Re: [PATCH 1/8] cgroup: implement cgroup_is_ancestor()

Tejun Heo
2013-04-08T15:57:37Z

Hello,

On Mon, Apr 08, 2013 at 04:47:50PM +0200, Michal Hocko wrote:
> On Mon 08-04-13 16:20:11, Li Zefan wrote:
> [...]
> > @@ -5299,6 +5300,26 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
> > return css ? css : ERR_PTR(-ENOENT);
> > }
> >
> > +/**
> > + * cgroup_is_ancestor - test "root" cgroup is an ancestor of "child"
> > + * @child: the cgroup to be tested.
> > + * @root: the cgroup supposed to be an ancestor of the child.
> > + *
> > + * Returns true if "root" is an ancestor of "child" in its hierarchy.
> > + */
> > +bool cgroup_is_ancestor(struct cgroup *child, struct cgroup *root)
> > +{
> > + int depth = child->depth;
>
> Is this functionality helpful for other controllers but memcg?
> css_is_ancestor is currently used only by memcg code AFAICS and we can
> get the same functionality easily by using something like:

It's a basic hierarchy operation. I'd prefer it to be in cgroup and
in general let's try to avoid memcg-specific infrastructure. It
doesn't seem to end well.

Thanks.

--
tejun