btrfs: fix racy access to discard_ctl data

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Because only one discard worker may be running at any given point, it
could have been safe to modify ->prev_discard, etc. without
synchronization, if not for @override flag in
btrfs_discard_schedule_work() and delayed_work_pending() returning false
while workfn is running.

That may lead to torn reads of u64 for some architectures, but that's
not a big problem as only slightly affects the discard rate.

Suggested-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

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Pavel Begunkov 2020-12-06 15:56:21 +00:00 • committed by David Sterba

parent ea9ed87c73

commit 1ea2872fc6

1 changed files with 3 additions and 7 deletions

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fs/btrfs/discard.c

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