email protected]> Ported-by: Giuseppe Di Natale <[email protected]> Patch Notes: * Removed ZFS_DEBUG_SPA from zfs-module-parameters.5 OpenZFS-issue: https://www.illumos.org/issues/9236 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/cfaba7f668 Closes #7467
* OpenZFS 9290 - device removal reduces redundancy of mirrorsMatthew Ahrens2018-04-141-21/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Mirrors are supposed to provide redundancy in the face of whole-disk failure and silent damage (e.g. some data on disk is not right, but ZFS hasn't detected the whole device as being broken). However, the current device removal implementation bypasses some of the mirror's redundancy. Note that in no case is incorrect data returned, but we might get a checksum error when we should have been able to find the right data. There are two underlying problems: 1. When we remove a mirror device, we only read one side of the mirror. Since we can't verify the checksum, this side may be silently bad, but the good data is on the other side of the mirror (which we didn't read). This can cause the removal to "bake in" the busted data – all copies of the data in the new location are the same, busted version, while we left the good version behind. The fix for this is to read and copy both sides of the mirror. If the old and new vdevs are mirrors, we will read both sides of the old mirror, and write each copy to the corresponding side of the new mirror. (If the old and new vdevs have a different number of children, we will do this as best as possible.) Even though we aren't verifying checksums, this ensures that as long as there's a good copy of the data, we'll have a good copy after the removal, even if there's silent damage to one side of the mirror. If we're removing a mirror that has some silent damage, we'll have exactly the same damage in the new location (assuming that the new location is also a mirror). 2. When we read from an indirect vdev that points to a mirror vdev, we only consider one copy of the data. This can lead to reduced effective redundancy, because we might read a bad copy of the data from one side of the mirror, and not retry the other, good side of the mirror. Note that the problem is not with the removal process, but rather after the removal has completed (having copied correct data to both sides of the mirror), if one side of the new mirror is silently damaged, we encounter the problem when reading the relocated data via the indirect vdev. Also note that the problem doesn't occur when ZFS knows that one side of the mirror is bad, e.g. when a disk entirely fails or is offlined. The impact is that reads (from indirect vdevs that point to mirrors) may return a checksum error even though the good data exists on one side of the mirror, and scrub doesn't repair all data on the mirror (if some of it is pointed to via an indirect vdev). The fix for this is complicated by "split blocks" - one logical block may be split into two (or more) pieces with each piece moved to a different new location. In this case we need to read all versions of each split (one from each side of the mirror), and figure out which combination of versions results in the correct checksum, and then repair the incorrect versions. This ensures that we supply the same redundancy whether you use device removal or not. For example, if a mirror has small silent errors on all of its children, we can still reconstruct the correct data, as long as those errors are at sufficiently-separated offsets (specifically, separated by the largest block size - default of 128KB, but up to 16MB). Porting notes: * A new indirect vdev check was moved from dsl_scan_needs_resilver_cb() to dsl_scan_needs_resilver(), which was added to ZoL as part of the sequential scrub work. * Passed NULL for zfs_ereport_post_checksum()'s zbookmark_phys_t parameter. The extra parameter is unique to ZoL. * When posting indirect checksum errors the ABD can be passed directly, zfs_ereport_post_checksum() is not yet ABD-aware in OpenZFS. Authored by: Matthew Ahrens <[email protected]> Reviewed by: Tim Chase <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Ported-by: Tim Chase <[email protected]> OpenZFS-issue: https://illumos.org/issues/9290 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/591 Closes #6900
* OpenZFS 7614, 9064 - zfs device evacuation/removalMatthew Ahrens2018-04-141-5/+41
