Re: [Qemu-devel] Re: [PATCH] monitor: Really show snapshot information about all devices

[Kevin Wolf <kwolf@redhat.com>]

Am 16.06.2010 17:22, schrieb Chris Lalancette:
> On 06/16/10 - 03:15:11PM, Kevin Wolf wrote:
>> Am 16.06.2010 14:59, schrieb Miguel Di Ciurcio Filho:
>>> On Wed, Jun 16, 2010 at 9:40 AM, Kevin Wolf <kwolf@redhat.com> wrote:
>>>>
>>>> If the human monitor was exactly what its name says, I'd happily apply
>>>> this one (though I think it should be made clear from which image the VM
>>>> state would be loaded). However, it isn't and I'm not sure if this
>>>> wouldn't break libvirt. Dan, can you help?
>>>>
>>>
>>> I didn't mention in the commit, but I've looked at libvirt's source
>>> and it is not using 'info snapshots' AFAIK.
>>
>> Anthony, Dan, are you okay with the change then?
> 
> Right, exactly as Miguel said, libvirt doesn't use "info snapshots" at all
> at the moment.  One of the reasons we don't use it at present is precisely
> because it doesn't give us information about all disks in-use.
> 
> The other reason that we can't use "info snapshots" is that we need to know
> parent information about snapshots. That is, if you take a sequence of
> snapshots:
> 
> A -> B -> C
> 
> And then you delete B, the disk changes from B will be merged automatically
> into C to keep C a valid snapshot.  However, there is currently no way to
> discover this parent/child relationship, so we can't use "info snapshots"
> for that reason as well.

Well, there is no parent/child relation in qcow2, so exposing this is
going to be really hard. We also don't really need it anywhere in qemu.
What would libvirt use this information for?

Kevin