summaryrefslogtreecommitdiff
path: root/fs/btrfs/block-group.h
AgeCommit message (Collapse)AuthorFilesLines
2023-08-21btrfs: rename add_new_free_space() to btrfs_add_new_free_space()Filipe Manana1-2/+2
Since add_new_free_space() is exported, used outside block-group.c, rename it to include the 'btrfs_' prefix. Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-08-10btrfs: wait for actual caching progress during allocationJosef Bacik1-0/+2
Recently we've been having mysterious hangs while running generic/475 on the CI system. This turned out to be something like this: Task 1 dmsetup suspend --nolockfs -> __dm_suspend -> dm_wait_for_completion -> dm_wait_for_bios_completion -> Unable to complete because of IO's on a plug in Task 2 Task 2 wb_workfn -> wb_writeback -> blk_start_plug -> writeback_sb_inodes -> Infinite loop unable to make an allocation Task 3 cache_block_group ->read_extent_buffer_pages ->Waiting for IO to complete that can't be submitted because Task 1 suspended the DM device The problem here is that we need Task 2 to be scheduled completely for the blk plug to flush. Normally this would happen, we normally wait for the block group caching to finish (Task 3), and this schedule would result in the block plug flushing. However if there's enough free space available from the current caching to satisfy the allocation we won't actually wait for the caching to complete. This check however just checks that we have enough space, not that we can make the allocation. In this particular case we were trying to allocate 9MiB, and we had 10MiB of free space, but we didn't have 9MiB of contiguous space to allocate, and thus the allocation failed and we looped. We specifically don't cycle through the FFE loop until we stop finding cached block groups because we don't want to allocate new block groups just because we're caching, so we short circuit the normal loop once we hit LOOP_CACHING_WAIT and we found a caching block group. This is normally fine, except in this particular case where the caching thread can't make progress because the DM device has been suspended. Fix this by not only waiting for free space to >= the amount of space we want to allocate, but also that we make some progress in caching from the time we start waiting. This will keep us from busy looping when the caching is taking a while but still theoretically has enough space for us to allocate from, and fixes this particular case by forcing us to actually sleep and wait for forward progress, which will flush the plug. With this fix we're no longer hanging with generic/475. CC: stable@vger.kernel.org # 6.1+ Reviewed-by: Boris Burkov <boris@bur.io> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-07-24btrfs: remove BUG_ON()'s in add_new_free_space()Filipe Manana1-2/+2
At add_new_free_space() we have these BUG_ON()'s that are there to deal with any failure to add free space to the in memory free space cache. Such failures are mostly -ENOMEM that should be very rare. However there's no need to have these BUG_ON()'s, we can just return any error to the caller and all callers and their upper call chain are already dealing with errors. So just make add_new_free_space() return any errors, while removing the BUG_ON()'s, and returning the total amount of added free space to an optional u64 pointer argument. Reported-by: syzbot+3ba856e07b7127889d8c@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/000000000000e9cb8305ff4e8327@google.com/ Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-07-11btrfs: fix use-after-free of new block group that became unusedFilipe Manana1-0/+5
If a task creates a new block group and that block group becomes unused before we finish its creation, at btrfs_create_pending_block_groups(), then when btrfs_mark_bg_unused() is called against the block group, we assume that the block group is currently in the list of block groups to reclaim, and we move it out of the list of new block groups and into the list of unused block groups. This has two consequences: 1) We move it out of the list of new block groups associated to the current transaction. So the block group creation is not finished and if we attempt to delete the bg because it's unused, we will not find the block group item in the extent tree (or the new block group tree), its device extent items in the device tree etc, resulting in the deletion to fail due to the missing items; 2) We don't increment the reference count on the block group when we move it to the list of unused block groups, because we assumed the block group was on the list of block groups to reclaim, and in that case it already has the correct reference count. However the block group was on the list of new block groups, in which case no extra reference was taken because it's local to the current task. This later results in doing an extra reference count decrement when removing the block group from the unused list, eventually leading the reference count to 0. This second case was caught when running generic/297 from fstests, which produced the following assertion failure and stack trace: [589.559] assertion failed: refcount_read(&block_group->refs) == 1, in fs/btrfs/block-group.c:4299 [589.559] ------------[ cut here ]------------ [589.559] kernel BUG at fs/btrfs/block-group.c:4299! [589.560] invalid opcode: 0000 [#1] PREEMPT SMP PTI [589.560] CPU: 8 PID: 2819134 Comm: umount Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1 [589.560] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [589.560] RIP: 0010:btrfs_free_block_groups+0x449/0x4a0 [btrfs] [589.561] Code: 68 62 da c0 (...) [589.561] RSP: 0018:ffffa55a8c3b3d98 EFLAGS: 00010246 [589.561] RAX: 0000000000000058 RBX: ffff8f030d7f2000 RCX: 0000000000000000 [589.562] RDX: 0000000000000000 RSI: ffffffff953f0878 RDI: 00000000ffffffff [589.562] RBP: ffff8f030d7f2088 R08: 0000000000000000 R09: ffffa55a8c3b3c50 [589.562] R10: 0000000000000001 R11: 0000000000000001 R12: ffff8f05850b4c00 [589.562] R13: ffff8f030d7f2090 R14: ffff8f05850b4cd8 R15: dead000000000100 [589.563] FS: 00007f497fd2e840(0000) GS:ffff8f09dfc00000(0000) knlGS:0000000000000000 [589.563] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [589.563] CR2: 00007f497ff8ec10 CR3: 0000000271472006 CR4: 0000000000370ee0 [589.563] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [589.564] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [589.564] Call Trace: [589.564] <TASK> [589.565] ? __die_body+0x1b/0x60 [589.565] ? die+0x39/0x60 [589.565] ? do_trap+0xeb/0x110 [589.565] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs] [589.566] ? do_error_trap+0x6a/0x90 [589.566] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs] [589.566] ? exc_invalid_op+0x4e/0x70 [589.566] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs] [589.567] ? asm_exc_invalid_op+0x16/0x20 [589.567] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs] [589.567] ? btrfs_free_block_groups+0x449/0x4a0 [btrfs] [589.567] close_ctree+0x35d/0x560 [btrfs] [589.568] ? fsnotify_sb_delete+0x13e/0x1d0 [589.568] ? dispose_list+0x3a/0x50 [589.568] ? evict_inodes+0x151/0x1a0 [589.568] generic_shutdown_super+0x73/0x1a0 [589.569] kill_anon_super+0x14/0x30 [589.569] btrfs_kill_super+0x12/0x20 [btrfs] [589.569] deactivate_locked_super+0x2e/0x70 [589.569] cleanup_mnt+0x104/0x160 [589.570] task_work_run+0x56/0x90 [589.570] exit_to_user_mode_prepare+0x160/0x170 [589.570] syscall_exit_to_user_mode+0x22/0x50 [589.570] ? __x64_sys_umount+0x12/0x20 [589.571] do_syscall_64+0x48/0x90 [589.571] entry_SYSCALL_64_after_hwframe+0x72/0xdc [589.571] RIP: 0033:0x7f497ff0a567 [589.571] Code: af 98 0e (...) [589.572] RSP: 002b:00007ffc98347358 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 [589.572] RAX: 0000000000000000 RBX: 00007f49800b8264 RCX: 00007f497ff0a567 [589.572] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000557f558abfa0 [589.573] RBP: 0000557f558a6ba0 R08: 0000000000000000 R09: 00007ffc98346100 [589.573] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [589.573] R13: 0000557f558abfa0 R14: 0000557f558a6cb0 R15: 0000557f558a6dd0 [589.573] </TASK> [589.574] Modules linked in: dm_snapshot dm_thin_pool (...) [589.576] ---[ end trace 0000000000000000 ]--- Fix this by adding a runtime flag to the block group to tell that the block group is still in the list of new block groups, and therefore it should not be moved to the list of unused block groups, at btrfs_mark_bg_unused(), until the flag is cleared, when we finish the creation of the block group at btrfs_create_pending_block_groups(). Fixes: a9f189716cf1 ("btrfs: move out now unused BG from the reclaim list") CC: stable@vger.kernel.org # 5.15+ Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-06-19btrfs: update documentation for a block group's bg_list memberFilipe Manana1-1/+8
