Uros Bizjak e5677f0560 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>

2022-09-26 12:27:55 +02:00

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