Re: [PATCH-cgroup v4] cgroup: Show # of subsystem CSSes in cgroup.stat

[Waiman Long]

On 7/26/24 16:40, Waiman Long wrote:
> On 7/26/24 04:19, Michal Koutný wrote:
> > > > > +	for_each_css(css, ssid, cgroup) {
> > > > > +		if ((BIT(ssid) & cgrp_dfl_inhibit_ss_mask) ||
> > > > > +		    (cgroup_subsys[ssid]->root !=  &cgrp_dfl_root))
> > > > > +			continue;
> > > > Is this taken? (Given cgroup.stat is only on the default hierarchy.)
> > > I am not sure what you are asking here. Since cgroup.stat is a cgroup v2
> > > only control file, it won't show subsystems that are bound to cgroup v1.
> > So, is the if (...) ever true? (The file won't exist on v1.)
>
> A mixed cgroup v1/v2 environment is allowed, though not encouraged. We 
> can have some cgroup controllers bound to cgroup v2 and the rests to 
> cgroup v1. It is in this case that cgroup.stat will only show those 
> that are with cgroup v2.
>
> Regards,
> Longman