Currently we are only documenting two uses of the bg_list member of a block group, but there two more: 1) To track deleted block groups for discard purposes, introduced in commit e33e17ee1098 ("btrfs: add missing discards when unpinning extents with -o discard"); 2) To track block groups for automatic reclaim, introduced more recently by commit 18bb8bbf13c1 ("btrfs: zoned: automatically reclaim zones") So document those two other use cases. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-04-17btrfs: scrub: remove the old scrub recheck codeQu Wenruo1-11/+0
The old scrub code has different entrance to verify the content, and since we have removed the writeback path, now we can start removing the re-check part, including: - scrub_recover structure - scrub_sector::recover member - function scrub_setup_recheck_block() - function scrub_recheck_block() - function scrub_recheck_block_checksum() - function scrub_repair_block_group_good_copy() - function scrub_repair_sector_from_good_copy() - function scrub_is_page_on_raid56() - function full_stripe_lock() - function search_full_stripe_lock() - function get_full_stripe_logical() - function insert_full_stripe_lock() - function lock_full_stripe() - function unlock_full_stripe() - btrfs_block_group::full_stripe_locks_root member - btrfs_full_stripe_locks_tree structure This infrastructure is to ensure RAID56 scrub is properly handling recovery and P/Q scrub correctly. This is no longer needed, before P/Q scrub we will wait for all the involved data stripes to be scrubbed first, and RAID56 code has internal lock to ensure no race in the same full stripe. - function scrub_print_warning() - function scrub_get_recover() - function scrub_put_recover() - function scrub_handle_errored_block() - function scrub_setup_recheck_block() - function scrub_bio_wait_endio() - function scrub_submit_raid56_bio_wait() - function scrub_recheck_block_on_raid56() - function scrub_recheck_block() - function scrub_recheck_block_checksum() - function scrub_repair_block_from_good_copy() - function scrub_repair_sector_from_good_copy() And two more functions exported temporarily for later cleanup: - alloc_scrub_sector() - alloc_scrub_block() Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-04-17btrfs: remove bytes_used argument from btrfs_make_block_group()Filipe Manana1-1/+1
The only caller of btrfs_make_block_group() always passes 0 as the value for the bytes_used argument, so remove it. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-02-15btrfs: remove the bdev argument to btrfs_rmap_blockChristoph Hellwig1-2/+1
The only user in the zoned remap code is gone now, so remove the argument. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2023-02-13btrfs: don't use size classes for zoned file systemsBoris Burkov1-0/+1
When a file system has ZNS devices which are constrained by a maximum number of active block groups, then not being able to use all the block groups for every allocation is not ideal, and could cause us to loop a ton with mixed size allocations. In general, since zoned doesn't write into gaps behind where block groups are writing, it is not susceptible to the same sort of fragmentation that size classes are designed to solve, so we can skip size classes for zoned file systems in general, even though there would probably be no harm for SMR devices. Signed-off-by: Boris Burkov <boris@bur.io> Signed-off-by: David Sterba <dsterba@suse.com>
2023-02-13btrfs: introduce size class to block group allocatorBoris Burkov1-1/+19
The aim of this patch is to reduce the fragmentation of block groups under certain unhappy workloads. It is particularly effective when the size of extents correlates with their lifetime, which is something we have observed causing fragmentation in the fleet at Meta. This patch categorizes extents into size classes: - x < 128KiB: "small" - 128KiB < x < 8MiB: "medium" - x > 8MiB: "large" and as much as possible reduces allocations of extents into block groups that don't match the size class. This takes advantage of any (possible) correlation between size and lifetime and also leaves behind predictable re-usable gaps when extents are freed; small writes don't gum up bigger holes. Size classes are implemented in the following way: - Mark each new block group with a size class of the first allocation that goes into it. - Add two new passes to ffe: "unset size class" and "wrong size class". First, try only matching block groups, then try unset ones, then allow allocation of new ones, and finally allow mismatched block groups. - Filtering is done just by skipping inappropriate ones, there is no special size class indexing. Other solutions I considered were: - A best fit allocator with an rb-tree. This worked well, as small writes didn't leak big holes from large freed extents, but led to regressions in ffe and write performance due to lock contention on the rb-tree with every allocation possibly updating it in parallel. Perhaps something clever could be done to do the updates in the background while being "right enough". - A fixed size "working set". This prevents freeing an extent drastically changing where writes currently land, and seems like a good option too. Doesn't take advantage of size in any way. - The same size class idea, but implemented with xarray marks. This turned out to be slower than looping the linked list and skipping wrong block groups, and is also less flexible since we must have only 3 size classes (max #marks). With the current approach we can have as many as we like. Performance testing was done via: https://github.com/josefbacik/fsperf Of particular relevance are the new fragmentation specific tests. A brief summary of the testing results: - Neutral results on existing tests. There are some minor regressions and improvements here and there, but nothing that truly stands out as notable. - Improvement on new tests where size class and extent lifetime are correlated. Fragmentation in these cases is completely eliminated and write performance is generally a little better. There is also significant improvement where extent sizes are just a bit larger than the size class boundaries. - Regression on one new tests: where the allocations are sized intentionally a hair under the borders of the size classes. Results are neutral on the test that intentionally attacks this new scheme by mixing extent size and lifetime. The full dump of the performance results can be found here: https://bur.io/fsperf/size-class-2022-11-15.txt (there are ANSI escape codes, so best to curl and view in terminal) Here is a snippet from the full results for a new test which mixes buffered writes appending to a long lived set of files and large short lived fallocates: bufferedappendvsfallocate results metric baseline current stdev diff ====================================================================================== avg_commit_ms 31.13 29.20 2.67 -6.22% bg_count 14 15.60 0 11.43% commits 11.10 12.20 0.32 9.91% elapsed 27.30 26.40 2.98 -3.30% end_state_mount_ns 11122551.90 10635118.90 851143.04 -4.38% end_state_umount_ns 1.36e+09 1.35e+09 12248056.65 -1.07% find_free_extent_calls 116244.30 114354.30 964.56 -1.63% find_free_extent_ns_max 599507.20 1047168.20 103337.08 74.67% find_free_extent_ns_mean 3607.19 3672.11 101.20 1.80% find_free_extent_ns_min 500 512 6.67 2.40% find_free_extent_ns_p50 2848 2876 37.65 0.98% find_free_extent_ns_p95 4916 5000 75.45 1.71% find_free_extent_ns_p99 20734.49 20920.48 1670.93 0.90% frag_pct_max 61.67 0 8.05 -100.00% frag_pct_mean 43.59 0 6.10 -100.00% frag_pct_min 25.91 0 16.60 -100.00% frag_pct_p50 42.53 0 7.25 -100.00% frag_pct_p95 61.67 0 8.05 -100.00% frag_pct_p99 61.67 0 8.05 -100.00% fragmented_bg_count 6.10 0 1.45 -100.00% max_commit_ms 49.80 46 5.37 -7.63% sys_cpu 2.59 2.62 0.29 1.39% write_bw_bytes 1.62e+08 1.68e+08 17975843.50 3.23% write_clat_ns_mean 57426.39 54475.95 2292.72 -5.14% write_clat_ns_p50 46950.40 42905.60 2101.35 -8.62% write_clat_ns_p99 148070.40 143769.60 2115.17 -2.90% write_io_kbytes 4194304 4194304 0 0.00% write_iops 2476.15 2556.10 274.29 3.23% write_lat_ns_max 2101667.60 2251129.50 370556.59 7.11% write_lat_ns_mean 59374.91 55682.00 2523.09 -6.22% write_lat_ns_min 17353.10 16250 1646.08 -6.36% There are some mixed improvements/regressions in most metrics along with an elimination of fragmentation in this workload. On the balance, the drastic 1->0 improvement in the happy cases seems worth the mix of regressions and improvements we do observe. Some considerations for future work: - Experimenting with more size classes - More hinting/search ordering work to approximate a best-fit allocator Signed-off-by: Boris Burkov <boris@bur.io> Signed-off-by: David Sterba <dsterba@suse.com>
2022-12-05btrfs: convert btrfs_block_group::seq_zone to runtime flagDavid Sterba1-3/+2
In zoned mode the sequential status of zone can be also tracked in the runtime flags of block group. Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-12-05btrfs: convert btrfs_block_group::needs_free_space to runtime flagDavid Sterba1-6/+2
We already have flags in block group to track various status bits, convert needs_free_space as well and reduce size of btrfs_block_group. Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-12-05btrfs: skip update of block group item if used bytes are the sameQu Wenruo1-0/+6
