From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2AE0BC072A2 for ; Fri, 17 Nov 2023 06:53:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229927AbjKQGxM (ORCPT ); Fri, 17 Nov 2023 01:53:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229436AbjKQGxL (ORCPT ); Fri, 17 Nov 2023 01:53:11 -0500 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3AE04192; Thu, 16 Nov 2023 22:53:07 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045170;MF=alibuda@linux.alibaba.com;NM=1;PH=DS;RN=13;SR=0;TI=SMTPD_---0VwYgl8u_1700203983; Received: from 30.221.148.229(mailfrom:alibuda@linux.alibaba.com fp:SMTPD_---0VwYgl8u_1700203983) by smtp.aliyun-inc.com; Fri, 17 Nov 2023 14:53:05 +0800 Message-ID: <44551f7f-5890-2141-cf90-9d7095d55502@linux.alibaba.com> Date: Fri, 17 Nov 2023 14:53:02 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH net v2] net/smc: avoid data corruption caused by decline Content-Language: en-US To: Wen Gu , kgraul@linux.ibm.com, wenjia@linux.ibm.com, jaka@linux.ibm.com, wintera@linux.ibm.com Cc: kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org, tonylu@linux.alibaba.com, pabeni@redhat.com, edumazet@google.com References: <1700197181-83136-1-git-send-email-alibuda@linux.alibaba.com> From: "D. Wythe" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 11/17/23 2:47 PM, Wen Gu wrote: > > > On 2023/11/17 12:59, D. Wythe wrote: > >> From: "D. Wythe" >> >> We found a data corruption issue during testing of SMC-R on Redis >> applications. >> >> The benchmark has a low probability of reporting a strange error as >> shown below. >> >> "Error: Protocol error, got "\xe2" as reply type byte" >> >> Finally, we found that the retrieved error data was as follows: >> >> 0xE2 0xD4 0xC3 0xD9 0x04 0x00 0x2C 0x20 0xA6 0x56 0x00 0x16 0x3E 0x0C >> 0xCB 0x04 0x02 0x01 0x00 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x00 0x00 >> 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xE2 >> >> It is quite obvious that this is a SMC DECLINE message, which means that >> the applications received SMC protocol message. >> We found that this was caused by the following situations: >> >> client            server >>        proposal >>     -------------> >>        accept >>     <------------- >>        confirm >>     -------------> >> wait confirm >> >>      failed llc confirm >>         x------ >> (after 2s)timeout >>             wait rsp >> >> wait decline >> >> (after 1s) timeout >>             (after 2s) timeout >>         decline >>     --------------> >>         decline >>     <-------------- >> >> As a result, a decline message was sent in the implementation, and this >> message was read from TCP by the already-fallback connection. >> >> This patch double the client timeout as 2x of the server value, > > Is the client's timeout doubled? > > From the code below, it is server's timeout that has been doubled. > Forget to fix description, i'll fix that in next revision. >> With this simple change, the Decline messages should never cross or >> collide (during Confirm link timeout). >> >> This issue requires an immediate solution, since the protocol updates >> involve a more long-term solution. >> >> Fixes: 0fb0b02bd6fd ("net/smc: adapt SMC client code to use the LLC >> flow") >> Signed-off-by: D. Wythe >> --- >>   include/net/netns/smc.h |  2 ++ >>   net/smc/af_smc.c        |  3 ++- >>   net/smc/smc_sysctl.c    | 12 ++++++++++++ >>   3 files changed, 16 insertions(+), 1 deletion(-) >> >> diff --git a/include/net/netns/smc.h b/include/net/netns/smc.h >> index 582212a..5198896 100644 >> --- a/include/net/netns/smc.h >> +++ b/include/net/netns/smc.h >> @@ -22,5 +22,7 @@ struct netns_smc { >>       int                sysctl_smcr_testlink_time; >>       int                sysctl_wmem; >>       int                sysctl_rmem; >> +    /* server's Confirm Link timeout in seconds */ >> +    int                sysctl_smcr_srv_confirm_link_timeout; >>   }; >>   #endif >> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c >> index abd2667..b86ad30 100644 >> --- a/net/smc/af_smc.c >> +++ b/net/smc/af_smc.c >> @@ -1870,7 +1870,8 @@ static int smcr_serv_conf_first_link(struct >> smc_sock *smc) >>           return SMC_CLC_DECL_TIMEOUT_CL; >>         /* receive CONFIRM LINK response from client over the RoCE >> fabric */ >> -    qentry = smc_llc_wait(link->lgr, link, SMC_LLC_WAIT_TIME, >> +    qentry = smc_llc_wait(link->lgr, link, >> + sock_net(&smc->sk)->smc.sysctl_smcr_srv_confirm_link_timeout, >>                     SMC_LLC_CONFIRM_LINK); >>       if (!qentry) { >>           struct smc_clc_msg_decline dclc; >> diff --git a/net/smc/smc_sysctl.c b/net/smc/smc_sysctl.c >> index 5cbc18c..919f3f7 100644 >> --- a/net/smc/smc_sysctl.c >> +++ b/net/smc/smc_sysctl.c >> @@ -51,6 +51,13 @@ >>           .proc_handler    = proc_dointvec_jiffies, >>       }, >>       { >> +        .procname    = "smcr_srv_confirm_link_timeout", >> +        .data        = >> &init_net.smc.sysctl_smcr_srv_confirm_link_timeout, >> +        .maxlen        = sizeof(int), >> +        .mode        = 0644, >> +        .proc_handler    = proc_dointvec_jiffies, >> +    }, >> +    { >>           .procname    = "wmem", >>           .data        = &init_net.smc.sysctl_wmem, >>           .maxlen        = sizeof(int), >> @@ -95,6 +102,11 @@ int __net_init smc_sysctl_net_init(struct net *net) >>       net->smc.sysctl_autocorking_size = SMC_AUTOCORKING_DEFAULT_SIZE; >>       net->smc.sysctl_smcr_buf_type = SMCR_PHYS_CONT_BUFS; >>       net->smc.sysctl_smcr_testlink_time = >> SMC_LLC_TESTLINK_DEFAULT_TIME; >> +    /* Increasing the server's timeout by twice as much as the client's >> +     * timeout by default can temporarily avoid decline messages of >> +     * both side been crossed or collided. > > 'both sides' or maybe better for > > '..avoid decline messages of both sides crossing or colliding.' > > Look nice. I'll adopt that. > > Thanks, > Wen Gu > >> +     */ >> +    net->smc.sysctl_smcr_srv_confirm_link_timeout = 2 * >> SMC_LLC_WAIT_TIME; >>       WRITE_ONCE(net->smc.sysctl_wmem, net_smc_wmem_init); >>       WRITE_ONCE(net->smc.sysctl_rmem, net_smc_rmem_init);