--- x/block/blk-map.c
+++ y/block/blk-map.c
@@ -48,7 +48,9 @@ static int bio_copy_from_iter(struct bio
 {
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
+	bool data_source = iter->data_source;
 
+	iter->data_source = true;
 	bio_for_each_segment_all(bvec, bio, iter_all) {
 		ssize_t ret;
 
@@ -60,9 +62,12 @@ static int bio_copy_from_iter(struct bio
 		if (!iov_iter_count(iter))
 			break;
 
-		if (ret < bvec->bv_len)
+		if (ret < bvec->bv_len) {
+			iter->data_source = data_source;
 			return -EFAULT;
+		}
 	}
+	iter->data_source = data_source;
 
 	return 0;
 }