[BACKGROUND] When committing a transaction, we will update block group items for all dirty block groups. But in fact, dirty block groups don't always need to update their block group items. It's pretty common to have a metadata block group which experienced several COW operations, but still have the same amount of used bytes. In that case, we may unnecessarily COW a tree block doing nothing. [ENHANCEMENT] This patch will introduce btrfs_block_group::commit_used member to remember the last used bytes, and use that new member to skip unnecessary block group item update. This would be more common for large filesystems, where metadata block group can be as large as 1GiB, containing at most 64K metadata items. In that case, if COW added and then deleted one metadata item near the end of the block group, then it's completely possible we don't need to touch the block group item at all. [BENCHMARK] The change itself can have quite a high chance (20~80%) to skip block group item updates in lot of workloads. As a result, it would result shorter time spent on btrfs_write_dirty_block_groups(), and overall reduce the execution time of the critical section of btrfs_commit_transaction(). Here comes a fio command, which will do random writes in 4K block size, causing a very heavy metadata updates. fio --filename=$mnt/file --size=512M --rw=randwrite --direct=1 --bs=4k \ --ioengine=libaio --iodepth=64 --runtime=300 --numjobs=4 \ --name=random_write --fallocate=none --time_based --fsync_on_close=1 The file size (512M) and number of threads (4) means 2GiB file size in total, but during the full 300s run time, my dedicated SATA SSD is able to write around 20~25GiB, which is over 10 times the file size. Thus after we fill the initial 2G, we should not cause much block group item updates. Please note, the fio numbers by themselves don't have much change, but if we look deeper, there is some reduced execution time, especially for the critical section of btrfs_commit_transaction(). I added extra trace_printk() to measure the following per-transaction execution time: - Critical section of btrfs_commit_transaction() By re-using the existing update_commit_stats() function, which has already calculated the interval correctly. - The while() loop for btrfs_write_dirty_block_groups() Although this includes the execution time of btrfs_run_delayed_refs(), it should still be representative overall. Both result involves transid 7~30, the same amount of transaction committed. The result looks like this: | Before | After | Diff ----------------------+-------------------+----------------+-------- Transaction interval | 229247198.5 | 215016933.6 | -6.2% Block group interval | 23133.33333 | 18970.83333 | -18.0% The change in block group item updates is more obvious, as skipped block group item updates also mean less delayed refs. And the overall execution time for that block group update loop is pretty small, thus we can assume the extent tree is already mostly cached. If we can skip an uncached tree block, it would cause more obvious change. Unfortunately the overall reduction in commit transaction critical section is much smaller, as the block group item updates loop is not really the major part, at least not for the above fio script. But still we have a observable reduction in the critical section. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-12-05btrfs: move btrfs_should_fragment_free_space into block-group.cJosef Bacik1-10/+1
This function uses functions that are not defined in block-group.h, move it into block-group.c in order to keep the header clean. Reviewed-by: Qu Wenruo <wqu@suse.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-09-26btrfs: move btrfs_full_stripe_locks_tree into block-group.hJosef Bacik1-0/+8
This is actually embedded in struct btrfs_block_group, so move this definition to block-group.h, and then open-code the init of the tree where we init the rest of the block group instead of using a helper. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-09-26btrfs: move btrfs_caching_type to block-group.hJosef Bacik1-0/+7
This is a block group related definition, move it into block-group.h. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-09-26btrfs: get rid of block group caching progress logicOmar Sandoval1-2/+0
struct btrfs_caching_ctl::progress and struct btrfs_block_group::last_byte_to_unpin were previously needed to ensure that unpin_extent_range() didn't return a range to the free space cache before the caching thread had a chance to cache that range. However, the commit "btrfs: fix space cache corruption and potential double allocations" made it so that we always synchronously cache the block group at the time that we pin the extent, so this machinery is no longer necessary. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-09-26btrfs: delete btrfs_wait_space_cache_v1_finishedJosef Bacik1-2/+0
We used to use this in a few spots, but now we only use it directly inside of block-group.c, so remove the helper and just open code where we were using it. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-09-26btrfs: remove BLOCK_GROUP_FLAG_HAS_CACHING_CTLJosef Bacik1-1/+0
This is used mostly to determine if we need to look at the caching ctl list and clean up any references to this block group. However we never clear this flag, specifically because we need to know if we have to remove a caching ctl we have for this block group still. This is in the remove block group path which isn't a fast path, so the optimization doesn't really matter, simplify this logic and remove the flag. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-09-26btrfs: convert block group bit field to use bit helpersJosef Bacik1-8/+13
We use a bit field in the btrfs_block_group for different flags, however this is awkward because we have to hold the block_group->lock for any modification of any of these fields, and makes the code clunky for a few of these flags. Convert these to a properly flags setup so we can utilize the bit helpers. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-08-23btrfs: fix space cache corruption and potential double allocationsOmar Sandoval1-3/+1
When testing space_cache v2 on a large set of machines, we encountered a few symptoms: 1. "unable to add free space :-17" (EEXIST) errors. 2. Missing free space info items, sometimes caught with a "missing free space info for X" error. 3. Double-accounted space: ranges that were allocated in the extent tree and also marked as free in the free space tree, ranges that were marked as allocated twice in the extent tree, or ranges that were marked as free twice in the free space tree. If the latter made it onto disk, the next reboot would hit the BUG_ON() in add_new_free_space(). 4. On some hosts with no on-disk corruption or error messages, the in-memory space cache (dumped with drgn) disagreed with the free space tree. All of these symptoms have the same underlying cause: a race between caching the free space for a block group and returning free space to the in-memory space cache for pinned extents causes us to double-add a free range to the space cache. This race exists when free space is cached from the free space tree (space_cache=v2) or the extent tree (nospace_cache, or space_cache=v1 if the cache needs to be regenerated). struct btrfs_block_group::last_byte_to_unpin and struct btrfs_block_group::progress are supposed to protect against this race, but commit d0c2f4fa555e ("btrfs: make concurrent fsyncs wait less when waiting for a transaction commit") subtly broke this by allowing multiple transactions to be unpinning extents at the same time. Specifically, the race is as follows: 1. An extent is deleted from an uncached block group in transaction A. 2. btrfs_commit_transaction() is called for transaction A. 3. btrfs_run_delayed_refs() -> __btrfs_free_extent() runs the delayed ref for the deleted extent. 4. __btrfs_free_extent() -> do_free_extent_accounting() -> add_to_free_space_tree() adds the deleted extent back to the free space tree. 5. do_free_extent_accounting() -> btrfs_update_block_group() -> btrfs_cache_block_group() queues up the block group to get cached. block_group->progress is set to block_group->start. 6. btrfs_commit_transaction() for transaction A calls switch_commit_roots(). It sets block_group->last_byte_to_unpin to block_group->progress, which is block_group->start because the block group hasn't been cached yet. 7. The caching thread gets to our block group. Since the commit roots were already switched, load_free_space_tree() sees the deleted extent as free and adds it to the space cache. It finishes caching and sets block_group->progress to U64_MAX. 8. btrfs_commit_transaction() advances transaction A to TRANS_STATE_SUPER_COMMITTED. 9. fsync calls btrfs_commit_transaction() for transaction B. Since transaction A is already in TRANS_STATE_SUPER_COMMITTED and the commit is for fsync, it advances. 