Re: [PATCH] vfs: move ACL cache lookup into generic code

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

On Sat, 23 Jul 2011 05:31:20 +0100, Al Viro <viro@ZenIV.linux.org.uk> wrote:
> On Fri, Jul 22, 2011 at 08:42:35PM -0700, Linus Torvalds wrote:
> > > ... why is that a problem? ?Locking there is mere ->i_lock and getting
> > > a refcount is atomic_inc(). ?Grabbing a reference might be Not Nice from
> > > the cacheline bouncing POV, but...
> > 
> > I agree in theory, but it's not something we've done before. Some of
> > the posix-acl code is pretty disgusting, I didn't even want to go
> > there.
> > 
> > And the case that tends to really *matter* is the "no acls" case
> > anyway, and that's the case that is guaranteed to have no nasty races
> > or odd issues with having to allocate/de-allocate any acl structures.
> > But yes, this could be looked at.
> 
> Heh...  In addition to ocfs2 leak: 9p leaks nicely if v9fs_acl_mode() is
> called with !S_ISDIR(mode).  In that case acl reference is simply lost.
> So yes, it's worth looking at.

something like the below ? I will also audit rest of the code.

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index e98f56d..abad8b3 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -212,7 +212,7 @@ int v9fs_acl_mode(struct inode *dir, mode_t *modep,
 		struct posix_acl *clone;
 
 		if (S_ISDIR(mode))
-			*dpacl = acl;
+			*dpacl = posix_acl_clone(acl, GFP_NOFS);
 		clone = posix_acl_clone(acl, GFP_NOFS);
 		retval = -ENOMEM;
 		if (!clone)
@@ -227,7 +227,7 @@ int v9fs_acl_mode(struct inode *dir, mode_t *modep,
 			*pacl = clone;
 	}
 	*modep  = mode;
-	return 0;
+	retval = 0;
 cleanup:
 	posix_acl_release(acl);
 	return retval;