netdev - Re: [PATCH net-next 1/6] net/smc: support smc release version negotiation in clc handshake

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Date: Thu, 17 Aug 2023 11:18:47 +0800
From: Guangguan Wang <guangguan.wang@...ux.alibaba.com>
To: Jan Karcher <jaka@...ux.ibm.com>, wenjia@...ux.ibm.com,
 kgraul@...ux.ibm.com, tonylu@...ux.alibaba.com, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com
Cc: horms@...nel.org, alibuda@...ux.alibaba.com, guwen@...ux.alibaba.com,
 linux-s390@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/6] net/smc: support smc release version
 negotiation in clc handshake



On 2023/8/16 22:14, Jan Karcher wrote:
> 
> 
> On 16/08/2023 10:33, Guangguan Wang wrote:
>> Support smc release version negotiation in clc handshake based on
>> SMC v2, where no negotiation process for different releases, but
>> for different versions. The latest smc release version was updated
>> to v2.1. And currently there are two release versions of SMCv2, v2.0
>> and v2.1. In the release version negotiation, client sends the preferred
>> release version by CLC Proposal Message, server makes decision for which
>> release version to use based on the client preferred release version and
>> self-supported release version (here choose the minimum release version
>> of the client preferred and server latest supported), then the decision
>> returns to client by CLC Accept Message. Client confirms the decision by
>> CLC Confirm Message.
>>
>> Client                                    Server
>>        Proposal(preferred release version)
>>       ------------------------------------>
>>
>>        Accept(accpeted release version)
>>   min(client preferred, server latest supported)
>>       <------------------------------------
>>
>>        Confirm(accpeted release version)
>>       ------------------------------------>
>>
>> Signed-off-by: Guangguan Wang <guangguan.wang@...ux.alibaba.com>
>> Reviewed-by: Tony Lu <tonylu@...ux.alibaba.com>
>> ---
>>   net/smc/af_smc.c   | 18 ++++++++++++++++--
>>   net/smc/smc.h      |  5 ++++-
>>   net/smc/smc_clc.c  | 14 +++++++-------
>>   net/smc/smc_clc.h  | 23 ++++++++++++++++++++++-
>>   net/smc/smc_core.h |  1 +
>>   5 files changed, 50 insertions(+), 11 deletions(-)
>>
>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>> index a7f887d91d89..97265691bc95 100644
>> --- a/net/smc/af_smc.c
>> +++ b/net/smc/af_smc.c
>> @@ -1187,6 +1187,9 @@ static int smc_connect_rdma_v2_prepare(struct smc_sock *smc,
>>               return SMC_CLC_DECL_NOINDIRECT;
>>           }
>>       }
>> +
>> +    ini->release_nr = fce->release;
>> +
> 
> why would we do this and vvvvv
>>       return 0;
>>   }
>>   @@ -1355,6 +1358,13 @@ static int smc_connect_ism(struct smc_sock *smc,
>>           struct smc_clc_msg_accept_confirm_v2 *aclc_v2 =
>>               (struct smc_clc_msg_accept_confirm_v2 *)aclc;
>>   +        if (ini->first_contact_peer) {
>> +            struct smc_clc_first_contact_ext *fce =
>> +                smc_get_clc_first_contact_ext(aclc_v2, true);
>> +
>> +            ini->release_nr = fce->release;
>> +        }
>> +
> 
> this two times?
> Can't we put this together into __smc_connect where those functions get called (via smc_connect_rdma and smc_connect_ism)?
> 
> Please provide reasoning, it might be that i oversaw the reasoning behind this duplication.
> 
ini->release_nr is assigned only when doing first connect, thus this depends on the value test of 
ini->first_contact_peer. I have to follow the ini->first_contact_peer code logic, which may also
make us wonder that why not put ini->first_contact_peer together into __smc_connect.

Indeed, both of ini->first_contact_peer and ini->release_nr can put together into __smc_connect.
But I think it is better to start a new patch series to refactor those code, not in v2.1 features.


> Also note: Even if there is a reason to set this information seperate for SMC-D and SMC-R think about using your very neat helper function (smc_get_clc_first_contact_ext) in smc_connect_rdma_v2_prepare as well.
> 

OK, I will replace the code to smc_get_clc_first_contact_ext.

Thanks,
Guangguan Wang