Re: [Qemu-devel] [PATCH V2 09/12] qmp: add interface blockdev-snapshot-delete-internal-sync

[Wenchao Xia]

于 2013-6-18 22:20, Stefan Hajnoczi 写道:
> On Mon, Jun 17, 2013 at 11:25:26AM +0800, Wenchao Xia wrote:
> > 于 2013-6-15 17:55, Eric Blake 写道:
> > > Should this command be made available via 'transaction'?  That is, if I
> > > have a two-disk VM, and use 'transaction' to take a snapshot of both
> > > disks at once, shouldn't I also have a way to delete the snapshots of
> > > both at once, or gracefully fail without data loss if the second one has
> > > problems?
> >
> >    I think adding it in transaction is not very useful but brings more
> > complexity. Transcation is used to guareentee all operations are taken
> > in one time point, for example, snapshot creation use it to make sure
> > all are consistent to VM. But for deletion, this requirement do not
> > exist.
>
> I guess the problem is: can we make internal snapshot deletion
> transactional?  It's hard to do rollback for snapshot deletion.
  Several deletion in transaction equals to several calls of
'blockdev-snapshot-delete-internal-sync', unlike creation, so I hope
not add it which have rollback issue.


> But batching is definitely useful for doing 'delvm' in QMP.  I just
> don't think transactions help.  We just need a 'delvm' equivalent in
> QMP.
  Maybe the caller can encapsulate a batch interface at its level.

> Stefan


--
Best Regards

Wenchao Xia