Am 14.05.2010 11:51, schrieb MORITA Kazutaka: > When snapshot handlers of the format driver is not defined, it is > better to call the ones of the protocol driver. > > This enables us to implement snapshot support in the protocol driver. > > Signed-off-by: MORITA Kazutaka <morita.kazut...@lab.ntt.co.jp>
> int bdrv_snapshot_goto(BlockDriverState *bs, > @@ -1737,9 +1743,11 @@ int bdrv_snapshot_goto(BlockDriverState *bs, > BlockDriver *drv = bs->drv; > if (!drv) > return -ENOMEDIUM; > - if (!drv->bdrv_snapshot_goto) > - return -ENOTSUP; > - return drv->bdrv_snapshot_goto(bs, snapshot_id); > + if (drv->bdrv_snapshot_goto) > + return drv->bdrv_snapshot_goto(bs, snapshot_id); > + if (bs->file) > + return bdrv_snapshot_goto(bs->file, snapshot_id); > + return -ENOTSUP; > } During lunch one more thing came to my mind... For bdrv_snapshot_goto it's probably not that easy for formats other than raw. Usually the drivers keep some state in memory, and with this code they won't re-read it after the snapshot has been loaded - which will lead to an inconsistent state very easily. I think the right thing to do here is: 1. Call drv->bdrv_close() so that the format driver cleans up, but the underlying protocol stays open 2. Load the snapshot on the protocol level 3. Call drv->bdrv_open() to load the new state The other functions in this patch should be okay without re-opening because they don't change the current state. Kevin
