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* [PATCH] btrfs: discard before adding to the free space cache
@ 2019-12-09 19:38 Dennis Zhou
  2019-12-09 20:01 ` Nikolay Borisov
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Dennis Zhou @ 2019-12-09 19:38 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval, Nikolay Borisov
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Returning free space to the free space cache lets it immediately be
reused. So discard before returning the free space otherwise we can race
here.

Fixes: 55e734b728c0 ("btrfs: Don't discard unwritten extents")
Cc: Nikolay Borisov <nborisov@suse.com>
Cc: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/inode.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 625439875299..1ab13943cdf0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3250,13 +3250,14 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 		    clear_reserved_extent &&
 		    !test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
 		    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
-			btrfs_free_reserved_extent(fs_info,
-						   ordered_extent->start,
-						   ordered_extent->disk_len, 1);
 			if (ret && btrfs_test_opt(fs_info, DISCARD))
 				btrfs_discard_extent(fs_info,
 						ordered_extent->start,
 						ordered_extent->disk_len, NULL);
+
+			btrfs_free_reserved_extent(fs_info,
+						   ordered_extent->start,
+						   ordered_extent->disk_len, 1);
 		}
 	}
 
-- 
2.17.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

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Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2019-12-09 19:38 [PATCH] btrfs: discard before adding to the free space cache Dennis Zhou
2019-12-09 20:01 ` Nikolay Borisov
2019-12-11  8:58 ` Johannes Thumshirn
2020-01-02 14:44 ` David Sterba

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