[libvirt] vm snapshot multi-disk

Marcus shadowsor at gmail.com
Thu Jul 16 05:51:30 UTC 2015


well, not *that* recently, I guess...

On Wed, Jul 15, 2015 at 10:51 PM, Marcus <shadowsor at gmail.com> wrote:

> 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
>> > >
>> >
>>
>>
>
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