netdev - Re: [PATCH net-next v12 03/15] net/sched: act_api: Update tc_action

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Date: Thu, 29 Feb 2024 13:30:12 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, deb.chatterjee@...el.com, anjali.singhai@...el.com, 
	namrata.limaye@...el.com, tom@...anda.io, mleitner@...hat.com, 
	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, vladbu@...dia.com, horms@...nel.org, 
	khalidm@...dia.com, toke@...hat.com, daniel@...earbox.net, 
	victor@...atatu.com, pctammela@...atatu.com, bpf@...r.kernel.org
Subject: Re: [PATCH net-next v12 03/15] net/sched: act_api: Update
 tc_action_ops to account for P4 actions

On Thu, Feb 29, 2024 at 11:19 AM Paolo Abeni <pabeni@...hat.com> wrote:
>
> On Sun, 2024-02-25 at 11:54 -0500, Jamal Hadi Salim wrote:
> > The initialisation of P4TC action instances require access to a struct
> > p4tc_act (which appears in later patches) to help us to retrieve
> > information like the P4 action parameters etc. In order to retrieve
> > struct p4tc_act we need the pipeline name or id and the action name or id.
> > Also recall that P4TC action IDs are P4 and are net namespace specific and
> > not global like standard tc actions.
> > The init callback from tc_action_ops parameters had no way of
> > supplying us that information. To solve this issue, we decided to create a
> > new tc_action_ops callback (init_ops), that provies us with the
> > tc_action_ops  struct which then provides us with the pipeline and action
> > name.
>
> The new init ops looks a bit unfortunate. I *think* it would be better
> adding the new argument to the existing init op
>

Our initial goal was to avoid creating a much larger patch by changing
any other action's code and we observe that ->init() already has 8
params already ;-> And only dynamic actions need this extra extension.
If you still feel the change is needed, sure we can make that change.

> > In addition we add a new refcount to struct tc_action_ops called
> > dyn_ref, which accounts for how many action instances we have of a specific
> > action.
> >
> > Co-developed-by: Victor Nogueira <victor@...atatu.com>
> > Signed-off-by: Victor Nogueira <victor@...atatu.com>
> > Co-developed-by: Pedro Tammela <pctammela@...atatu.com>
> > Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
> > Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
> > Reviewed-by: Vlad Buslov <vladbu@...dia.com>
> > Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> > ---
> >  include/net/act_api.h |  6 ++++++
> >  net/sched/act_api.c   | 14 +++++++++++---
> >  2 files changed, 17 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/net/act_api.h b/include/net/act_api.h
> > index c839ff57c..69be5ed83 100644
> > --- a/include/net/act_api.h
> > +++ b/include/net/act_api.h
> > @@ -109,6 +109,7 @@ struct tc_action_ops {
> >       char    kind[ACTNAMSIZ];
> >       enum tca_id  id; /* identifier should match kind */
> >       unsigned int    net_id;
> > +     refcount_t p4_ref;
> >       size_t  size;
> >       struct module           *owner;
> >       int     (*act)(struct sk_buff *, const struct tc_action *,
> > @@ -120,6 +121,11 @@ struct tc_action_ops {
> >                       struct nlattr *est, struct tc_action **act,
> >                       struct tcf_proto *tp,
> >                       u32 flags, struct netlink_ext_ack *extack);
> > +     /* This should be merged with the original init action */
> > +     int     (*init_ops)(struct net *net, struct nlattr *nla,
> > +                         struct nlattr *est, struct tc_action **act,
> > +                        struct tcf_proto *tp, struct tc_action_ops *ops,
>
> shouldn't the 'ops' argument be 'const'?
>

As it is right now this would be hard to do because we carry around a
refcnt in that struct. We will think about it..


cheers,
jamal


> Thanks,
>
> Paolo
>