netdev - Re: [PATCH net] net/sched: cls_api: Move call to tcf_exts_miss_cookie_base

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Date:   Sat, 25 Feb 2023 14:15:27 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, paulb@...dia.com, marcelo.leitner@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net/sched: cls_api: Move call to
 tcf_exts_miss_cookie_base_destroy()

On Sat, Feb 25, 2023 at 05:08:17PM +0100, Simon Horman wrote:
> On Fri, Feb 24, 2023 at 11:18:49AM -0700, Nathan Chancellor wrote:
> > When CONFIG_NET_CLS_ACT is disabled:
> > 
> >   ../net/sched/cls_api.c:141:13: warning: 'tcf_exts_miss_cookie_base_destroy' defined but not used [-Wunused-function]
> >     141 | static void tcf_exts_miss_cookie_base_destroy(struct tcf_exts *exts)
> >         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 
> > Due to the way the code is structured, it is possible for a definition
> > of tcf_exts_miss_cookie_base_destroy() to be present without actually
> > being used. Its single callsite is in an '#ifdef CONFIG_NET_CLS_ACT'
> > block but a definition will always be present in the file. The version
> > of tcf_exts_miss_cookie_base_destroy() that actually does something
> > depends on CONFIG_NET_TC_SKB_EXT, so the stub function is used in both
> > CONFIG_NET_CLS_ACT=n and CONFIG_NET_CLS_ACT=y + CONFIG_NET_TC_SKB_EXT=n
> > configurations.
> > 
> > Move the call to tcf_exts_miss_cookie_base_destroy() in
> > tcf_exts_destroy() out of the '#ifdef CONFIG_NET_CLS_ACT', so that it
> > always appears used to the compiler, while not changing any behavior
> > with any of the various configuration combinations.
> > 
> > Fixes: 80cd22c35c90 ("net/sched: cls_api: Support hardware miss to tc action")
> > Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> 
> Thanks Nathan,
> 
> I think the #ifdefs in this file could do with some work.

Yes, it is definitely an eye sore. I thought about cleaning it up but it
felt like net-next material to me, plus I have no other interest in this
code other than making the warning in my builds go away, if I am being
honest :)

> But as a fix this looks good to me.
> 
> Reviewed-by: Simon Horman <simon.horman@...igine.com>

Thanks for the quick review!

Cheers,
Nathan