10. btrfs_commit_transaction() for transaction B calls switch_commit_roots(). This time, the block group has already been cached, so it sets block_group->last_byte_to_unpin to U64_MAX. 11. btrfs_commit_transaction() for transaction A calls btrfs_finish_extent_commit(), which calls unpin_extent_range() for the deleted extent. It sees last_byte_to_unpin set to U64_MAX (by transaction B!), so it adds the deleted extent to the space cache again! This explains all of our symptoms above: * If the sequence of events is exactly as described above, when the free space is re-added in step 11, it will fail with EEXIST. * If another thread reallocates the deleted extent in between steps 7 and 11, then step 11 will silently re-add that space to the space cache as free even though it is actually allocated. Then, if that space is allocated *again*, the free space tree will be corrupted (namely, the wrong item will be deleted). * If we don't catch this free space tree corruption, it will continue to get worse as extents are deleted and reallocated. The v1 space_cache is synchronously loaded when an extent is deleted (btrfs_update_block_group() with alloc=0 calls btrfs_cache_block_group() with load_cache_only=1), so it is not normally affected by this bug. However, as noted above, if we fail to load the space cache, we will fall back to caching from the extent tree and may hit this bug. The easiest fix for this race is to also make caching from the free space tree or extent tree synchronous. Josef tested this and found no performance regressions. A few extra changes fall out of this change. Namely, this fix does the following, with step 2 being the crucial fix: 1. Factor btrfs_caching_ctl_wait_done() out of btrfs_wait_block_group_cache_done() to allow waiting on a caching_ctl that we already hold a reference to. 2. Change the call in btrfs_cache_block_group() of btrfs_wait_space_cache_v1_finished() to btrfs_caching_ctl_wait_done(), which makes us wait regardless of the space_cache option. 3. Delete the now unused btrfs_wait_space_cache_v1_finished() and space_cache_v1_done(). 4. Change btrfs_cache_block_group()'s `int load_cache_only` parameter to `bool wait` to more accurately describe its new meaning. 5. Change a few callers which had a separate call to btrfs_wait_block_group_cache_done() to use wait = true instead. 6. Make btrfs_wait_block_group_cache_done() static now that it's not used outside of block-group.c anymore. Fixes: d0c2f4fa555e ("btrfs: make concurrent fsyncs wait less when waiting for a transaction commit") CC: stable@vger.kernel.org # 5.12+ Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-06-21btrfs: zoned: prevent allocation from previous data relocation BGNaohiro Aota1-0/+1
After commit 5f0addf7b890 ("btrfs: zoned: use dedicated lock for data relocation"), we observe IO errors on e.g, btrfs/232 like below. [09.0][T4038707] WARNING: CPU: 3 PID: 4038707 at fs/btrfs/extent-tree.c:2381 btrfs_cross_ref_exist+0xfc/0x120 [btrfs] <snip> [09.9][T4038707] Call Trace: [09.5][T4038707] <TASK> [09.3][T4038707] run_delalloc_nocow+0x7f1/0x11a0 [btrfs] [09.6][T4038707] ? test_range_bit+0x174/0x320 [btrfs] [09.2][T4038707] ? fallback_to_cow+0x980/0x980 [btrfs] [09.3][T4038707] ? find_lock_delalloc_range+0x33e/0x3e0 [btrfs] [09.5][T4038707] btrfs_run_delalloc_range+0x445/0x1320 [btrfs] [09.2][T4038707] ? test_range_bit+0x320/0x320 [btrfs] [09.4][T4038707] ? lock_downgrade+0x6a0/0x6a0 [09.2][T4038707] ? orc_find.part.0+0x1ed/0x300 [09.5][T4038707] ? __module_address.part.0+0x25/0x300 [09.0][T4038707] writepage_delalloc+0x159/0x310 [btrfs] <snip> [09.4][ C3] sd 10:0:1:0: [sde] tag#2620 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s [09.5][ C3] sd 10:0:1:0: [sde] tag#2620 Sense Key : Illegal Request [current] [09.9][ C3] sd 10:0:1:0: [sde] tag#2620 Add. Sense: Unaligned write command [09.5][ C3] sd 10:0:1:0: [sde] tag#2620 CDB: Write(16) 8a 00 00 00 00 00 02 f3 63 87 00 00 00 2c 00 00 [09.4][ C3] critical target error, dev sde, sector 396041272 op 0x1:(WRITE) flags 0x800 phys_seg 3 prio class 0 [09.9][ C3] BTRFS error (device dm-1): bdev /dev/mapper/dml_102_2 errs: wr 1, rd 0, flush 0, corrupt 0, gen 0 The IO errors occur when we allocate a regular extent in previous data relocation block group. On zoned btrfs, we use a dedicated block group to relocate a data extent. Thus, we allocate relocating data extents (pre-alloc) only from the dedicated block group and vice versa. Once the free space in the dedicated block group gets tight, a relocating extent may not fit into the block group. In that case, we need to switch the dedicated block group to the next one. Then, the previous one is now freed up for allocating a regular extent. The BG is already not enough to allocate the relocating extent, but there is still room to allocate a smaller extent. Now the problem happens. By allocating a regular extent while nocow IOs for the relocation is still on-going, we will issue WRITE IOs (for relocation) and ZONE APPEND IOs (for the regular writes) at the same time. That mixed IOs confuses the write pointer and arises the unaligned write errors. This commit introduces a new bit 'zoned_data_reloc_ongoing' to the btrfs_block_group. We set this bit before releasing the dedicated block group, and no extent are allocated from a block group having this bit set. This bit is similar to setting block_group->ro, but is different from it by allowing nocow writes to start. Once all the nocow IO for relocation is done (hooked from btrfs_finish_ordered_io), we reset the bit to release the block group for further allocation. Fixes: c2707a255623 ("btrfs: zoned: add a dedicated data relocation block group") CC: stable@vger.kernel.org # 5.16+ Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-05-16btrfs: zoned: properly finish block group on metadata writeNaohiro Aota1-0/+2
Commit be1a1d7a5d24 ("btrfs: zoned: finish fully written block group") introduced zone finishing code both for data and metadata end_io path. However, the metadata side is not working as it should. First, it compares logical address (eb->start + eb->len) with offset within a block group (cache->zone_capacity) in submit_eb_page(). That essentially disabled zone finishing on metadata end_io path. Furthermore, fixing the issue above revealed we cannot call btrfs_zone_finish_endio() in end_extent_buffer_writeback(). We cannot call btrfs_lookup_block_group() which require spin lock inside end_io context. Introduce btrfs_schedule_zone_finish_bg() to wait for the extent buffer writeback and do the zone finish IO in a workqueue. Also, drop EXTENT_BUFFER_ZONE_FINISH as it is no longer used. Fixes: be1a1d7a5d24 ("btrfs: zoned: finish fully written block group") CC: stable@vger.kernel.org # 5.16+ Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-05-16btrfs: avoid double search for block group during NOCOW writesFilipe Manana1-2/+3
When doing a NOCOW write, either through direct IO or buffered IO, we do two lookups for the block group that contains the target extent: once when we call btrfs_inc_nocow_writers() and then later again when we call btrfs_dec_nocow_writers() after creating the ordered extent. The lookups require taking a lock and navigating the red black tree used to track all block groups, which can take a non-negligible amount of time for a large filesystem with thousands of block groups, as well as lock contention and cache line bouncing. Improve on this by having a single block group search: making btrfs_inc_nocow_writers() return the block group to its caller and then have the caller pass that block group to btrfs_dec_nocow_writers(). This is part of a patchset comprised of the following patches: btrfs: remove search start argument from first_logical_byte() btrfs: use rbtree with leftmost node cached for tracking lowest block group btrfs: use a read/write lock for protecting the block groups tree btrfs: return block group directly at btrfs_next_block_group() btrfs: avoid double search for block group during NOCOW writes The following test was used to test these changes from a performance perspective: $ cat test.sh #!