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | OpenZFS 7614 - zfs device evacuation/removal OpenZFS 9064 - remove_mirror should wait for device removal to complete This project allows top-level vdevs to be removed from the storage pool with "zpool remove", reducing the total amount of storage in the pool. This operation copies all allocated regions of the device to be removed onto other devices, recording the mapping from old to new location. After the removal is complete, read and free operations to the removed (now "indirect") vdev must be remapped and performed at the new location on disk. The indirect mapping table is kept in memory whenever the pool is loaded, so there is minimal performance overhead when doing operations on the indirect vdev. The size of the in-memory mapping table will be reduced when its entries become "obsolete" because they are no longer used by any block pointers in the pool. An entry becomes obsolete when all the blocks that use it are freed. An entry can also become obsolete when all the snapshots that reference it are deleted, and the block pointers that reference it have been "remapped" in all filesystems/zvols (and clones). Whenever an indirect block is written, all the block pointers in it will be "remapped" to their new (concrete) locations if possible. This process can be accelerated by using the "zfs remap" command to proactively rewrite all indirect blocks that reference indirect (removed) vdevs. Note that when a device is removed, we do not verify the checksum of the data that is copied. This makes the process much faster, but if it were used on redundant vdevs (i.e. mirror or raidz vdevs), it would be possible to copy the wrong data, when we have the correct data on e.g. the other side of the mirror. At the moment, only mirrors and simple top-level vdevs can be removed and no removal is allowed if any of the top-level vdevs are raidz. Porting Notes: * Avoid zero-sized kmem_alloc() in vdev_compact_children(). The device evacuation code adds a dependency that vdev_compact_children() be able to properly empty the vdev_child array by setting it to NULL and zeroing vdev_children. Under Linux, kmem_alloc() and related functions return a sentinel pointer rather than NULL for zero-sized allocations. * Remove comment regarding "mpt" driver where zfs_remove_max_segment is initialized to SPA_MAXBLOCKSIZE. Change zfs_condense_indirect_commit_entry_delay_ticks to zfs_condense_indirect_commit_entry_delay_ms for consistency with most other tunables in which delays are specified in ms. * ZTS changes: Use set_tunable rather than mdb Use zpool sync as appropriate Use sync_pool instead of sync Kill jobs during test_removal_with_operation to allow unmount/export Don't add non-disk names such as "mirror" or "raidz" to $DISKS Use $TEST_BASE_DIR instead of /tmp Increase HZ from 100 to 1000 which is more common on Linux removal_multiple_indirection.ksh Reduce iterations in order to not time out on the code coverage builders. removal_resume_export: Functionally, the test case is correct but there exists a race where the kernel thread hasn't been fully started yet and is not visible. Wait for up to 1 second for the removal thread to be started before giving up on it. Also, increase the amount of data copied in order that the removal not finish before the export has a chance to fail. * MMP compatibility, the concept of concrete versus non-concrete devices has slightly changed the semantics of vdev_writeable(). Update mmp_random_leaf_impl() accordingly. * Updated dbuf_remap() to handle the org.zfsonlinux:large_dnode pool feature which is not supported by OpenZFS. * Added support for new vdev removal tracepoints. * Test cases removal_with_zdb and removal_condense_export have been intentionally disabled. When run manually they pass as intended, but when running in the automated test environment they produce unreliable results on the latest Fedora release. They may work better once the upstream pool import refectoring is merged into ZoL at which point they will be re-enabled. Authored by: Matthew Ahrens <[email protected]> Reviewed-by: Alex Reece <[email protected]> Reviewed-by: George Wilson <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Prakash Surya <[email protected]> Reviewed by: Richard Laager <[email protected]> Reviewed by: Tim Chase <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Approved by: Garrett D'Amore <[email protected]> Ported-by: Tim Chase <[email protected]> Signed-off-by: Tim Chase <[email protected]> OpenZFS-issue: https://www.illumos.org/issues/7614 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f539f1eb Closes #6900
* Decryption error handling improvementsTom Caputi2018-03-311-1/+1
