Re: [PATCH v4 4/5] cgroup: use separate rstat trees for each subsystem

[JP Kobryn <inwardvessel@gmail.com>]

On 4/3/25 6:10 PM, JP Kobryn wrote:
>   __bpf_kfunc void css_rstat_flush(struct cgroup_subsys_state *css)
>   {
> -	struct cgroup *cgrp = css->cgroup;
>   	int cpu;
>   
>   	might_sleep();
>   	for_each_possible_cpu(cpu) {
> -		struct cgroup *pos;
> +		struct cgroup_subsys_state *pos;
>   
>   		/* Reacquire for each CPU to avoid disabling IRQs too long */
>   		__css_rstat_lock(css, cpu);
> -		pos = cgroup_rstat_updated_list(cgrp, cpu);
> +		pos = css_rstat_updated_list(css, cpu);
>   		for (; pos; pos = pos->rstat_flush_next) {
> -			struct cgroup_subsys_state *css;
> -
> -			cgroup_base_stat_flush(pos, cpu);
> -			bpf_rstat_flush(pos, cgroup_parent(pos), cpu);
> -
> -			rcu_read_lock();
> -			list_for_each_entry_rcu(css, &pos->rstat_css_list,
> -						rstat_css_node)
> +			if (css_is_cgroup(pos)) {
> +				cgroup_base_stat_flush(pos->cgroup, cpu);
> +				bpf_rstat_flush(pos->cgroup,
> +						cgroup_parent(pos->cgroup), cpu);
> +			} else if (pos->ss->css_rstat_flush)
>   				css->ss->css_rstat_flush(css, cpu);

This needs to change from css to pos. Note this was not an issue up
through v3. The flushing functions changed upstream between v3 and v4 so
this was possibly missed during the rebase.

> -			rcu_read_unlock();
>   		}
>   		__css_rstat_unlock(css, cpu);
>   		if (!cond_resched())