/bin/bash modprobe null_blk nr_devices=0 NULL_DEV_PATH=/sys/kernel/config/nullb/nullb0 mkdir $NULL_DEV_PATH if [ $? -ne 0 ]; then echo "Failed to create nullb0 directory." exit 1 fi echo 2 > $NULL_DEV_PATH/submit_queues echo 16384 > $NULL_DEV_PATH/size # 16G echo 1 > $NULL_DEV_PATH/memory_backed echo 1 > $NULL_DEV_PATH/power DEV=/dev/nullb0 MNT=/mnt/nullb0 LOOP_MNT="$MNT/loop" MOUNT_OPTIONS="-o ssd -o nodatacow" MKFS_OPTIONS="-R free-space-tree -O no-holes" cat <<EOF > /tmp/fio-job.ini [io_uring_writes] rw=randwrite fsync=0 fallocate=posix group_reporting=1 direct=1 ioengine=io_uring iodepth=64 bs=64k filesize=1g runtime=300 time_based directory=$LOOP_MNT numjobs=8 thread EOF echo performance | \ tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor echo echo "Using config:" echo cat /tmp/fio-job.ini echo umount $MNT &> /dev/null mkfs.btrfs -f $MKFS_OPTIONS $DEV &> /dev/null mount $MOUNT_OPTIONS $DEV $MNT mkdir $LOOP_MNT truncate -s 4T $MNT/loopfile mkfs.btrfs -f $MKFS_OPTIONS $MNT/loopfile &> /dev/null mount $MOUNT_OPTIONS $MNT/loopfile $LOOP_MNT # Trigger the allocation of about 3500 data block groups, without # actually consuming space on underlying filesystem, just to make # the tree of block group large. fallocate -l 3500G $LOOP_MNT/filler fio /tmp/fio-job.ini umount $LOOP_MNT umount $MNT echo 0 > $NULL_DEV_PATH/power rmdir $NULL_DEV_PATH The test was run on a non-debug kernel (Debian's default kernel config), the result were the following. Before patchset: WRITE: bw=1455MiB/s (1526MB/s), 1455MiB/s-1455MiB/s (1526MB/s-1526MB/s), io=426GiB (458GB), run=300006-300006msec After patchset: WRITE: bw=1503MiB/s (1577MB/s), 1503MiB/s-1503MiB/s (1577MB/s-1577MB/s), io=440GiB (473GB), run=300006-300006msec +3.3% write throughput and +3.3% IO done in the same time period. The test has somewhat limited coverage scope, as with only NOCOW writes we get less contention on the red black tree of block groups, since we don't have the extra contention caused by COW writes, namely when allocating data extents, pinning and unpinning data extents, but on the hand there's access to tree in the NOCOW path, when incrementing a block group's number of NOCOW writers. Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-04-06btrfs: zoned: activate block group only for extent allocationNaohiro Aota1-0/+4
In btrfs_make_block_group(), we activate the allocated block group, expecting that the block group is soon used for allocation. However, the chunk allocation from flush_space() context broke the assumption. There can be a large time gap between the chunk allocation time and the extent allocation time from the chunk. Activating the empty block groups pre-allocated from flush_space() context can exhaust the active zone counter of a device. Once we use all the active zone counts for empty pre-allocated block groups, we cannot activate new block group for the other things: metadata, tree-log, or data relocation block group. That failure results in a fake -ENOSPC. This patch introduces CHUNK_ALLOC_FORCE_FOR_EXTENT to distinguish the chunk allocation from find_free_extent(). Now, the new block group is activated only in that context. Fixes: eb66a010d518 ("btrfs: zoned: activate new block group") CC: stable@vger.kernel.org # 5.16+ Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2022-03-14btrfs: add support for multiple global rootsJosef Bacik1-0/+1
With extent tree v2 you will be able to create multiple csum, extent, and free space trees. They will be used based on the block group, which will now use the block_group_item->chunk_objectid to point to the set of global roots that it will use. When allocating new block groups we'll simply mod the gigabyte offset of the block group against the number of global roots we have and that will be the block groups global id. >From there we can take the bytenr that we're modifying in the respective tree, look up the block group and get that block groups corresponding global root id. From there we can get to the appropriate global root for that bytenr. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-10-26btrfs: fix deadlock between chunk allocation and chunk btree modificationsFilipe Manana1-0/+2
When a task is doing some modification to the chunk btree and it is not in the context of a chunk allocation or a chunk removal, it can deadlock with another task that is currently allocating a new data or metadata chunk. These contexts are the following: * When relocating a system chunk, when we need to COW the extent buffers that belong to the chunk btree; * When adding a new device (ioctl), where we need to add a new device item to the chunk btree; * When removing a device (ioctl), where we need to remove a device item from the chunk btree; * When resizing a device (ioctl), where we need to update a device item in the chunk btree and may need to relocate a system chunk that lies beyond the new device size when shrinking a device. The problem happens due to a sequence of steps like the following: 1) Task A starts a data or metadata chunk allocation and it locks the chunk mutex; 2) Task B is relocating a system chunk, and when it needs to COW an extent buffer of the chunk btree, it has locked both that extent buffer as well as its parent extent buffer; 3) Since there is not enough available system space, either because none of the existing system block groups have enough free space or because the only one with enough free space is in RO mode due to the relocation, task B triggers a new system chunk allocation. It blocks when trying to acquire the chunk mutex, currently held by task A; 4) Task A enters btrfs_chunk_alloc_add_chunk_item(), in order to insert the new chunk item into the chunk btree and update the existing device items there. But in order to do that, it has to lock the extent buffer that task B locked at step 2, or its parent extent buffer, but task B is waiting on the chunk mutex, which is currently locked by task A, therefore resulting in a deadlock. One example report when the deadlock happens with system chunk relocation: INFO: task kworker/u9:5:546 blocked for more than 143 seconds. Not tainted 5.15.0-rc3+ #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u9:5 state:D stack:25936 pid: 546 ppid: 2 flags:0x00004000 Workqueue: events_unbound btrfs_async_reclaim_metadata_space Call Trace: context_switch kernel/sched/core.c:4940 [inline] __schedule+0xcd9/0x2530 kernel/sched/core.c:6287 schedule+0xd3/0x270 kernel/sched/core.c:6366 rwsem_down_read_slowpath+0x4ee/0x9d0 kernel/locking/rwsem.c:993 __down_read_common kernel/locking/rwsem.c:1214 [inline] __down_read kernel/locking/rwsem.c:1223 [inline] down_read_nested+0xe6/0x440 kernel/locking/rwsem.c:1590 __btrfs_tree_read_lock+0x31/0x350 fs/btrfs/locking.c:47 btrfs_tree_read_lock fs/btrfs/locking.c:54 [inline] btrfs_read_lock_root_node+0x8a/0x320 fs/btrfs/locking.c:191 btrfs_search_slot_get_root fs/btrfs/ctree.c:1623 [inline] btrfs_search_slot+0x13b4/0x2140 fs/btrfs/ctree.c:1728 btrfs_update_device+0x11f/0x500 fs/btrfs/volumes.c:2794 btrfs_chunk_alloc_add_chunk_item+0x34d/0xea0 fs/btrfs/volumes.c:5504 do_chunk_alloc fs/btrfs/block-group.c:3408 [inline] btrfs_chunk_alloc+0x84d/0xf50 fs/btrfs/block-group.c:3653 flush_space+0x54e/0xd80 fs/btrfs/space-info.c:670 btrfs_async_reclaim_metadata_space+0x396/0xa90 fs/btrfs/space-info.c:953 process_one_work+0x9df/0x16d0 kernel/workqueue.c:2297 worker_thread+0x90/0xed0 kernel/workqueue.c:2444 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 INFO: task syz-executor:9107 blocked for more than 143 seconds. Not tainted 5.15.0-rc3+ #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor state:D stack:23200 pid: 9107 ppid: 7792 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:4940 [inline] __schedule+0xcd9/0x2530 kernel/sched/core.c:6287 schedule+0xd3/0x270 kernel/sched/core.c:6366 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6425 __mutex_lock_common kernel/locking/mutex.c:669 [inline] __mutex_lock+0xc96/0x1680 kernel/locking/mutex.c:729 btrfs_chunk_alloc+0x31a/0xf50 fs/btrfs/block-group.c:3631 find_free_extent_update_loop fs/btrfs/extent-tree.c:3986 [inline] find_free_extent+0x25cb/0x3a30 fs/btrfs/extent-tree.c:4335 btrfs_reserve_extent+0x1f1/0x500 fs/btrfs/extent-tree.c:4415 btrfs_alloc_tree_block+0x203/0x1120 fs/btrfs/extent-tree.c:4813 __btrfs_cow_block+0x412/0x1620 fs/btrfs/ctree.c:415 btrfs_cow_block+0x2f6/0x8c0 fs/btrfs/ctree.c:570 btrfs_search_slot+0x1094/0x2140 fs/btrfs/ctree.c:1768 relocate_tree_block fs/btrfs/relocation.c:2694 [inline] relocate_tree_blocks+0xf73/0x1770 fs/btrfs/relocation.c:2757 relocate_block_group+0x47e/0xc70 fs/btrfs/relocation.c:3673 btrfs_relocate_block_group+0x48a/0xc60 fs/btrfs/relocation.c:4070 btrfs_relocate_chunk+0x96/0x280 fs/btrfs/volumes.c:3181 __btrfs_balance fs/btrfs/volumes.c:3911 [inline] btrfs_balance+0x1f03/0x3cd0 fs/btrfs/volumes.c:4301 btrfs_ioctl_balance+0x61e/0x800 fs/btrfs/ioctl.c:4137 btrfs_ioctl+0x39ea/0x7b70 fs/btrfs/ioctl.c:4949 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae So fix this by making sure that whenever we try to modify the chunk btree and we are neither in a chunk allocation context nor in a chunk remove context, we reserve system space before modifying the chunk btree. Reported-by: Hao Sun <sunhao.th@gmail.com> Link: https://lore.kernel.org/linux-btrfs/CACkBjsax51i4mu6C0C3vJqQN3NR_iVuucoeG3U1HXjrgzn5FFQ@mail.gmail.com/ Fixes: 79bd37120b1495 ("btrfs: rework chunk allocation to avoid exhaustion of the system chunk array") CC: stable@vger.kernel.org # 5.14+ Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-10-26btrfs: reduce btrfs_update_block_group alloc argument to boolAnand Jain1-1/+1
