libvirt users - May 2020 - Re: blockcommit --pivot does not succeed in conjunction with qemu 5.0.0

Hello one and all.

Got a problem with libvirt 6.2.0 and qemu 5.0.0.

virsh blockcommit mymachine vda --active --verbose --pivot

works until it shows [100%] but it never actually pivots. It just sits 
there. Is this a known issue with 6.2.0 and i should
try 6.3.0? For now i switched back to qemu 4.2.0 and this seems to solve 
the issue too. Any hints?

Ahoi! t.

Maybe:

from 6.3.0 release notes:

- qemu: Fix domain restore from a block device
     When using namespaces, libvirt was unable to restore a domain from a 
block device because libvirt tried to relabel the device inside the 
namespace while QEMU was given FD to the block device in the host.

cheers, t.

On 2020-05-08 12:48, Thomas Stein wrote:
> Hello one and all.
> 
> Got a problem with libvirt 6.2.0 and qemu 5.0.0.
> 
> virsh blockcommit mymachine vda --active --verbose --pivot
> 
> works until it shows [100%] but it never actually pivots. It just sits
> there. Is this a known issue with 6.2.0 and i should
> try 6.3.0? For now i switched back to qemu 4.2.0 and this seems to
> solve the issue too. Any hints?
> 
> Ahoi! t.

On Fri, May 08, 2020 at 13:05:01 +0200, Thomas Stein
wrote:
> 
> Maybe:
> 
> from 6.3.0 release notes:
> 
> - qemu: Fix domain restore from a block device
>     When using namespaces, libvirt was unable to restore a domain from a
> block device because libvirt tried to relabel the device inside the
> namespace while QEMU was given FD to the block device in the host.
This is not relevant to block commit in any way.

> 
> cheers, t.
> 
> On 2020-05-08 12:48, Thomas Stein wrote:
> > Hello one and all.
> > 
> > Got a problem with libvirt 6.2.0 and qemu 5.0.0.
> > 
> > virsh blockcommit mymachine vda --active --verbose --pivot
> > 
> > works until it shows [100%] but it never actually pivots. It just sits
> > there. Is this a known issue with 6.2.0 and i should
> > try 6.3.0? For now i switched back to qemu 4.2.0 and this seems to
> > solve the issue too. Any hints?
It's hard to tell from this description. It's certainly not something
I've heard of. Both qemu-5.0 and qemu-4.2 allow libvirt to use -blockdev
way to configure disks where a lot changed compared to previous versions
but since those two versions both use blockdev it should work the same.

It kind of looks as a problem in qemu but can't tell more without debug
logs.

Please follow the steps here https://wiki.libvirt.org/page/DebugLogs and
reproduce the bug. I can then look at the log file and see whether I see
some anomalies.