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Date: Tue, 21 Apr 2015 16:48:50 +0200
From: Kashyap Chamarthy <kchamart@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2.5 00/10] block: incremental backup
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To: John Snow <jsnow@redhat.com>
Cc: kwolf@redhat.com, famz@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, mreitz@redhat.com, vsementsov@parallels.com, stefanha@redhat.com

On Tue, Apr 21, 2015 at 03:53:11PM +0200, Kashyap Chamarthy wrote:

[. . .]

> And, invoking `drive-backup` *without* pre-creating the target image
> (i.e. 'incremental.o.img'):
> 
>     { 'execute': 'drive-backup',
>       'arguments': {
>         'device': 'ide0-0-0',

Small typo (in this email, not in my test): s/ide0-0-0/drive-ide0-0-0

>         'bitmap': 'bitmap0',
>         'sync': 'dirty-bitmap',
>         'target': 'incremental.0.img',
>         'mode': 'existing',
>         'format': 'qcow2'
>       }
>     }
> 
> Results in:
> 
>     {"QMP": {"version": {"qemu": {"micro": 93, "minor": 2, "major": 2},
>     "package": ""}, "capabilities": []}} {"return": {}}
> 
> Instead of an "error". Is this a bug?
> 
> On a related note, Kevin Wolf said on IRC that he gets an error
> (without 'bitmap') when tested from QEMU master branch.

On a separate machine, I tested the above behavior with master
(f2a5810), but I don't see any error, without 'bitmap' and with 'mode'
as 'existing', i.e.:

  { 'execute': 'drive-backup', 'arguments':
        { 'device': 'drive-virtio-disk0', 'sync': 'full', 'target':
        '/var/lib/libvirt/images/incremental.0.img', 'mode': 'existing', 'format': 'qcow2' } }

still results in:

    {"return": {}}

Maybe I doing something wrong?

-- 
/kashyap