On Wed, Dec 11, 2013 at 10:46:49AM +0800, Fam Zheng wrote: > On 2013年11月28日 16:39, 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 > > > > (where ide0-hd0 is the running BlockDriverState name for > > RUNNING-VM.img. This patch implements "backing=" option to override > > backing_hd for added drive) > > > > 3. (QMP) blockdev-backup device=source-drive sync=none target=target0 > > > > (this is the QMP command introduced by this series, which use a named > > device as target of drive-backup) > > > > 4. (QMP) nbd-server-add device=target0 > > > >When image fleecing done: > > > > 1. (QMP) block-job-complete device=ide0-hd0 > > > > 2. (HMP) drive_del target0 > > > > 3. (SHELL) rm BACKUP.qcow2 > > > >v6: Address Paolo's comments, (except for bitmask): > > - Add blocker for all backing_hd references, a relatively big change, > > some > > patches are reordered. > > - Introduce a few other necessary patches. > > - Move two snapshot checks into bdrv_snapshot_*. > > > > The interface is unchanged. > > > > Hi, > > Based on the size of change, this series needs some more review > before merging. And I'd like to know if there is any concern or > objection with op_blocker introduced here. I would like to base my > next series (incremental backup with dirty bitmap) on it. > > Any more reviews/comments?
I really like it. Just did some more testing and this seems to have solved the issues from before.. I suspect this will resolve some issues with other commands and will be a useful framework for the future. I love this: (qemu) drive_del target0 block device is in use by block job: backup (qemu) drive_del target1 block device is in use by block job: backup (qemu) drive_del ide0-hd0 device is used as backing hd of 'target0' $ python qmp --path=/home/imain/qmp-sock eject --device=target0 <snip> Exception: block device is in use by block job: backup I've started working on a backup/snapshot API for libvirt already. Ian