netdev - Re: [PATCH bpf-next 1/4] bpf: Introduce bpf_skb_ancestor_cgroup

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Message-ID: <20180813153915.GA70723@rdna-mbp.dhcp.thefacebook.com>
Date:   Mon, 13 Aug 2018 08:39:15 -0700
From:   Andrey Ignatov <rdna@...com>
To:     Tejun Heo <tj@...nel.org>
CC:     <netdev@...r.kernel.org>, <ast@...nel.org>, <daniel@...earbox.net>,
        <guro@...com>, <kernel-team@...com>
Subject: Re: [PATCH bpf-next 1/4] bpf: Introduce bpf_skb_ancestor_cgroup_id
 helper

Tejun Heo <tj@...nel.org> [Mon, 2018-08-13 07:47 -0700]:
> Hello, Andrey.

Hey Tejun!

> 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;
> }

Sure, no problem. I'll send follow-up patch to simplify this part when
bpf-next is open again.

> 
> Thanks.
> 
> -- 
> tejun

-- 
Andrey Ignatov