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Btrfs: device_replace: fix deadlock for nocow case
commit cb7ab02156
cause a following deadlock found by
xfstests,btrfs/011:
Thread1 is commiting transaction which is blocked at
btrfs_scrub_pause().
Thread2 is calling btrfs_file_aio_write() which has held
inode's @i_mutex and commit transaction(blocked because
Thread1 is committing transaction).
Thread3 is copy_nocow_page worker which will also try to
hold inode @i_mutex, so thread3 will wait Thread1 finished.
Thread4 is waiting pending workers finished which will wait
Thread3 finished. So the problem is like this:
Thread1--->Thread4--->Thread3--->Thread2---->Thread1
Deadlock happens! we fix it by letting Thread1 go firstly,
which means we won't block transaction commit while we are
waiting pending workers finished.
Reported-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
This commit is contained in:
parent
6cf7f77e6b
commit
12cf93728d
1 changed files with 15 additions and 2 deletions
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@ -2686,10 +2686,23 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
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wait_event(sctx->list_wait,
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atomic_read(&sctx->bios_in_flight) == 0);
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atomic_set(&sctx->wr_ctx.flush_all_writes, 0);
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atomic_inc(&fs_info->scrubs_paused);
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wake_up(&fs_info->scrub_pause_wait);
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/*
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* must be called before we decrease @scrub_paused.
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* make sure we don't block transaction commit while
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* we are waiting pending workers finished.
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*/
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wait_event(sctx->list_wait,
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atomic_read(&sctx->workers_pending) == 0);
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scrub_blocked_if_needed(fs_info);
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atomic_set(&sctx->wr_ctx.flush_all_writes, 0);
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mutex_lock(&fs_info->scrub_lock);
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__scrub_blocked_if_needed(fs_info);
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atomic_dec(&fs_info->scrubs_paused);
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mutex_unlock(&fs_info->scrub_lock);
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wake_up(&fs_info->scrub_pause_wait);
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btrfs_put_block_group(cache);
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if (ret)
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