netdev - Re: [PATCH RFC v2 net-next 05/28] net/sched: act_api: introduce tc_lookup_action

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Date: Sat, 3 Jun 2023 09:14:53 -0400
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Marcelo Ricardo Leitner <mleitner@...hat.com>
Cc: netdev@...r.kernel.org, deb.chatterjee@...el.com, anjali.singhai@...el.com, 
	namrata.limaye@...el.com, tom@...anda.io, p4tc-discussions@...devconf.info, 
	Mahesh.Shirshyad@....com, Vipin.Jain@....com, tomasz.osinski@...el.com, 
	jiri@...nulli.us, xiyou.wangcong@...il.com, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, vladbu@...dia.com, 
	simon.horman@...igine.com, khalidm@...dia.com, toke@...hat.com
Subject: Re: [PATCH RFC v2 net-next 05/28] net/sched: act_api: introduce tc_lookup_action_byid()

On Fri, Jun 2, 2023 at 3:36 PM Marcelo Ricardo Leitner
<mleitner@...hat.com> wrote:
>
> On Wed, May 17, 2023 at 07:02:09AM -0400, Jamal Hadi Salim wrote:
> > +/* lookup by ID */
> > +struct tc_action_ops *tc_lookup_action_byid(struct net *net, u32 act_id)
> > +{
> > +     struct tcf_dyn_act_net *base_net;
> > +     struct tc_action_ops *a, *res = NULL;
> > +
> > +     if (!act_id)
> > +             return NULL;
> > +
> > +     read_lock(&act_mod_lock);
> > +
> > +     list_for_each_entry(a, &act_base, head) {
> > +             if (a->id == act_id) {
> > +                     if (try_module_get(a->owner)) {
> > +                             read_unlock(&act_mod_lock);
> > +                             return a;
> > +                     }
> > +                     break;
>
> It shouldn't call break here but instead already return NULL:
> if id matched, it cannot be present on the dyn list.
>
> Moreover, the search be optimized: now that TCA_ID_ is split between
> fixed and dynamic ranges (patch #3), it could jump directly into the
> right list. Control path performance is also important..



Sorry - didnt respond to this last part: We could use standard tc
actions in a P4 program and we prioritize looking at them first. This
helper is currently only needed for us - so you could argue that we
should only look TCA_ID_DYN onwards but it is useful to be more
generic and since this is a slow path it is not critical. Unless i
misunderstood what you said.

cheers,
jamal

> > +             }
> > +     }
> > +     read_unlock(&act_mod_lock);
> > +
> > +     read_lock(&base_net->act_mod_lock);
> > +
> > +     base_net = net_generic(net, dyn_act_net_id);
> > +     a = idr_find(&base_net->act_base, act_id);
> > +     if (a && try_module_get(a->owner))
> > +             res = a;
> > +
> > +     read_unlock(&base_net->act_mod_lock);
> > +
> > +     return res;
> > +}
> > +EXPORT_SYMBOL(tc_lookup_action_byid);
>