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

[Wenchao Xia]

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".

--
Best Regards

Wenchao Xia