block/commit: use buffer-based io

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/commit.c

@@ -48,16 +48,15 @@ static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
                                         void *buf)
 {
     int ret = 0;
-    QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
 
     assert(bytes < SIZE_MAX);
 
-    ret = blk_co_preadv(bs, offset, qiov.size, &qiov, 0);
+    ret = blk_co_pread(bs, offset, bytes, buf, 0);
     if (ret < 0) {
         return ret;
     }
 
-    ret = blk_co_pwritev(base, offset, qiov.size, &qiov, 0);
+    ret = blk_co_pwrite(base, offset, bytes, buf, 0);
     if (ret < 0) {
         return ret;
     }