linux-kernel - Re: [saeed:net-next 154/185] net/smc/smc_sysctl.h:23:16: warning: no previous prototype for 'smc_sysctl_net

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Message-ID: <20220309033008.GH35207@linux.alibaba.com>
Date:   Wed, 9 Mar 2022 11:30:08 +0800
From:   "dust.li" <dust.li@...ux.alibaba.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     kernel test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: [saeed:net-next 154/185] net/smc/smc_sysctl.h:23:16: warning: no
 previous prototype for 'smc_sysctl_net_init'

On Mon, Mar 07, 2022 at 09:25:20PM -0800, Jakub Kicinski wrote:
>On Tue, 8 Mar 2022 13:16:55 +0800 dust.li wrote:
>> >vim +/smc_sysctl_net_init +23 net/smc/smc_sysctl.h
>> >
>> >    22	  
>> >  > 23	int __net_init smc_sysctl_net_init(struct net *net)  
>> >    24	{
>> >    25		net->smc.sysctl_autocorking_size = SMC_AUTOCORKING_DEFAULT_SIZE;
>> >    26		return 0;
>> >    27	}
>> >    28	  
>> >  > 29	void __net_exit smc_sysctl_net_exit(struct net *net) { }  
>> >    30	  
>> 
>> Hi Jakub:
>> 
>> Sorry to bother again on this !
>> Looks like we still need to add 'static inline' or add an extra
>> declaration for these 2 functions if we want to get rid of these warnings.
>> What do you think ?
>
>Sorry my comment was pretty unclear an unnecessary.
>
>I meant that you don't need the __net_init annotation, it still 
>needs to be a static inline. So this is what I meant:
>
>diff --git a/net/smc/smc_sysctl.h b/net/smc/smc_sysctl.h
>index 1d554300604d..0becc11bd2f4 100644
>--- a/net/smc/smc_sysctl.h
>+++ b/net/smc/smc_sysctl.h
>@@ -20,13 +20,13 @@ void __net_exit smc_sysctl_net_exit(struct net *net);
> 
> #else
> 
>-int __net_init smc_sysctl_net_init(struct net *net)
>+static inline int smc_sysctl_net_init(struct net *net)
> {
>        net->smc.sysctl_autocorking_size = SMC_AUTOCORKING_DEFAULT_SIZE;
>        return 0;
> }
> 
>-void __net_exit smc_sysctl_net_exit(struct net *net) { }
>+static inline void smc_sysctl_net_exit(struct net *net) { }
> 
> #endif /* CONFIG_SYSCTL */
>
>
>
>But really it does not matter if the __net_init / exit is there, 
>so this works too:

Another small comment:

When re-compile with the W=1, I found '__net_exit' has noinline
annotation when CONFIG_NET_NS not set:

 #define __net_exit      __ref
 #define __ref           __section(".ref.text") noinline

If '__net_exit' is used together with 'static inline', the compiler
would give another warning:
 net/smc/smc_sysctl.h:29:58: warning: ignoring attribute ‘gnu_inline’
 because it conflicts with attribute ‘noinline’ [-Wattributes]
    29 | static inline void __net_exit smc_sysctl_net_exit(struct net
    *net) { }

So I think your first version would be good.

Thanks.

>
>diff --git a/net/smc/smc_sysctl.h b/net/smc/smc_sysctl.h
>index 1d554300604d..6979e7173669 100644
>--- a/net/smc/smc_sysctl.h
>+++ b/net/smc/smc_sysctl.h
>@@ -20,13 +20,13 @@ void __net_exit smc_sysctl_net_exit(struct net *net);
> 
> #else
> 
>-int __net_init smc_sysctl_net_init(struct net *net)
>+static inline int __net_init smc_sysctl_net_init(struct net *net)
> {
>        net->smc.sysctl_autocorking_size = SMC_AUTOCORKING_DEFAULT_SIZE;
>        return 0;
> }
> 
>-void __net_exit smc_sysctl_net_exit(struct net *net) { }
>+static inline void __net_exit smc_sysctl_net_exit(struct net *net) { }
> 
> #endif /* CONFIG_SYSCTL */
>