From e5677f056010298d3a8d43f710f8b445dd73462d Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Tue, 9 Aug 2022 18:36:33 +0200 Subject: btrfs: use atomic_try_cmpxchg in free_extent_buffer Use `atomic_try_cmpxchg(ptr, &old, new)` instead of `atomic_cmpxchg(ptr, old, new) == old` in free_extent_buffer. This has two benefits: - The x86 cmpxchg instruction returns success in the ZF flag, so this change saves a compare after cmpxchg, as well as a related move instruction in the front of cmpxchg. - atomic_try_cmpxchg implicitly assigns the *ptr value to &old when cmpxchg fails, enabling further code simplifications. This patch has no functional change. Reviewed-by: Boris Burkov Signed-off-by: Uros Bizjak Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/extent_io.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'fs/btrfs/extent_io.c') diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index cf4f19e80e2f..63decf3abe26 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -6362,18 +6362,16 @@ static int release_extent_buffer(struct extent_buffer *eb) void free_extent_buffer(struct extent_buffer *eb) { int refs; - int old; if (!eb) return; + refs = atomic_read(&eb->refs); while (1) { - refs = atomic_read(&eb->refs); if ((!test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs <= 3) || (test_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags) && refs == 1)) break; - old = atomic_cmpxchg(&eb->refs, refs, refs - 1); - if (old == refs) + if (atomic_try_cmpxchg(&eb->refs, &refs, refs - 1)) return; } -- cgit