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? Fam