Unverified Commit 4e1da8fe authored by Uros Bizjak's avatar Uros Bizjak Committed by Christian Brauner (Microsoft)
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posix_acl: Use try_cmpxchg in get_acl 



Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old
in get_acl. x86 CMPXCHG instruction returns success in ZF flag,
so this change saves a compare after cmpxchg (and related move
instruction in front of cmpxchg).

No functional change intended.

Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarChristian Brauner (Microsoft) <brauner@kernel.org>
parent 1b929c02

fs/posix_acl.c

+1 −1
Original line number Diff line number Diff line
@@ -174,7 +174,7 @@ static struct posix_acl *__get_acl(struct user_namespace *mnt_userns, 
	 * Cache the result, but only if our sentinel is still in place.

	 */

	posix_acl_dup(acl);

	if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))

	if (unlikely(!try_cmpxchg(p, &sentinel, acl)))

		posix_acl_release(acl);

	return acl;

}