linux-kernel - Re: [PATCH net] net/smc: return the right falback reason when prefix checks fail

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Message-ID: <20231013011912.GS92403@linux.alibaba.com>
Date:   Fri, 13 Oct 2023 09:19:12 +0800
From:   Dust Li <dust.li@...ux.alibaba.com>
To:     Alexandra Winter <wintera@...ux.ibm.com>,
        Karsten Graul <kgraul@...ux.ibm.com>,
        Wenjia Zhang <wenjia@...ux.ibm.com>,
        Jan Karcher <jaka@...ux.ibm.com>,
        "D. Wythe" <alibuda@...ux.alibaba.com>,
        Tony Lu <tonylu@...ux.alibaba.com>,
        Wen Gu <guwen@...ux.alibaba.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net/smc: return the right falback reason when prefix
 checks fail

On Thu, Oct 12, 2023 at 03:05:20PM +0200, Alexandra Winter wrote:
>
>
>On 12.10.23 14:37, Dust Li wrote:
>> In the smc_listen_work(), if smc_listen_prfx_check() failed,
>> the real reason: SMC_CLC_DECL_DIFFPREFIX was dropped, and
>> SMC_CLC_DECL_NOSMCDEV was returned.
>> 
>> Althrough this is also kind of SMC_CLC_DECL_NOSMCDEV, but return
>> the real reason is much friendly for debugging.
>> 
>> Fixes: e49300a6bf62 ("net/smc: add listen processing for SMC-Rv2")
>> Signed-off-by: Dust Li <dust.li@...ux.alibaba.com>
>
>As you point out the current code is not really wrong. So I am not sure,
>whether this should be a fix for net, or rather a debug improvement for
>net-next.

To be honest, I was a bit conflicted which branch should this go for.
But after checking the code before e49300a6bf62 ("net/smc: add listen
processing for SMC-Rv2"), I discovered the previous behavior was to return
SMC_CLC_DECL_DIFFPREFIX. Therefor, I have decided it should be
considered a fix.

I should have memtioned this in the commit message.

Best regards,
Dust


>
>> ---
>>  net/smc/af_smc.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>> index bacdd971615e..21d4476b937b 100644
>> --- a/net/smc/af_smc.c
>> +++ b/net/smc/af_smc.c
>> @@ -2361,7 +2361,7 @@ static int smc_listen_find_device(struct smc_sock *new_smc,
>>  		smc_find_ism_store_rc(rc, ini);
>>  		return (!rc) ? 0 : ini->rc;
>>  	}
>> -	return SMC_CLC_DECL_NOSMCDEV;
>> +	return prfx_rc;
>>  }
>>  
>>  /* listen worker: finish RDMA setup */
>
>For the code change:
>Reviewed-by: Alexandra Winter <wintera@...ux.ibm.com>