Re: vm snapshot multi-disk

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

On Wed, Jul 15, 2015 at 10:51 PM, Marcus <shadowsor@xxxxxxxxx> 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.


commit af957387547b05ed6dc4d84c10cca42700a7aeda
Author: Zhang Haoyu <zhanghy@xxxxxxxxxxx>
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@xxxxxxxx> wrote:


>>> On 7/14/2015 at 05:42 AM, in message
<CALFpzo551ioR=w5ASF7JXmtP8EgQSP2au_O6awmyofz9MfG3vg@xxxxxxxxxxxxxx>, Marcus
<shadowsor@xxxxxxxxx> 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@xxxxxxxxx> 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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