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| author | Uros Bizjak <ubizjak@gmail.com> | 2022-08-09 19:36:33 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2022-09-26 13:27:55 +0300 |
| commit | e5677f056010298d3a8d43f710f8b445dd73462d (patch) | |
| tree | 50fbd1389650c103540c84998d1c3e556d49b44d /fs/btrfs/extent_io.c | |
| parent | fc65bb53180cc13ea646c150316b219d4579ebe3 (diff) | |
| download | linux-e5677f056010298d3a8d43f710f8b445dd73462d.tar.xz | |
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 <boris@bur.io>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/extent_io.c')
| -rw-r--r-- | fs/btrfs/extent_io.c | 6 |
1 files changed, 2 insertions, 4 deletions
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; } |