->permission() sanitizing: pass MAY_NOT_BLOCK to ->check_acl()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index f66fc99..a25a4a2 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -199,10 +199,9 @@
 {
 	int error = -EAGAIN;
 
-	if (flags & IPERM_FLAG_RCU) {
+	if (mask & MAY_NOT_BLOCK) {
 		if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
 			error = -ECHILD;
-
 	} else {
 		struct posix_acl *acl;
 		acl = btrfs_get_acl(inode, ACL_TYPE_ACCESS);