Re: [PATCH v2 2/2] vmscan,cgroup: apply mems_effective to reclaim

[Gregory Price <gourry@gourry.net>]

On Fri, Apr 18, 2025 at 10:06:40PM -0400, Waiman Long wrote:
> > +bool cpuset_node_allowed(struct cgroup *cgroup, int nid)
> > +{
> > +	struct cgroup_subsys_state *css;
> > +	unsigned long flags;
> > +	struct cpuset *cs;
> > +	bool allowed;
> > +
> > +	css = cgroup_get_e_css(cgroup, &cpuset_cgrp_subsys);
> > +	if (!css)
> > +		return true;
> > +
> > +	cs = container_of(css, struct cpuset, css);
> > +	spin_lock_irqsave(&callback_lock, flags);
> > +	/* At least one parent must have a valid node list */
> > +	while (nodes_empty(cs->effective_mems))
> > +		cs = parent_cs(cs);
> 
> For cgroup v2, effective_mems should always be set and walking up the tree
> isn't necessary. For v1, it can be empty, but memory cgroup and cpuset are
> unlikely in the same hierarchy.
> 

Hm, do i need different paths here for v1 vs v2 then?  Or is it
sufficient to simply return true if effective_mems is empty (which
implies v1)?

Thanks,
~Gregory