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

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

于 2013-6-19 15:46, Stefan Hajnoczi 写道:
> On Wed, Jun 19, 2013 at 02:18:48PM +0800, Wenchao Xia wrote:
>> 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.
>
> 'delvm' is a batch interface - it deletes internal snapshots that have
> the same name across multiple devices.
>
> It's not as flexible as:
> blkdev-internal-snapshot-delete drive0 drive2 drive4
>
> Because that would allow you to specify specific drives.
>
   Do you mean this interface should be changed as
blkdev-internal-snapshot-delete devices_array name *id?

   It seems not much difference with following methods:

for device in device_list:
   blkdev-internal-snapshot-delete device name


> Stefan
>


-- 
Best Regards

Wenchao Xia