Bug#1108294: [PATCH 4/4] cgroup: Do not report unavailable v1 controllers in /proc/cgroups

[Tejun Heo <tj@kernel.org>]

On Fri, Jul 11, 2025 at 03:10:44PM +0200, Michal Koutný wrote:
> Hello Ben.
> 
> On Wed, Jul 09, 2025 at 08:22:09PM +0200, Ben Hutchings <ben@decadent.org.uk> wrote:
> > Would you consider reverting this change for the sake of compatibility?
> 
> As you write, it's not fatally broken and it may be "just" an issue of
> container images that got no fresh rebuild. (And I think it should be
> generally discouraged running containers with stale deps in them.)
> 
> The original patch would mainly serve legacy userspace (host) setups on
> top of contemporary kernel (besides API purity reasons). Admittedly,
> these should be rare and eventually extinct in contrast with your
> example where it's a containerized userspace (which typically could do
> no cgroup setup) that may still have some user demand.
> 
> So, I'd be more confident with the revert if such an adjustment was
> carried downstream by some distro and proven its viability first. Do you
> know of any in the wild?

I think we still want to deprecate /proc/cgroups but given that there are
impacted users maybe we can bring it back under a boottime param w/ warning?

Thanks.

-- 
tejun