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Re: [Qemu-devel] [PATCH v13 00/14] Drop in_use from BlockDriverState and
From: |
Ian Main |
Subject: |
Re: [Qemu-devel] [PATCH v13 00/14] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD |
Date: |
Sat, 1 Feb 2014 17:13:11 -0800 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sat, Feb 01, 2014 at 11:21:17PM +0800, Fam Zheng wrote:
> On Fri, 01/31 19:00, Ian Main wrote:
> > On Wed, Jan 29, 2014 at 01:07:27PM +0800, Fam Zheng wrote:
> > > This series adds for point-in-time snapshot NBD exporting based on
> > > blockdev-backup (variant of drive-backup with existing device as target).
> > >
> > > We get a thin point-in-time snapshot by COW mechanism of drive-backup, and
> > > export it through built in NBD server. The steps are as below:
> > >
> > > 1. (SHELL) qemu-img create -f qcow2 BACKUP.qcow2 <source size here>
> > >
> > > (Alternatively we can use -o backing_file=RUNNING-VM.img to omit
> > > explicitly
> > > providing the size by ourselves, but it's risky because
> > > RUNNING-VM.qcow2 is
> > > used r/w by guest. Whether or not setting backing file in the image
> > > file
> > > doesn't matter, as we are going to override the backing hd in the next
> > > step)
> > >
> > > 2. (QMP) blockdev-add backing=source-drive file.driver=file
> > > file.filename=BACKUP.qcow2 id=target0 if=none driver=qcow2
> >
> > It seems like we have a regression here. I sent you a private email
> > earlier and after some more testing I am finding that the setup that I
> > had to test this before is no longer working. Now when I try to use
> > blockdev-add I get:
> >
> > rsp = srv.cmd(command, {'options': {
> > 'backing': 'ide0-hd0',
> > 'driver': 'qcow2',
> > 'id': 'target0',
> > 'file': {
> > 'driver': 'file',
> > 'filename': '/home/imain/tmp/BACKUP.qcow2'
> > }
> > }
> > })
> >
> > rsp is {u'error': {u'class': u'GenericError', u'desc': u"could not open
> > disk image target0: Block format 'qcow2' used by device 'target0'
> > doesn't support the option 'backing'"}}
> >
> > It's possible I'm messing something up but I'm pretty sure something has
> > changed with the options handling in bdrv_open() to make this not work
> > anymore.
> >
>
> My local test script is very similar to this, so as the case added in this
> series. They both work here. Have you found what is wrong there yet?
Hrrm, so I cleaned up my tree, pulled to latest and applied these and it
worked. Not sure what happened there but it all seems good now. I
should have tried that before I posted.
Ian