[PATCH 1/2] btrfs: reduce the preemptive flushing threshold to 90%

[PATCH 1/2] btrfs: reduce the preemptive flushing threshold to 90%

[Josef Bacik]

The preemptive flushing code was added in order to avoid needing to
synchronously wait for ENOSPC flushing to recover space.  Once we're
almost full however we can essentially flush constantly.  We were using
98% as a threshold to determine if we were simply full, however in
practice this is a really high bar to hit.  For example reports of
systems running into this problem had around 94% usage and thus
continued to flush.  Fix this by lowering the threshold to 90%, which is
a more sane value, especially for smaller file systems.

cc: stable@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=212185
Fixes: 576fa34830af ("btrfs: improve preemptive background space flushing")
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/space-info.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index d9c8d738678f..ddb4878e94df 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -733,7 +733,7 @@ static bool need_preemptive_reclaim(struct btrfs_fs_info *fs_info,
 {
 	u64 global_rsv_size = fs_info->global_block_rsv.reserved;
 	u64 ordered, delalloc;
-	u64 thresh = div_factor_fine(space_info->total_bytes, 98);
+	u64 thresh = div_factor(space_info->total_bytes, 9);
 	u64 used;
 
 	/* If we're just plain full then async reclaim just slows us down. */
-- 
2.26.3