| | | | | | | | | | | | | | | | | | Currently, the decryption and block authentication code in the ZIO / ARC layers is a bit inconsistent with regards to the ereports that are produces and the error codes that are passed to calling functions. This patch ensures that all of these errors (which begin as ECKSUM) are converted to EIO before they leave the ZIO or ARC layer and that ereports are correctly generated on each decryption / authentication failure. In addition, this patch fixes a bug in zio_decrypt() where ECKSUM never gets written to zio->io_error. Reviewed by: Matt Ahrens <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Tom Caputi <[email protected]> Closes #7372
* Report pool suspended due to MMPOlaf Faaland2018-03-151-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | When the pool is suspended, record whether it was due to an I/O error or due to MMP writes failing to succeed within the required time. Change spa_suspended from uint8_t to zio_suspend_reason_t to store the reason. When userspace queries pool status via spa_tryimport(), report the reason the pool was suspended in a new key, ZPOOL_CONFIG_SUSPENDED_REASON. In libzfs, when interpreting the returned config nvlist, report suspension due to MMP with a new pool status enum value, ZPOOL_STATUS_IO_FAILURE_MMP. In status_callback(), which generates and emits the message when 'zpool status' is executed, add a case to print an appropriate message for the new pool status enum value. Reviewed-by: George Melikov <[email protected]> Reviewed-by: Giuseppe Di Natale <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Tony Hutter <[email protected]> Signed-off-by: Olaf Faaland <[email protected]> Closes #7296
* Raw receives must compress metadnode blocksTom Caputi2018-02-211-1/+13
| | | | | | | | | | | | | | | | | | | Currently, the DMU relies on ZIO layer compression to free LO dnode blocks that no longer have objects in them. However, raw receives disable all compression, meaning that these blocks can never be freed. In addition to the obvious space concerns, this could also cause incremental raw receives to fail to mount since the MAC of a hole is different from that of a completely zeroed block. This patch corrects this issue by adding a special case in zio_write_compress() which will attempt to compress these blocks to a hole even if ZIO_FLAG_RAW_ENCRYPT is set. This patch also removes the zfs_mdcomp_disable tunable, since tuning it could cause these same issues. Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Tom Caputi <[email protected]> Closes #7198
* OpenZFS 8857 - zio_remove_child() panic due to already destroyed parent zioGeorge Wilson2018-02-141-20/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | PROBLEM ======= It's possible for a parent zio to complete even though it has children which have not completed. This can result in the following panic: > $C ffffff01809128c0 vpanic() ffffff01809128e0 mutex_panic+0x58(fffffffffb94c904, ffffff597dde7f80) ffffff0180912950 mutex_vector_enter+0x347(ffffff597dde7f80) ffffff01809129b0 zio_remove_child+0x50(ffffff597dde7c58, ffffff32bd901ac0, ffffff3373370908) ffffff0180912a40 zio_done+0x390(ffffff32bd901ac0) ffffff0180912a70 zio_execute+0x78(ffffff32bd901ac0) ffffff0180912b30 taskq_thread+0x2d0(ffffff33bae44140) ffffff0180912b40 thread_start+8() > ::status debugging crash dump vmcore.2 (64-bit) from batfs0390 operating system: 5.11 joyent_20170911T171900Z (i86pc) image uuid: (not set) panic message: mutex_enter: bad mutex, lp=ffffff597dde7f80 owner=ffffff3c59b39480 thread=ffffff0180912c40 dump content: kernel pages only The problem is that dbuf_prefetch along with l2arc can create a zio tree which confuses the parent zio and allows it to complete with while children still exist. Here's the scenario: zio tree: pio |--- lio The parent zio, pio, has entered the zio_done stage and begins to check its children to see there are still some that have not completed. In zio_done(), the children are checked in the following order: zio_wait_for_children(zio, ZIO_CHILD_VDEV, ZIO_WAIT_DONE) zio_wait_for_children(zio, ZIO_CHILD_GANG, ZIO_WAIT_DONE) zio_wait_for_children(zio, ZIO_CHILD_DDT, ZIO_WAIT_DONE) zio_wait_for_children(zio, ZIO_CHILD_LOGICAL, ZIO_WAIT_DONE) If pio, finds any child which has not completed then it stops executing and goes to sleep. Each call to zio_wait_for_children() will grab the io_lock while checking the particular child. In this scenario, the pio has completed the first call to zio_wait_for_children() to check for any ZIO_CHILD_VDEV children. Since the only zio in the zio tree