6.16-stable review patch. If anyone has any objections, please let me know.
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From: Filipe Manana fdmanana@suse.com
[ Upstream commit 2697b6159744e5afae0f7715da9f830ba6f9e45a ]
There's this special atomic compare and exchange logic which serves to avoid locking the extent buffers refs_lock spinlock and therefore reduce lock contention, so add a comment to make it more obvious.
Reviewed-by: Boris Burkov boris@bur.io Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Stable-dep-of: ad580dfa388f ("btrfs: fix subpage deadlock in try_release_subpage_extent_buffer()") Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/extent_io.c | 1 + 1 file changed, 1 insertion(+)
--- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3493,6 +3493,7 @@ void free_extent_buffer(struct extent_bu break; }
+ /* Optimization to avoid locking eb->refs_lock. */ if (atomic_try_cmpxchg(&eb->refs, &refs, refs - 1)) return; }