Re: [PATCH bpf-next v2 4/8] bpf: Introduce cgroup iter

Hao Luo
2022-07-07T23:36:23Z

On Mon, Jun 27, 2022 at 9:14 PM Yonghong Song <yhs@fb.com> wrote:
>
> > +static int __cgroup_iter_seq_show(struct seq_file *seq,
> > + struct cgroup_subsys_state *css, int in_stop)
> > +{
> > + struct cgroup_iter_priv *p = seq->private;
> > + struct bpf_iter__cgroup ctx;
> > + struct bpf_iter_meta meta;
> > + struct bpf_prog *prog;
> > + int ret = 0;
> > +
> > + /* cgroup is dead, skip this element */
> > + if (css && cgroup_is_dead(css->cgroup))
> > + return 0;
> > +
> > + ctx.meta = &meta;
> > + ctx.cgroup = css ? css->cgroup : NULL;
> > + meta.seq = seq;
> > + prog = bpf_iter_get_info(&meta, in_stop);
> > + if (prog)
> > + ret = bpf_iter_run_prog(prog, &ctx);
>
> Do we need to do anything special to ensure bpf program gets
> up-to-date stat from ctx.cgroup?
>

Let's leave that to be handled by bpf programs. The kfunc rstat_flush
can be called to sync stats, if using rstat.

> > +
> > + /* if prog returns > 0, terminate after this element. */
> > + if (ret != 0)
> > + p->terminate = true;
> > +
> > + return 0;
> > +}
> > +
> …