block/parallels: use buffer-based io

Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/parallels.c

@@ -220,20 +220,18 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
     if (bs->backing) {
         int64_t nb_cow_sectors = to_allocate * s->tracks;
         int64_t nb_cow_bytes = nb_cow_sectors << BDRV_SECTOR_BITS;
-        QEMUIOVector qiov =
-            QEMU_IOVEC_INIT_BUF(qiov, qemu_blockalign(bs, nb_cow_bytes),
-                                nb_cow_bytes);
+        void *buf = qemu_blockalign(bs, nb_cow_bytes);
 
-        ret = bdrv_co_preadv(bs->backing, idx * s->tracks * BDRV_SECTOR_SIZE,
-                             nb_cow_bytes, &qiov, 0);
+        ret = bdrv_co_pread(bs->backing, idx * s->tracks * BDRV_SECTOR_SIZE,
+                            nb_cow_bytes, buf, 0);
         if (ret < 0) {
-            qemu_vfree(qemu_iovec_buf(&qiov));
+            qemu_vfree(buf);
             return ret;
         }
 
         ret = bdrv_co_pwritev(bs->file, s->data_end * BDRV_SECTOR_SIZE,
-                              nb_cow_bytes, &qiov, 0);
-        qemu_vfree(qemu_iovec_buf(&qiov));
+                              nb_cow_bytes, buf, 0);
+        qemu_vfree(buf);
         if (ret < 0) {
             return ret;
         }