diff --git a/fs/bio.c b/fs/bio.c
index 13be075..062299a 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -859,7 +859,7 @@
 	/*
 	 * success
 	 */
-	if (!write_to_vm) {
+	if (!write_to_vm && (!map_data || !map_data->null_mapped)) {
 		ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 0);
 		if (ret)
 			goto cleanup;