- ret = bdrv_open(&s->qcow, s->qcow_filename, NULL, NULL,
- BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH,
- bdrv_qcow, errp);
+ options = qdict_new();
+ qdict_put(options, "driver", qstring_from_str("qcow"));
+ ret = bdrv_open(&s->qcow, s->qcow_filename, NULL, options,
+ BDRV_O_RDWR | BDRV_O_NO_FLUSH, errp);