btrfs_update_block_group() accounts for the number of bytes allocated or freed. Argument @alloc specifies whether the call is for alloc or free. Convert the argument @alloc type from int to bool. Reviewed-by: Su Yue <l@damenly.su> Signed-off-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-10-26btrfs: zoned: implement active zone trackingNaohiro Aota1-0/+2
Add zone_is_active flag to btrfs_block_group. This flag indicates the underlying zones are all active. Such zone active block groups are tracked by fs_info->active_bg_list. btrfs_dev_{set,clear}_active_zone() take responsibility for the underlying device part. They set/clear the bitmap to indicate zone activeness and count the number of zones we can activate left. btrfs_zone_{activate,finish}() take responsibility for the logical part and the list management. In addition, btrfs_zone_finish() wait for any writes on it and send REQ_OP_ZONE_FINISH to the zone. Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-10-26btrfs: zoned: introduce physical_map to btrfs_block_groupNaohiro Aota1-0/+1
We will use a block group's physical location to track active zones and finish fully written zones in the following commits. Since the zone activation is done in the extent allocation context which already holding the tree locks, we can't query the chunk tree for the physical locations. So, copy the location info into a block group and use it for activation. Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-10-26btrfs: zoned: load zone capacity information from devicesNaohiro Aota1-0/+1
The ZNS specification introduces the concept of a Zone Capacity. A zone capacity is an additional per-zone attribute that indicates the number of usable logical blocks within each zone, starting from the first logical block of each zone. It is always smaller or equal to the zone size. With the SINGLE profile, we can set a block group's "capacity" as the same as the underlying zone's Zone Capacity. We will limit the allocation not to exceed in a following commit. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-07-07btrfs: rework chunk allocation to avoid exhaustion of the system chunk arrayFilipe Manana1-2/+4
Commit eafa4fd0ad0607 ("btrfs: fix exhaustion of the system chunk array due to concurrent allocations") fixed a problem that resulted in exhausting the system chunk array in the superblock when there are many tasks allocating chunks in parallel. Basically too many tasks enter the first phase of chunk allocation without previous tasks having finished their second phase of allocation, resulting in too many system chunks being allocated. That was originally observed when running the fallocate tests of stress-ng on a PowerPC machine, using a node size of 64K. However that commit also introduced a deadlock where a task in phase 1 of the chunk allocation waited for another task that had allocated a system chunk to finish its phase 2, but that other task was waiting on an extent buffer lock held by the first task, therefore resulting in both tasks not making any progress. That change was later reverted by a patch with the subject "btrfs: fix deadlock with concurrent chunk allocations involving system chunks", since there is no simple and short solution to address it and the deadlock is relatively easy to trigger on zoned filesystems, while the system chunk array exhaustion is not so common. This change reworks the chunk allocation to avoid the system chunk array exhaustion. It accomplishes that by making the first phase of chunk allocation do the updates of the device items in the chunk btree and the insertion of the new chunk item in the chunk btree. This is done while under the protection of the chunk mutex (fs_info->chunk_mutex), in the same critical section that checks for available system space, allocates a new system chunk if needed and reserves system chunk space. This way we do not have chunk space reserved until the second phase completes. The same logic is applied to chunk removal as well, since it keeps reserved system space long after it is done updating the chunk btree. For direct allocation of system chunks, the previous behaviour remains, because otherwise we would deadlock on extent buffers of the chunk btree. Changes to the chunk btree are by large done by chunk allocation and chunk removal, which first reserve chunk system space and then later do changes to the chunk btree. The other remaining cases are uncommon and correspond to adding a device, removing a device and resizing a device. All these other cases do not pre-reserve system space, they modify the chunk btree right away, so they don't hold reserved space for a long period like chunk allocation and chunk removal do. The diff of this change is huge, but more than half of it is just addition of comments describing both how things work regarding chunk allocation and removal, including both the new behavior and the parts of the old behavior that did not change. CC: stable@vger.kernel.org # 5.12+ Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com> Tested-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Tested-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-04-20btrfs: zoned: automatically reclaim zonesJohannes Thumshirn1-0/+3
When a file gets deleted on a zoned file system, the space freed is not returned back into the block group's free space, but is migrated to zone_unusable. As this zone_unusable space is behind the current write pointer it is not possible to use it for new allocations. In the current implementation a zone is reset once all of the block group's space is accounted as zone unusable. This behaviour can lead to premature ENOSPC errors on a busy file system. Instead of only reclaiming the zone once it is completely unusable, kick off a reclaim job once the amount of unusable bytes exceeds a user configurable threshold between 51% and 100%. It can be set per mounted filesystem via the sysfs tunable bg_reclaim_threshold which is set to 75% by default. Similar to reclaiming unused block groups, these dirty block groups are added to a to_reclaim list and then on a transaction commit, the reclaim process is triggered but after we deleted unused block groups, which will free space for the relocation process. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-22btrfs: fix race between writes to swap files and scrubFilipe Manana1-0/+9
When we active a swap file, at btrfs_swap_activate(), we acquire the exclusive operation lock to prevent the physical location of the swap file extents to be changed by operations such as balance and device replace/resize/remove. We also call there can_nocow_extent() which, among other things, checks if the block group of a swap file extent is currently RO, and if it is we can not use the extent, since a write into it would result in COWing the extent. However we have no protection against a scrub operation running after we activate the swap file, which can result in the swap file extents to be COWed while the scrub is running and operating on the respective block group, because scrub turns a block group into RO before it processes it and then back again to RW mode after processing it. That means an attempt to write into a swap file extent while scrub is processing the respective block group, will result in COWing the extent, changing its physical location on disk. Fix this by making sure that block groups that have extents that are used by active swap files can not be turned into RO mode, therefore making it not possible for a scrub to turn them into RO mode. When a scrub finds a block group that can not be turned to RO due to the existence of extents used by swap files, it proceeds to the next block group and logs a warning message that mentions the block group was skipped due to active swap files - this is the same approach we currently use for balance. Fixes: ed46ff3d42378 ("Btrfs: support swap files") CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09btrfs: zoned: relocate block group to repair IO failure in zoned filesystemsNaohiro Aota1-0/+1
When a bad checksum is found and if the filesystem has a mirror of the damaged data, we read the correct data from the mirror and writes it to damaged blocks. This however, violates the sequential write constraints of a zoned block device. We can consider three methods to repair an IO failure in zoned filesystems: (1) Reset and rewrite the damaged zone (2) Allocate new device extent and replace the damaged device extent to the new extent (3) Relocate the corresponding block group Method (1) is most similar to a behavior done with regular devices. However, it also wipes non-damaged data in the same device extent, and so it unnecessary degrades non-damaged data. Method (2) is much like device replacing but done in the same device. It is safe because it keeps the device extent until the replacing finish. However, extending device replacing is non-trivial. It assumes "src_dev->physical == dst_dev->physical". Also, the extent mapping replacing function should be extended to support replacing device extent position in one device. Method (3) invokes relocation of the damaged block group and is straightforward to implement. It relocates all the mirrored device extents, so it potentially is a more costly operation than method (1) or (2). But it relocates only used extents which reduce the total IO size. Let's apply method (3) for now. In the future, we can extend device-replace and apply method (2). For protecting a block group gets relocated multiple time with multiple IO errors, this commit introduces "relocating_repair" bit to show it's now relocating to repair IO failures. Also it uses a new kthread "btrfs-relocating-repair", not to block IO path with relocating process. This commit also supports repairing in the scrub process. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09btrfs: zoned: mark block groups to copy for device-replaceNaohiro Aota1-0/+1
