--- cd30853bd230f778926cab735a7d85c49979082c
+++ ef6fdb0357e91fbb053ccfea5c643af980de0402
@@ -837,10 +837,11 @@ static const struct file_operations zero
 /*
  * capabilities for /dev/zero
  * - permits private mappings, "copies" are taken of the source of zeros
+ * - no writeback happens
  */
 static struct backing_dev_info zero_bdi = {
 	.name		= "char/mem",
-	.capabilities	= BDI_CAP_MAP_COPY,
+	.capabilities	= BDI_CAP_MAP_COPY | BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
 static const struct file_operations full_fops = {