[libvirt PATCH v2] Revert "cgroup/LXC: Do not condition availability of v2 by controllers"

[Daniel P. Berrangé]

On Tue, Oct 25, 2022 at 02:35:00PM +0200, Pavel Hrdina wrote:
> On Tue, Oct 25, 2022 at 01:13:44PM +0100, Daniel P. Berrangé wrote:
> > On Tue, Oct 25, 2022 at 01:46:22PM +0200, Michal Prívozník wrote:
> > > On 10/25/22 13:43, Pavel Hrdina wrote:
> > > > This reverts commit e49313b54ed2a149c71f9073659222742ff3ffb0.
> > > > This reverts commit a0f37232b9c4296ca16955cc625f75eb848ace39.
> > > > 
> > > > Revert them together to not break build.
> > > > 
> > > > This fix of the issue is incorrect and breaks usage of other controllers
> > > > in hybrid mode that systemd creates, specifically usage of devices and
> > > > cpuacct controllers as they are now assumed to be part of the cgroup v2
> > > > topology which is not true.
> > > > 
> > > > We need to find different solution to the issue.
> > > > 
> > > > Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> > > > ---
> > > >  src/util/vircgroup.c   |  6 ++----
> > > >  src/util/vircgroupv2.c | 15 +++++++++++++++
> > > >  2 files changed, 17 insertions(+), 4 deletions(-)
> > > 
> > > 
> > > Reviewed-by: Michal Privoznik <mprivozn at redhat.com>
> > > 
> > > This brings me back to my original proposal - let's forget that hybrid
> > > mode exist and aim on v1 or v2, solely.
> > 
> > FWIW, I thought that was already our intention. It has been recommended
> > to me by systemd maintainers that hybrid mode is best ignored.
> 
> The issue is that on systemd based distributions where you have v1 only
> it is technically hybrid setup where systemd uses v2 without any
> controller enabled for process tracking and that's the root cause of the
> issue that the original patch wanted to address.

Oh, that's the setup present in RHEL-8  IIUC, but I didn't consider
that to be hybrid, and yes we need to support that.

I considered hybrid to be when the resource controllers used a mix of
v1 and v2 attachment. Something people tried todo when some of the
controllers were not ported to v2 yet.

With regards,
Daniel
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