This is the 1/4 patch to support device-replace on zoned filesystems. We have two types of IOs during the device replace process. One is an IO to "copy" (by the scrub functions) all the device extents from the source device to the destination device. The other one is an IO to "clone" (by handle_ops_on_dev_replace()) new incoming write IOs from users to the source device into the target device. Cloning incoming IOs can break the sequential write rule in on target device. When a write is mapped in the middle of a block group, the IO is directed to the middle of a target device zone, which breaks the sequential write requirement. However, the cloning function cannot be disabled since incoming IOs targeting already copied device extents must be cloned so that the IO is executed on the target device. We cannot use dev_replace->cursor_{left,right} to determine whether a bio is going to a not yet copied region. Since we have a time gap between finishing btrfs_scrub_dev() and rewriting the mapping tree in btrfs_dev_replace_finishing(), we can have a newly allocated device extent which is never cloned nor copied. So the point is to copy only already existing device extents. This patch introduces mark_block_group_to_copy() to mark existing block groups as a target of copying. Then, handle_ops_on_dev_replace() and dev-replace can check the flag to do their job. Also, btrfs_finish_block_group_to_copy() will check if the copied stripe is the last stripe in the block group. With the last stripe copied, the to_copy flag is finally disabled. Afterwards we can safely clone incoming IOs on this block group. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09btrfs: zoned: serialize metadata IONaohiro Aota1-0/+1
We cannot use zone append for writing metadata, because the B-tree nodes have references to each other using logical address. Without knowing the address in advance, we cannot construct the tree in the first place. So we need to serialize write IOs for metadata. We cannot add a mutex around allocation and submission because metadata blocks are allocated in an earlier stage to build up B-trees. Add a zoned_meta_io_lock and hold it during metadata IO submission in btree_write_cache_pages() to serialize IOs. Furthermore, this adds a per-block group metadata IO submission pointer "meta_write_pointer" to ensure sequential writing, which can break when attempting to write back blocks in an unfinished transaction. If the writing out failed because of a hole and the write out is for data integrity (WB_SYNC_ALL), it returns EAGAIN. A caller like fsync() code should handle this properly e.g. by falling back to a full transaction commit. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09btrfs: zoned: cache if block group is on a sequential zoneJohannes Thumshirn1-0/+3
On a zoned filesystem, cache if a block group is on a sequential write only zone. On sequential write only zones, we can use REQ_OP_ZONE_APPEND for writing data, therefore provide btrfs_use_zone_append() to figure out if IO is targeting a sequential write only zone and we can use REQ_OP_ZONE_APPEND for data writing. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09btrfs: extend btrfs_rmap_block for specifying a deviceNaohiro Aota1-5/+3
btrfs_rmap_block currently reverse-maps the physical addresses on all devices to the corresponding logical addresses. Extend the function to match to a specified device. The old functionality of querying all devices is left intact by specifying NULL as target device. A block_device instead of a btrfs_device is passed into btrfs_rmap_block, as this function is intended to reverse-map the result of a bio, which only has a block_device. Also export the function for later use. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09btrfs: zoned: track unusable bytes for zonesNaohiro Aota1-0/+1
In a zoned filesystem a once written then freed region is not usable until the underlying zone has been reset. So we need to distinguish such unusable space from usable free space. Therefore we need to introduce the "zone_unusable" field to the block group structure, and "bytes_zone_unusable" to the space_info structure to track the unusable space. Pinned bytes are always reclaimed to the unusable space. But, when an allocated region is returned before using e.g., the block group becomes read-only between allocation time and reservation time, we can safely return the region to the block group. For the situation, this commit introduces "btrfs_add_free_space_unused". This behaves the same as btrfs_add_free_space() on regular filesystem. On zoned filesystems, it rewinds the allocation offset. Because the read-only bytes tracks free but unusable bytes when the block group is read-only, we need to migrate the zone_unusable bytes to read-only bytes when a block group is marked read-only. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-09btrfs: zoned: load zone's allocation offsetNaohiro Aota1-0/+6
A zoned filesystem must allocate blocks at the zones' write pointer. The device's write pointer position can be mapped to a logical address within a block group. To facilitate this, add an "alloc_offset" to the block-group to track the logical addresses of the write pointer. This logical address is populated in btrfs_load_block_group_zone_info() from the write pointers of corresponding zones. For now, zoned filesystems the single profile. Supporting non-single profile with zone append writing is not trivial. For example, in the DUP profile, we send a zone append writing IO to two zones on a device. The device reply with written LBAs for the IOs. If the offsets of the returned addresses from the beginning of the zone are different, then it results in different logical addresses. We need fine-grained logical to physical mapping to support such separated physical address issue. Since it should require additional metadata type, disable non-single profiles for now. This commit supports the case all the zones in a block group are sequential. The next patch will handle the case having a conventional zone. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08btrfs: load free space cache asynchronouslyJosef Bacik1-0/+2
While documenting the usage of the commit_root_sem, I noticed that we do not actually take the commit_root_sem in the case of the free space cache. This is problematic because we're supposed to hold that sem while we're reading the commit roots, which is what we do for the free space cache. The reason I did it inline when I originally wrote the code was because there's the case of unpinning where we need to make sure that the free space cache is loaded if we're going to use the free space cache. But we can accomplish the same thing by simply waiting for the cache to be loaded. Rework this code to load the free space cache asynchronously. This allows us to greatly cleanup the caching code because now it's all shared by the various caching methods. We also are now in a position to have the commit_root semaphore held while we're loading the free space cache. And finally our modification of ->last_byte_to_unpin is removed because it can be handled in the proper way on commit. Some care must be taken when replaying the log, when we expect that the free space cache will be read entirely before we start excluding space to replay. This could lead to overwriting space during replay. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-07-27btrfs: convert block group refcount to refcount_tJosef Bacik1-2/+1
We have refcount_t now with the associated library to handle refcounts, which gives us extra debugging around reference count mistakes that may be made. For example it'll warn on any transition from 0->1 or 0->-1, which is handy for noticing cases where we've messed up reference counting. Convert the block group ref counting from an atomic_t to refcount_t and use the appropriate helpers. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-05-25btrfs: move the block group freeze/unfreeze helpers into block-group.cFilipe Manana1-0/+3
