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 2F899C197A0 for ; Thu, 16 Nov 2023 11:50:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230340AbjKPLuO (ORCPT ); Thu, 16 Nov 2023 06:50:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230160AbjKPLuN (ORCPT ); Thu, 16 Nov 2023 06:50:13 -0500 Received: from out30-118.freemail.mail.aliyun.com (out30-118.freemail.mail.aliyun.com [115.124.30.118]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CB094B0; Thu, 16 Nov 2023 03:50:08 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R271e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=alibuda@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0VwWMTyL_1700135405; Received: from 30.221.149.90(mailfrom:alibuda@linux.alibaba.com fp:SMTPD_---0VwWMTyL_1700135405) by smtp.aliyun-inc.com; Thu, 16 Nov 2023 19:50:06 +0800 Message-ID: Date: Thu, 16 Nov 2023 19:50:03 +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 v1] net/smc: avoid data corruption caused by decline Content-Language: en-US To: Wenjia Zhang , dust.li@linux.alibaba.com, kgraul@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 References: <1699436909-22767-1-git-send-email-alibuda@linux.alibaba.com> <20231113034457.GA121324@linux.alibaba.com> <17abf559-ec8b-47e9-b4e4-59adfbc6943b@linux.ibm.com> From: "D. Wythe" In-Reply-To: <17abf559-ec8b-47e9-b4e4-59adfbc6943b@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 11/15/23 10:06 PM, Wenjia Zhang wrote: > > > On 13.11.23 04:44, Dust Li wrote: >> On Wed, Nov 08, 2023 at 05:48:29PM +0800, 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, >>> 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 >>> --- >>> 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 abd2667..5b91f55 100644 >>> --- a/net/smc/af_smc.c >>> +++ b/net/smc/af_smc.c >>> @@ -599,7 +599,7 @@ static int smcr_clnt_conf_first_link(struct >>> smc_sock *smc) >>>     int rc; >>> >>>     /* receive CONFIRM LINK request from server over RoCE fabric */ >>> -    qentry = smc_llc_wait(link->lgr, NULL, SMC_LLC_WAIT_TIME, >>> +    qentry = smc_llc_wait(link->lgr, NULL, 2 * SMC_LLC_WAIT_TIME, >>>                   SMC_LLC_CONFIRM_LINK); >> >> It may be difficult for people to understand why LLC_WAIT_TIME is >> different, especially without any comments explaining its purpose. >> People are required to use git to find the reason, which I believe is >> not conducive to easy maintenance. >> >> Best regards, >> Dust >> >> > Good point! @D.Wythe, could you please try to add a simple commet to > explain it? > Also good to me, i will add comment to explain it. D. Wythe > Thanks, > Wenjia >> >>>     if (!qentry) { >>>         struct smc_clc_msg_decline dclc; >>> -- >>> 1.8.3.1