block/parallels: use QEMU_IOVEC_INIT_BUF

Use new QEMU_IOVEC_INIT_BUF() instead of
qemu_iovec_init_external( ... , 1), which simplifies the code.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20190218140926.333779-8-vsementsov@virtuozzo.com
Message-Id: <20190218140926.333779-8-vsementsov@virtuozzo.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/parallels.c

@@ -220,23 +220,20 @@ 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;
+        QEMUIOVector qiov =
-        struct iovec iov = {
+            QEMU_IOVEC_INIT_BUF(qiov, qemu_blockalign(bs, nb_cow_bytes),
-            .iov_len = nb_cow_bytes,
+                                nb_cow_bytes);
-            .iov_base = qemu_blockalign(bs, nb_cow_bytes)
-        };
-        qemu_iovec_init_external(&qiov, &iov, 1);
 
         ret = bdrv_co_preadv(bs->backing, idx * s->tracks * BDRV_SECTOR_SIZE,
                              nb_cow_bytes, &qiov, 0);
         if (ret < 0) {
-            qemu_vfree(iov.iov_base);
+            qemu_vfree(qemu_iovec_buf(&qiov));
             return ret;
         }
 
         ret = bdrv_co_pwritev(bs->file, s->data_end * BDRV_SECTOR_SIZE,
                               nb_cow_bytes, &qiov, 0);
-        qemu_vfree(iov.iov_base);
+        qemu_vfree(qemu_iovec_buf(&qiov));
         if (ret < 0) {
             return ret;
         }