The helpers btrfs_freeze_block_group() and btrfs_unfreeze_block_group() used to be named btrfs_get_block_group_trimming() and btrfs_put_block_group_trimming() respectively. At the time they were added to free-space-cache.c, by commit e33e17ee1098 ("btrfs: add missing discards when unpinning extents with -o discard") because all the trimming related functions were in free-space-cache.c. Now that the helpers were renamed and are used in scrub context as well, move them to block-group.c, a much more logical location for them. Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-05-25btrfs: rename member 'trimming' of block group to a more generic nameFilipe Manana1-1/+10
Back in 2014, commit 04216820fe83d5 ("Btrfs: fix race between fs trimming and block group remove/allocation"), I added the 'trimming' member to the block group structure. Its purpose was to prevent races between trimming and block group deletion/allocation by pinning the block group in a way that prevents its logical address and device extents from being reused while trimming is in progress for a block group, so that if another task deletes the block group and then another task allocates a new block group that gets the same logical address and device extents while the trimming task is still in progress. After the previous fix for scrub (patch "btrfs: fix a race between scrub and block group removal/allocation"), scrub now also has the same needs that trimming has, so the member name 'trimming' no longer makes sense. Since there is already a 'pinned' member in the block group that refers to space reservations (pinned bytes), rename the member to 'frozen', add a comment on top of it to describe its general purpose and rename the helpers to increment and decrement the counter as well, to match the new member name. The next patch in the series will move the helpers into a more suitable file (from free-space-cache.c to block-group.c). Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-01-23btrfs: Move and unexport btrfs_rmap_blockNikolay Borisov1-0/+5
It's used only during initial block group reading to map physical address of super block to a list of logical ones. Make it private to block-group.c, add proper kernel doc and ensure it's exported only for tests. Signed-off-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-01-20btrfs: only keep track of data extents for async discardDennis Zhou1-0/+11
As mentioned earlier, discarding data can be done either by issuing an explicit discard or implicitly by reusing the LBA. Metadata block_groups see much more frequent reuse due to well it being metadata. So instead of explicitly discarding metadata block_groups, just leave them be and let the latter implicit discarding be done for them. For mixed block_groups, block_groups which contain both metadata and data, we let them be as higher fragmentation is expected. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-01-20btrfs: discard one region at a time in async discardDennis Zhou1-0/+15
The prior two patches added discarding via a background workqueue. This just piggybacked off of the fstrim code to trim the whole block at once. Well inevitably this is worse performance wise and will aggressively overtrim. But it was nice to plumb the other infrastructure to keep the patches easier to review. This adds the real goal of this series which is discarding slowly (ie. a slow long running fstrim). The discarding is split into two phases, extents and then bitmaps. The reason for this is two fold. First, the bitmap regions overlap the extent regions. Second, discarding the extents first will let the newly trimmed bitmaps have the highest chance of coalescing when being readded to the free space cache. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2020-01-20btrfs: add the beginning of async discard, discard workqueueDennis Zhou1-0/+9
When discard is enabled, everytime a pinned extent is released back to the block_group's free space cache, a discard is issued for the extent. This is an overeager approach when it comes to discarding and helping the SSD maintain enough free space to prevent severe garbage collection situations. This adds the beginning of async discard. Instead of issuing a discard prior to returning it to the free space, it is just marked as untrimmed. The block_group is then added to a LRU which then feeds into a workqueue to issue discards at a much slower rate. Full discarding of unused block groups is still done and will be addressed in a future patch of the series. For now, we don't persist the discard state of extents and bitmaps. Therefore, our failure recovery mode will be to consider extents untrimmed. This lets us handle failure and unmounting as one in the same. On a number of Facebook webservers, I collected data every minute accounting the time we spent in btrfs_finish_extent_commit() (col. 1) and in btrfs_commit_transaction() (col. 2). btrfs_finish_extent_commit() is where we discard extents synchronously before returning them to the free space cache. discard=sync: p99 total per minute p99 total per minute Drive | extent_commit() (ms) | commit_trans() (ms) --------------------------------------------------------------- Drive A | 434 | 1170 Drive B | 880 | 2330 Drive C | 2943 | 3920 Drive D | 4763 | 5701 discard=async: p99 total per minute p99 total per minute Drive | extent_commit() (ms) | commit_trans() (ms) -------------------------------------------------------------- Drive A | 134 | 956 Drive B | 64 | 1972 Drive C | 59 | 1032 Drive D | 62 | 1200 While it's not great that the stats are cumulative over 1m, all of these servers are running the same workload and and the delta between the two are substantial. We are spending significantly less time in btrfs_finish_extent_commit() which is responsible for discarding. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennis@kernel.org> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
2019-11-18btrfs: scrub: Don't check free space before marking a block group ROQu Wenruo1-1/+2
[BUG] When running btrfs/072 with only one online CPU, it has a pretty high chance to fail: btrfs/072 12s ... _check_dmesg: something found in dmesg (see xfstests-dev/results//btrfs/072.dmesg) - output mismatch (see xfstests-dev/results//btrfs/072.out.bad) --- tests/btrfs/072.out 2019-10-22 15:18:14.008965340 +0800 +++ /xfstests-dev/results//btrfs/072.out.bad 2019-11-14 15:56:45.877152240 +0800 @@ -1,2 +1,3 @@ QA output created by 072 Silence is golden +Scrub find errors in "-m dup -d single" test ... And with the following call trace: BTRFS info (device dm-5): scrub: started on devid 1 ------------[ cut here ]------------ BTRFS: Transaction aborted (error -27) WARNING: CPU: 0 PID: 55087 at fs/btrfs/block-group.c:1890 btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs] CPU: 0 PID: 55087 Comm: btrfs Tainted: G W O 5.4.0-rc1-custom+ #13 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:btrfs_create_pending_block_groups+0x3e6/0x470 [btrfs] Call Trace: __btrfs_end_transaction+0xdb/0x310 [btrfs] btrfs_end_transaction+0x10/0x20 [btrfs] btrfs_inc_block_group_ro+0x1c9/0x210 [btrfs] scrub_enumerate_chunks+0x264/0x940 [btrfs] btrfs_scrub_dev+0x45c/0x8f0 [btrfs] btrfs_ioctl+0x31a1/0x3fb0 [btrfs] do_vfs_ioctl+0x636/0xaa0 ksys_ioctl+0x67/0x90 __x64_sys_ioctl+0x43/0x50 do_syscall_64+0x79/0xe0 entry_SYSCALL_64_after_hwframe+0x49/0xbe ---[ end trace 166c865cec7688e7 ]--- [CAUSE] The error number -27 is -EFBIG, returned from the following call chain: btrfs_end_transaction() |- __btrfs_end_transaction() |- btrfs_create_pending_block_groups() |- btrfs_finish_chunk_alloc() |- btrfs_add_system_chunk() This happens because we have used up all space of btrfs_super_block::sys_chunk_array. The root cause is, we have the following bad loop of creating tons of system chunks: 1. The only SYSTEM chunk is being scrubbed It's very common to have only one SYSTEM chunk. 2. New SYSTEM bg will be allocated As btrfs_inc_block_group_ro() will check if we have enough space after marking current bg RO. If not, then allocate a new chunk. 3. New SYSTEM bg is still empty, will be reclaimed During the reclaim, we will mark it RO again. 4. That newly allocated empty SYSTEM bg get scrubbed We go back to step 2, as the bg is already mark RO but still not cleaned up yet. If the cleaner kthread doesn't get executed fast enough (e.g. only one CPU), then we will get more and more empty SYSTEM chunks, using up all the space of btrfs_super_block::sys_chunk_array. [FIX] Since scrub/dev-replace doesn't always need to allocate new extent, especially chunk tree extent, so we don't really need to do chunk pre-allocation. To break above spiral, here we introduce a new parameter to btrfs_inc_block_group(), @do_chunk_alloc, which indicates whether we need extra chunk pre-allocation. For relocation, we pass @do_chunk_alloc=true, while for scrub, we pass @do_chunk_alloc=false. This should keep unnecessary empty chunks from popping up for scrub. Also, since there are two parameters for btrfs_inc_block_group_ro(), add more comment for it. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
generated by cgit v1.2.3 (git 2.39.0) at 2024-07-28 11:30:35 +0300