Fix POSIX ACL permission check

After commit 3567866b: "RCUify freeing acls, let check_acl() go ahead in
RCU mode if acl is cached" posix_acl_permission is being called with an
unsupported flag and the permission check fails. This patch fixes the issue.
Signed-off-by: Ari Savolainen <ari.m.savolainen@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -186,7 +186,7 @@ static int check_acl(struct inode *inode, int mask)
 		/* no ->get_acl() calls in RCU mode... */
 		if (acl == ACL_NOT_CACHED)
 			return -ECHILD;
-	        return posix_acl_permission(inode, acl, mask);
+	        return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
 	}
 
 	acl = get_cached_acl(inode, ACL_TYPE_ACCESS);