[libvirt] vm snapshot multi-disk

Marcus shadowsor at gmail.com
Thu Jul 16 05:51:05 UTC 2015


I tracked it down. Found it was introduced in 1.7.0 and patched recently in
qemu-kvm. Your version might have the fix backported, qemu-kvm-ev 2.1.2
from redhat/centos/fedora doesn't.

Libvirt sends a 'delvm <snapshotid>' to the qemu monitor via HMP, and Qemu,
instead of looping over all disks, repeatedly looped over the first one.

Thanks for looking at it.

https://bugzilla.redhat.com/show_bug.cgi?id=1243102

commit af957387547b05ed6dc4d84c10cca42700a7aeda
Author: Zhang Haoyu <zhanghy at sangfor.com>
Date:   Mon Sep 29 16:38:02 2014 +0800

    snapshot: fix referencing wrong variable in while loop in do_delvm

    The while loop variabal is "bs1",
    but "bs" is always passed to bdrv_snapshot_delete_by_id_or_name.
    Broken in commit a89d89d, v1.7.0.



On Wed, Jul 15, 2015 at 7:26 PM, Chun Yan Liu <cyliu at suse.com> wrote:

>
>
> >>> On 7/14/2015 at 05:42 AM, in message
> <CALFpzo551ioR=w5ASF7JXmtP8EgQSP2au_O6awmyofz9MfG3vg at mail.gmail.com>,
> Marcus
> <shadowsor at gmail.com> wrote:
> > Oh, I almost forgot to mention the versions:
> >
> > libvirt 1.2.8-16.0.1.el7_1.2.x86_64
> >
> > qemu 2.1.2-23.el7_1.1.x86_64
>
> Just FYI, tested on my machine, libvirt 1.2.5, qemu 2.0.0, didn't see this
> problem.
> Both disk snapshots are deleted.
>
> >
> >
> > Also, I'm unclear if the domain snapshot feature is orchestralted by
> > libvirt, or something that is simply called into qemu to take care of.
> > Please forgive me if this is a qemu issue.
> >
> > On Mon, Jul 13, 2015 at 2:35 PM, Marcus <shadowsor at gmail.com> wrote:
> >
> > > Hi all,
> > >
> > >     I've recently been toying with VM snapshots, and have ran into an
> > > issue. Given a VM with multiple disks, it seems a snapshot-create
> followed
> > > by a snapshot-delete will only remove the qcow2 snapshot for the first
> disk
> > > (or perhaps just the disk that contains the memory), not all of the
> disk
> > > snapshots it created. Is this something people are aware of?
> > >
> > >     In searching around, I found a bug report where snapshot-creates
> would
> > > fail due to the qcow2 snapshot ids being inconsistent. That looks like
> it
> > > is patched for 2.4 qemu (
> > > http://lists.nongnu.org/archive/html/qemu-devel/2015-03/msg04963.html
> ),
> > > this bug would trigger that one by leaving IDs around that are
> inconsistent
> > > between member disks, but is not the same.
> > >
> > > # virsh snapshot-create 7
> > >
> > > Domain snapshot 1436792720 created
> > >
> > >
> > > # virsh snapshot-list 7
> > >
> > >  Name                 Creation Time             State
> > >
> > > ------------------------------------------------------------
> > >
> > >  1436792720           2015-07-13 06:05:20 -0700 running
> > >
> > >
> > > # virsh domblklist 7
> > >
> > > Target     Source
> > >
> > > ------------------------------------------------
> > >
> > > vda
> > >
> >
> /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/e4d6e885-1382-40bc-890b-ad9c8b51a7a
> > 5
> > >
> > > vdb
> > >
> >
> /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/7033e4c6-5f59-4325-b7e0-ae191e12e86
> > c
> > >
> > >
> > > # qemu-img snapshot -l
> > >
> >
> /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/e4d6e885-1382-40bc-890b-ad9c8b51a7a
> > 5
> > >
> > > Snapshot list:
> > >
> > > ID        TAG                 VM SIZE                DATE       VM
> CLOCK
> > >
> > > 1         1436792720             173M 2015-07-13 06:05:20
>  00:01:10.938
> > >
> > >
> > > # qemu-img snapshot -l
> > >
> >
> /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/7033e4c6-5f59-4325-b7e0-ae191e12e86
> > c
> > >
> > > Snapshot list:
> > >
> > > ID        TAG                 VM SIZE                DATE       VM
> CLOCK
> > >
> > > 1         1436792720                0 2015-07-13 06:05:20
>  00:01:10.938
> > >
> > >
> > > # virsh snapshot-delete 7 1436792720
> > >
> > > Domain snapshot 1436792720 deleted
> > >
> > >
> > > # qemu-img snapshot -l
> > >
> >
> /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/e4d6e885-1382-40bc-890b-ad9c8b51a7a
> > 5
> > >
> > > # qemu-img snapshot -l
> > >
> >
> /mnt/2a270ef3-f389-37a4-942f-380bed9f70aa/7033e4c6-5f59-4325-b7e0-ae191e12e86
> > c
> > >
> > > Snapshot list:
> > >
> > > ID        TAG                 VM SIZE                DATE       VM
> CLOCK
> > >
> > > 1         1436792720                0 2015-07-13 06:05:20
>  00:01:10.938
> > >
> >
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20150715/1f1cb2fb/attachment-0001.htm>


More information about the libvir-list mailing list