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

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 535ab6e..94af68b 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -101,7 +101,7 @@
 	struct posix_acl *acl;
 	struct v9fs_session_info *v9ses;
 
-	if (flags & IPERM_FLAG_RCU)
+	if (mask & MAY_NOT_BLOCK)
 		return -ECHILD;
 
 	v9ses = v9fs_inode2v9ses(inode);