netdev - Re: [PATCH RFC net-next 3/4] net/sched: act_api: stop loop over ops array on NULL in tcf_action

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Date: Tue, 28 Nov 2023 11:11:15 -0800
From: Marcelo Ricardo Leitner <mleitner@...hat.com>
To: Pedro Tammela <pctammela@...atatu.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, jhs@...atatu.com, 
	xiyou.wangcong@...il.com, jiri@...nulli.us, vladbu@...dia.com
Subject: Re: [PATCH RFC net-next 3/4] net/sched: act_api: stop loop over ops
 array on NULL in tcf_action_init

On Tue, Nov 28, 2023 at 01:06:30PM -0300, Pedro Tammela wrote:
> @@ -1510,10 +1510,8 @@ int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
>  err:
>  	tcf_action_destroy(actions, flags & TCA_ACT_FLAGS_BIND);
>  err_mod:
> -	for (i = 0; i < TCA_ACT_MAX_PRIO; i++) {
> -		if (ops[i])
> -			module_put(ops[i]->owner);
> -	}
> +	for (i = 0; i < TCA_ACT_MAX_PRIO && ops[i]; i++)
> +		module_put(ops[i]->owner);
>  	return err;

I was going to say:
Maybe it's time for a helper macro for this.

$ git grep TCA_ACT_MAX_PRIO
include/net/pkt_cls.h:  for (i = 0; i < TCA_ACT_MAX_PRIO && ((a) =
(exts)->actions[i]); i++)
include/net/pkt_cls.h:  for (i = 0; i < TCA_ACT_MAX_PRIO && ((a) =
actions[i]); i++)
...
net/sched/act_api.c:    for (i = 0; i < TCA_ACT_MAX_PRIO && actions[i]; i++) {
net/sched/act_api.c:    for (i = 0; i < TCA_ACT_MAX_PRIO; i++) {
net/sched/act_api.c:    for (i = 0; i < TCA_ACT_MAX_PRIO && actions[i]; i++) {
net/sched/act_api.c:    for (i = 0; i < TCA_ACT_MAX_PRIO; i++) {
...
net/sched/act_api.c:    for (i = 1; i <= TCA_ACT_MAX_PRIO && tb[i]; i++) {
net/sched/act_api.c:    for (i = 1; i <= TCA_ACT_MAX_PRIO && tb[i]; i++) {
net/sched/act_api.c:    for (i = 0; i < TCA_ACT_MAX_PRIO; i++) {
net/sched/act_api.c:    for (i = 0; i < TCA_ACT_MAX_PRIO && actions[i]; i++) {
...

But then, that's exactly what the first 2 hits are :)
So AFAICT this loop can be written as:

struct struct tc_action_ops *op;
tcf_act_for_each_action(i, op, ops)
	module_put(op->owner);

Thoughts? It would be iterating over struct tc_action_ops and not
tc_action, as in tcf_act_for_each_action() (which is the only user of
this macro today), but that seems okay.

  Marcelo