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

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

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