right now is the logical zio, lio, then it completes that call and prepares to check the next child type. In the meantime, the lio completes and in its callback creates a child vdev zio, cio. The zio tree looks like this: zio tree: pio |--- lio |--- cio The lio then grabs the parent's io_lock and removes itself. zio tree: pio |--- cio The pio continues to run but has already completed its check for ZIO_CHILD_VDEV and will erroneously complete. When the child zio, cio, completes it will panic the system trying to reference the parent zio which has been destroyed. SOLUTION ======== The fix is to rework the zio_wait_for_children() logic to accept a bitfield for all the children types that it's interested in checking. The io_lock will is held the entire time we check all the children types. Since the function now accepts a bitfield, a simple ZIO_CHILD_BIT() macro is provided to allow for the conversion between a ZIO_CHILD type and the bitfield used by the zio_wiat_for_children logic. Authored by: George Wilson <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: Andriy Gapon <[email protected]> Reviewed by: Youzhong Yang <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Approved by: Dan McDonald <[email protected]> Ported-by: Giuseppe Di Natale <[email protected]> OpenZFS-issue: https://www.illumos.org/issues/8857 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/862ff6d99c Issue #5918 Closes #7168
* Encryption Stability and On-Disk Format FixesTom Caputi2018-02-021-17/+33
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The on-disk format for encrypted datasets protects not only the encrypted and authenticated blocks themselves, but also the order and interpretation of these blocks. In order to make this work while maintaining the ability to do raw sends, the indirect bps maintain a secure checksum of all the MACs in the block below it along with a few other fields that determine how the data is interpreted. Unfortunately, the current on-disk format erroneously includes some fields which are not portable and thus cannot support raw sends. It is not possible to easily work around this issue due to a separate and much smaller bug which causes indirect blocks for encrypted dnodes to not be compressed, which conflicts with the previous bug. In addition, the current code generates incompatible on-disk formats on big endian and little endian systems due to an issue with how block pointers are authenticated. Finally, raw send streams do not currently include dn_maxblkid when sending both the metadnode and normal dnodes which are needed in order to ensure that we are correctly maintaining the portable objset MAC. This patch zero's out the offending fields when computing the bp MAC and ensures that these MACs are always calculated in little endian order (regardless of the host system's byte order). This patch also registers an errata for the old on-disk format, which we detect by adding a "version" field to newly created DSL Crypto Keys. We allow datasets without a version (version 0) to only be mounted for read so that they can easily be migrated. We also now include dn_maxblkid in raw send streams to ensure the MAC can be maintained correctly. This patch also contains minor bug fixes and cleanups. Reviewed-by: Jorgen Lundman <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Signed-off-by: Tom Caputi <[email protected]> Closes #6845 Closes #6864 Closes #7052
* Extend deadman logicBrian Behlendorf2018-01-251-2/+88
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <[email protected]> Reviewed by: Thomas Caputi <[email protected]> Reviewed-by: Giuseppe Di Natale <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #6999
* OpenZFS 8909 - 8585 can cause a use-after-free kernel panicPrakash Surya2017-12-281-14/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Authored by: Prakash Surya <[email protected]> Reviewed by: John Kennedy <[email protected]> Reviewed by: Matthew Ahrens <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed by: Brad Lewis <[email protected]> Reviewed by: Igor Kozhukhov <[email protected]> Reviewed by: Brian Behlendorf <[email protected]> Approved by: Robert Mustacchi <[email protected]> Ported-by: Prakash Surya <[email protected]> PROBLEM ======= There's a race condition that exists if `zil_free_lwb` races with either `zil_commit_waiter_timeout` and/or `zil_lwb_flush_vdevs_done`. Here's an example panic due to this bug: > ::status debugging crash dump vmcore.0 (64-bit) from ip-10-110-205-40 operating system: 5.11 dlpx-5.2.2.0_2017-12-04-17-28-32b6ba51fb (i86pc) image uuid: 4af0edfb-e58e-6ed8-cafc-d3e9167c7513 panic message: BAD TRAP: type=e (#pf Page fault) rp=ffffff0010555970 addr=60 occurred in module "zfs" due to a NULL pointer dereference dump content: kernel pages only > $c zio_shrink+0x12() zil_lwb_write_issue+0x30d(ffffff03dcd15cc0, ffffff03e0730e20) zil_commit_waiter_timeout+0xa2(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit_waiter+0xf3(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit+0x80(ffffff03dcd15cc0, 9a9) zfs_write+0xc34(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) fop_write+0x5b(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) write+0x250(42, fffffd7ff4832000, 2000) sys_syscall+0x177() If there's an outstanding lwb that's in `zil_commit_waiter_timeout` waiting to timeout, waiting on it's waiter's CV, we must be sure not to call `zil_free_lwb`. If we end up calling `zil_free_lwb`, then that LWB may be freed and can result in a use-after-free situation where the stale lwb pointer stored in the `zil_commit_waiter_t` structure of the thread waiting on the waiter's CV is used. A similar situation can occur if an lwb is issued to disk, and thus in the `LWB_STATE_ISSUED` state, and `zil_free_lwb` is called while the disk is servicing that lwb. In this situation, the lwb will be freed by `zil_free_lwb`, which will result in a use-after-free situation when the lwb's zio completes, and `zil_lwb_flush_vdevs_done` is called. This race condition is prevented in `zil_close` by calling `zil_commit` before `zil_free_lwb` is called, which will ensure all outstanding (i.e. all lwb's in the `LWB_STATE_OPEN` and/or `LWB_STATE_ISSUED` states) reach the `LWB_STATE_DONE` state before the lwb's are freed (`zil_commit` will not return untill all the lwb's are `LWB_STATE_DONE`). Further, this race condition is prevented in `zil_sync` by only calling `zil_free_lwb` for lwb's that do not have their `lwb_buf` pointer set. All lwb's not in the `LWB_STATE_DONE` state will have a non-null value for this pointer; the pointer is only cleared in `zil_lwb_flush_vdevs_done`, at which point the lwb's state will be changed to `LWB_STATE_DONE`. This race *is* present in `zil_suspend`, leading to this bug. At first glance, it would appear as though this would not be true because `zil_suspend` will call `zil_commit`, just like `zil_close`, but the problem is that `zil_suspend` will set the zilog's `zl_suspend` field prior to calling `zil_commit`. Further, in `zil_commit`, if `zl_suspend` is set, `zil_commit` will take a special branch of logic and use `txg_wait_synced` instead of performing the normal `zil_commit` logic. This call to `txg_wait_synced` might be good enough for the data to reach disk safely before it returns, but it does not ensure that all outstanding lwb's reach the `LWB_STATE_DONE` state before it returns. This is because, if there's an lwb "stuck" in `zil_commit_waiter_timeout`, waiting for it's lwb to timeout, it will maintain a non-null value for it's `lwb_buf` field and thus `zil_sync` will not free that lwb. Thus, even though the lwb's data is already on disk, the lwb will be left lingering, waiting on the CV, and will eventually timeout and be issued to disk even though the write is unnecessary. So, after `zil_commit` is called from `zil_suspend`, we incorrectly assume that there are not outstanding lwb's, and proceed to free all lwb's found on the zilog's lwb list. As a result, we free the lwb that will later be used `zil_commit_waiter_timeout`. SOLUTION ======== The solution to this, is to ensure all outstanding lwb's complete before calling `zil_free_lwb` via `zil_destroy` in `zil_suspend`. This patch accomplishes this goal by forcing the normal `zil_commit` logic when called from `zil_sync`. Now, `zil_suspend` will call `zil_commit_impl` which will always use the normal logic of waiting/issuing lwb's to disk before it returns. As a result, any lwb's outstanding when `zil_commit_impl` is called will be guaranteed to reach the `LWB_STATE_DONE` state by the time it returns. Further, no new lwb's will be created via `zil_commit` since the zilog's `zl_suspend` flag will be set. This will force all new callers of `zil_commit` to use `txg_wait_synced` instead of creating and issuing new lwb's. Thus, all lwb's left on the zilog's lwb list when `zil_destroy` is called will be in the `LWB_STATE_DONE` state, and we'll avoid this race condition. OpenZFS-issue: https://www.illumos.org/issues/8909 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ece62b6f8d Closes #6940
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