Re: [Qemu-devel] [PATCH V6 11/14] qmp: add interface query-snapshots

[Eric Blake]

On 02/18/2013 03:46 PM, Wenchao Xia wrote:
> Hi, Eric
>   About the interface,there is actually requirement to know internal
> snapshots in an image of a backing file, so I think the API should be
> improved as:
> 
> # @query-snapshots:
> #
> # Get a list of internal snapshots for whole virtual machine or a single
> # block device. Note that in first case, only valid internal snapshot
> # will be returned, inconsistent ones will be ignored.
> #
> # @device: #optional the name of the device to get snapshot info from. #
>          If not specified, only valid snapshots for whole vm would be
> #          returned.
> # @image: #optional the image's name in the backing chain, only valid
> #          when device is specified. If it is not specified, the
> #          internal snapshots on the top of the chain will be shown.
> #          Otherwise qemu will try search the image on the chain on
> #          that device.

Why not just always show all information for all images in the chain?
Is it an efficiency issue, where allowing the user to limit information
up front will result in a more responsive command?  If that is not a
concern, then making the command simpler by having just a @device
argument, and no @image argument, seems like the better way to go.

But I definitely agree that if you have:

base.qcow2 <- top.qcow2

and both base.qcow2 and top.qcow2 each contain internal snapshots, that
there should be a way to get at all of that information, and not be
limited to just the information on the internal snapshots in top.qcow2.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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