block: implement bdrv_snapshot_goto for blkreplay

This patch enables making snapshots with blkreplay used in
block devices.
This function is required to make bdrv_snapshot_goto without
calling .bdrv_open which is not implemented.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/blkreplay.c

@@ -126,6 +126,12 @@ static int coroutine_fn blkreplay_co_flush(BlockDriverState *bs)
     return ret;
 }
 
+static int blkreplay_snapshot_goto(BlockDriverState *bs,
+                                   const char *snapshot_id)
+{
+    return bdrv_snapshot_goto(bs->file->bs, snapshot_id, NULL);
+}
+
 static BlockDriver bdrv_blkreplay = {
     .format_name            = "blkreplay",
     .instance_size          = 0,
@@ -140,6 +146,8 @@ static BlockDriver bdrv_blkreplay = {
     .bdrv_co_pwrite_zeroes  = blkreplay_co_pwrite_zeroes,
     .bdrv_co_pdiscard       = blkreplay_co_pdiscard,
     .bdrv_co_flush          = blkreplay_co_flush,
+
+    .bdrv_snapshot_goto     = blkreplay_snapshot_goto,
 };
 
 static void bdrv_blkreplay_init(void)