Re: [Qemu-devel] [PATCH] let qemu-img info genereate json output

[Anthony Liguori <aliguori@us.ibm.com>]

"Daniel P. Berrange" <berrange@redhat.com> writes:

> On Fri, Jul 27, 2012 at 12:49:53PM +0200, Paolo Bonzini wrote:
>> Il 27/07/2012 12:33, Daniel P. Berrange ha scritto:
>> >  #qemu-img info -j /var/lib/libvirt/images/bar.qcow2
>> >  {
>> >     "information": {
>> >         "actual_size": "139264",
>> >         "fmt": "qcow2",
>> >         "virtual_size": "10485760",
>> >         "filename": "/var/lib/libvirt/images/bar.qcow2",
>> >         "cluster_size": 65536,
>> >         "encrypted": 0,
>> >         "snapshot_list": [
>> >         ],
>> >         "dirty_flag": 0,
>> >         "backing_filename": "/dev/sda1"
>> >     },
>> >     "return": 0
>> >  }
>> > 
>> > IIUC,the 'return' element here is just duplicating the qemu-img
>> > exit status. I think this is rather dubious, and would rather
>> > just see the stuff in the 'information' sub-block be output
>> > directly. It also seems to forget to mention the backing
>> > file format.
>> 
>> I wonder if we could add this also to the QEMU monitor ("info
>> block-image foo"), so that the code would be shared between qemu-img.c
>> and QEMU.
>
> It would certainly make sense to have the code & data format shared
> between the two, so apps don't need to have 2 different JSON parsers

We should definitely describe the output in qapi-schema.json.  Whether
we also expose a QMP command--I'm not really convinced.

It seems a bit unusual to me to want to get this info from an arbitrary
image file from within QEMU.  I'm not sure I see the use-case.

I can definitely see it become exposed as part of query-block though as
an image-info parameter.

Regards,

Anthony Liguori

>
>
> Daniel
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