Re: [PATCH 4/5] cgroup: distinguish the default and legacy hierarchies when handling cftypes

[Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

> @@ -3085,8 +3091,37 @@ static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
>  	return ret;
>  }
>  
> +/**
> + * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
> + * @ss: target cgroup subsystem
> + * @cfts: zero-length name terminated array of cftypes
> + *
> + * Similar to cgroup_add_cftypes() but the added files are only used for
> + * the default hierarchy.
> + */
> +int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
> +{
> +	struct cftype *cft;
> +
> +	for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
> +		cft->flags |= CFTYPE_ONLY_ON_DFL;

I think we should remove this flag in cgroup_rm_cftypes_locked(). Otherwise
if we call cgroup_add_dlf_cftypes() and then cgroup_rm_cftypes() and then
cgroup_add_legacy_cftypes() for the same @cfts, both CFTYPE_ONLY_ON_DFL and
CFTYPE_INSANE are set.

> +	return cgroup_add_cftypes(ss, cfts);
> +}
> +
> +/**
> + * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
> + * @ss: target cgroup subsystem
> + * @cfts: zero-length name terminated array of cftypes
> + *
> + * Similar to cgroup_add_cftypes() but the added files are only used for
> + * the legacy hierarchies.
> + */
>  int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
>  {
> +	struct cftype *cft;
> +
> +	for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
> +		cft->flags |= CFTYPE_INSANE;
>  	return cgroup_add_cftypes(ss, cfts);
>  }