Re: [PATCH bpf-next 1/4] bpf: Introduce bpf_skb_ancestor_cgroup_id helper

[Tejun Heo <tj@kernel.org>]

Hello, Andrey.

On Fri, Aug 10, 2018 at 10:35:23PM -0700, Andrey Ignatov wrote:
> +static inline struct cgroup *cgroup_ancestor(struct cgroup *cgrp,
> +					     int ancestor_level)
> +{
> +	struct cgroup *ptr;
> +
> +	if (cgrp->level < ancestor_level)
> +		return NULL;
> +
> +	for (ptr = cgrp;
> +	     ptr && ptr->level > ancestor_level;
> +	     ptr = cgroup_parent(ptr))
> +		;
> +
> +	if (ptr && ptr->level == ancestor_level)
> +		return ptr;
> +
> +	return NULL;
> +}

I don't have any objections functionanlity-wise but can we do sth like
the following instead?

static inline struct cgroup *cgroup_ancestor(struct cgroup *cgrp,
					     int ancestor_level)
{
	if (cgrp->level < ancestor_level)
		return NULL;

	while (cgrp->level > ancestor_level)
		cgrp = cgroup_parent(cgrp);
	return cgrp;
}

Thanks.

-- 
tejun