overlay: permission check with cached acls in tmpfs

tmpfs does not implement ->get_acl method, overlayfs
need to get its cached acls in permission check when
lower or upper fs is tmpfs.

CC: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Xiong Zhou <xzhou@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

common/rc

@@ -1566,6 +1566,15 @@ _require_ext2()
     fi
 }
 
+# this test requires tmpfs filesystem support
+#
+_require_tmpfs()
+{
+	modprobe tmpfs >/dev/null 2>&1
+	grep -q tmpfs /proc/filesystems ||
+		_notrun "this test requires tmpfs support"
+}
+
 # this test requires that (large) loopback device files are not in use
 #
 _require_no_large_scratch_dev()