diff options
| author | Pavel Begunkov <asml.silence@gmail.com> | 2020-12-06 15:56:21 +0000 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2020-12-18 14:59:53 +0100 |
| commit | 1ea2872fc6f2aaee0a4b4f1578b83ffd9f55c6a7 (patch) | |
| tree | 7aed7e743d59c9efb9e1b2430918426b2bedbd28 | |
| parent | ea9ed87c73e87e044b2c58d658eb4ba5216bc488 (diff) | |
btrfs: fix racy access to discard_ctl data
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>
| -rw-r--r-- | fs/btrfs/discard.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c index 36431d7e1334..d641f451f840 100644 --- a/fs/btrfs/discard.c +++ b/fs/btrfs/discard.c @@ -477,13 +477,6 @@ static void btrfs_discard_workfn(struct work_struct *work) discard_ctl->discard_extent_bytes += trimmed; } - /* - * Updated without locks as this is inside the workfn and nothing else - * is reading the values - */ - discard_ctl->prev_discard = trimmed; - discard_ctl->prev_discard_time = ktime_get_ns(); - /* Determine next steps for a block_group */ if (block_group->discard_cursor >= btrfs_block_group_end(block_group)) { if (discard_state == BTRFS_DISCARD_BITMAPS) { @@ -499,7 +492,10 @@ static void btrfs_discard_workfn(struct work_struct *work) } } + now = ktime_get_ns(); spin_lock(&discard_ctl->lock); + discard_ctl->prev_discard = trimmed; + discard_ctl->prev_discard_time = now; discard_ctl->block_group = NULL; spin_unlock(&discard_ctl->lock); |