Re: [Qemu-devel] [PATCH V9 00/14] qmp/hmp interfaces for internal snapshot info

[Stefan Hajnoczi]

On Wed, Mar 13, 2013 at 10:54:50AM +0800, Wenchao Xia wrote:
> 于 2013-3-13 0:16, Eric Blake 写道:
> >On 03/12/2013 04:07 AM, Stefan Hajnoczi wrote:
> >>On Mon, Mar 11, 2013 at 07:23:02PM +0800, Wenchao Xia wrote:
> >>>   In the use of snapshot a way to retrieve related info at runtime is 
> >>> needed,
> >>>so this serial of patches will merge some code for qemu and qemu-img, and 
> >>>add
> >>>following interfaces for qemu:
> >>>
> >
> >>Is there a reason you added the new query-images command instead of
> >>extending BlockDeviceInfo with an ImageInfo field?  Then query-block,
> >>which is already used today, just provides ImageInfo as well.
> >>
> >>I suggest this because it makes life easier for clients - they can issue
> >>a single command to extract all image information.  If we have two
> >>commands they may have to invoke both and then match the results
> >>together.
> >
> >Indeed, from the libvirt perspective, I would much prefer that a single
> >command gives me everything, instead of having to call two commands to
> >build up the complete picture.
> >
> 
>   I have no special reason for new interface query-images, it just
> show up during the work, and I am pretty OK to merge the information
> into query-block especially when the user of it, Eric hope so. Then
> the qmp interface need to designed carefully, my idea is adding an item
> in  BlockDeviceInfo:
> 
> { 'type': 'BlockDeviceInfo',
>   'data': { 'file': 'str', 'ro': 'bool', 'drv': 'str',
>             '*backing_file': 'str', 'backing_file_depth': 'int',
>             'encrypted': 'bool', 'encryption_key_missing': 'bool',
>             'bps': 'int', 'bps_rd': 'int', 'bps_wr': 'int',
>             'iops': 'int', 'iops_rd': 'int', 'iops_wr': 'int',
>             'images': ['ImageInfo']} }}
> 
>   In this way, new define of structure is not needed, and no break
> of API I guess, but disadvantage is there will be some duplicated info
> in ImageInfo and other structure in BlockInfo, such as "file,
> encrypted".

I'm happy with adding a ImageInfo field into BlockDeviceInfo.

Why did you make it an array and what is the array's layout?

Stefan