| Message ID | 20221221193540.10078-1-ubizjak@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | posix_acl: Use try_cmpxchg in get_acl | expand |
On Wed, Dec 21, 2022 at 08:35:40PM +0100, Uros Bizjak wrote: > 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: Uros Bizjak <ubizjak@gmail.com> > Cc: Christian Brauner <brauner@kernel.org> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > --- Looks ok to me. But it's not urgent so I'll circle back to this post -rc1. Thanks! Christian
On Fri, Dec 23, 2022 at 11:47:24AM +0100, Christian Brauner wrote: > On Wed, Dec 21, 2022 at 08:35:40PM +0100, Uros Bizjak wrote: > > 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: Uros Bizjak <ubizjak@gmail.com> > > Cc: Christian Brauner <brauner@kernel.org> > > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > > --- > > Looks ok to me. But it's not urgent so I'll circle back to this post > -rc1. Seems good to me. So if there are no objectsions, then applied, thanks! [1/1] posix_acl: Use try_cmpxchg in get_acl commit: 4e1da8fe031303599e78f88e0dad9f44272e4f99
diff --git a/fs/posix_acl.c b/fs/posix_acl.c index d7bc81fc0840..420c689e1bec 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -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; }
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: Uros Bizjak <ubizjak@gmail.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> --- fs/posix_acl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)