qcow: Assign bs->file->bs to file in qcow_co_get_block_status

Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NFam Zheng <famz@redhat.com>
Message-id: 1453780743-16806-3-git-send-email-famz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

block/qcow.c

@@ -510,6 +510,7 @@ static int64_t coroutine_fn qcow_co_get_block_status(BlockDriverState *bs,
         return BDRV_BLOCK_DATA;
     }
     cluster_offset |= (index_in_cluster << BDRV_SECTOR_BITS);
+    *file = bs->file->bs;
     return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | cluster_offset;
 }