diff options
| author | Dennis Zhou <dennis@kernel.org> | 2019-12-27 21:12:54 -0800 |
|---|---|---|
| committer | Dennis Zhou <dennis@kernel.org> | 2020-01-02 12:00:48 -0800 |
| commit | f00ffdb40462c1dd9b611ee06cf19b2d495e398b (patch) | |
| tree | d09fbad920f55a663652fe1e2991e0df55d560b1 | |
| parent | fe33c76ede300fd4cb03d0a7878cac0cbee47c42 (diff) | |
| download | misc-async-discard.tar.gz | |
btrfs: add correction to handle -1 edge case in async discardasync-discard
From Dave's testing, it's possible to drive a file system to have -1
discardable_extents and a corresponding negative discardable_bytes. As
btrfs_discard_calc_delay() is the only user of discardable_extents, we
can correct here for any negative discardable_extents/discardable_bytes.
Reported-by: David Sterba <dsterba@suse.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
| -rw-r--r-- | fs/btrfs/discard.c | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c index d5a89e3755ed19..d2c7851e31defb 100644 --- a/fs/btrfs/discard.c +++ b/fs/btrfs/discard.c @@ -518,14 +518,32 @@ void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl) { s32 discardable_extents = atomic_read(&discard_ctl->discardable_extents); + s64 discardable_bytes = atomic64_read(&discard_ctl->discardable_bytes); unsigned iops_limit; unsigned long delay, lower_limit = BTRFS_DISCARD_MIN_DELAY_MSEC; - if (!discardable_extents) - return; - spin_lock(&discard_ctl->lock); + /* + * The following is to fix a potential -1 discrepenancy that I'm not + * sure how to reproduce. But given that this is the only place that + * utilizes these numbers and this is only called by from + * btrfs_finish_extent_commit() which is synchronized, we can correct + * here. + */ + if (discardable_extents < 0) + atomic_add(-discardable_extents, + &discard_ctl->discardable_extents); + + if (discardable_bytes < 0) + atomic64_add(-discardable_bytes, + &discard_ctl->discardable_bytes); + + if (discardable_extents <= 0) { + spin_unlock(&discard_ctl->lock); + return; + } + iops_limit = READ_ONCE(discard_ctl->iops_limit); if (iops_limit) lower_limit = max_t(unsigned long, lower_limit, |