Introduce VIR_MIGRATE_ASSUME_SHARED_STORAGE

[libvirt PATCH 0/3] Introduce VIR_MIGRATE_ASSUME_SHARED_STORAGE

Posted by Andrea Bolognani 5 months, 4 weeks ago

This was initially motivated by a KubeVirt issue[1] concerning
integration with the Portworx storage provide, but it turns out to be
more generally applicable: since mounting an NFS share on the same
host that is exporting it is known to cause issues and is therefore
not recommended, we need a way to allow migration in such a
configuration while still not going quite as far as
VIR_MIGRATE_UNSAFE does and losing all handrails.

[1] https://issues.redhat.com/browse/CNV-34322

Andrea Bolognani (3):
  include: Introduce VIR_MIGRATE_ASSUME_SHARED_STORAGE
  qemu: Implement VIR_MIGRATE_ASSUME_SHARED_STORAGE support
  virsh: Wire up VIR_MIGRATE_ASSUME_SHARED_STORAGE support

 docs/manpages/virsh.rst          |  5 ++++-
 include/libvirt/libvirt-domain.h | 14 ++++++++++++++
 src/qemu/qemu_migration.c        |  5 +++++
 src/qemu/qemu_migration.h        |  1 +
 tools/virsh-domain.c             |  5 +++++
 5 files changed, 29 insertions(+), 1 deletion(-)

-- 
2.41.0

Re: [libvirt PATCH 0/3] Introduce VIR_MIGRATE_ASSUME_SHARED_STORAGE

Posted by Peter Krempa 5 months, 4 weeks ago

On Tue, Oct 31, 2023 at 18:12:57 +0100, Andrea Bolognani wrote:
> This was initially motivated by a KubeVirt issue[1] concerning
> integration with the Portworx storage provide, but it turns out to be
> more generally applicable: since mounting an NFS share on the same
> host that is exporting it is known to cause issues and is therefore
> not recommended, we need a way to allow migration in such a
> configuration while still not going quite as far as
> VIR_MIGRATE_UNSAFE does and losing all handrails.
> 
> [1] https://issues.redhat.com/browse/CNV-34322
> 
> Andrea Bolognani (3):
>   include: Introduce VIR_MIGRATE_ASSUME_SHARED_STORAGE
>   qemu: Implement VIR_MIGRATE_ASSUME_SHARED_STORAGE support
>   virsh: Wire up VIR_MIGRATE_ASSUME_SHARED_STORAGE support

Reviewed-by: Peter Krempa <pkrempa@redhat.com>

but please add some wording being more explicit about the need for the
storage to be still shared. While it's implied in all places users tend
to ignore any non-obvious messaging.

Re: [libvirt PATCH 0/3] Introduce VIR_MIGRATE_ASSUME_SHARED_STORAGE

Posted by Daniel P. Berrangé 5 months, 4 weeks ago

On Wed, Nov 01, 2023 at 01:42:07PM +0100, Peter Krempa wrote:
> On Tue, Oct 31, 2023 at 18:12:57 +0100, Andrea Bolognani wrote:
> > This was initially motivated by a KubeVirt issue[1] concerning
> > integration with the Portworx storage provide, but it turns out to be
> > more generally applicable: since mounting an NFS share on the same
> > host that is exporting it is known to cause issues and is therefore
> > not recommended, we need a way to allow migration in such a
> > configuration while still not going quite as far as
> > VIR_MIGRATE_UNSAFE does and losing all handrails.
> > 
> > [1] https://issues.redhat.com/browse/CNV-34322
> > 
> > Andrea Bolognani (3):
> >   include: Introduce VIR_MIGRATE_ASSUME_SHARED_STORAGE
> >   qemu: Implement VIR_MIGRATE_ASSUME_SHARED_STORAGE support
> >   virsh: Wire up VIR_MIGRATE_ASSUME_SHARED_STORAGE support
> 
> Reviewed-by: Peter Krempa <pkrempa@redhat.com>
> 
> but please add some wording being more explicit about the need for the
> storage to be still shared. While it's implied in all places users tend
> to ignore any non-obvious messaging.

I don't think we should be adding this flag, but instead provide a way
for an host admin to express to libvirt which local paths are exported
to other hosts and also detect this from /etc/exports where available.

With regards,
Daniel
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