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 4C7B7C4167B for ; Mon, 13 Nov 2023 10:58:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229595AbjKMK6H (ORCPT ); Mon, 13 Nov 2023 05:58:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229470AbjKMK6G (ORCPT ); Mon, 13 Nov 2023 05:58:06 -0500 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39A87CB; Mon, 13 Nov 2023 02:58:03 -0800 (PST) Received: from pps.filterd (m0353728.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3ADAMInx022325; Mon, 13 Nov 2023 10:57:54 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=mO9wHnLHdy2du+X37iMKlBJstawyD+g6Bim8ZoWChSo=; b=CBgae9CnrymhtSKaTgjF+8R6vm+bywT12Nga2x2cDXI7ktWtqFz1h1xJk4t1Qs4/lAHR 5ZQ4kkuzky2v2o+cGVu5PpItlOhc2bN6zBbnqqswr35IaUSsQJ/wQL8oHG/D1k8TAw+F FSUYq/L+kHPoU1OUkwS0AuxN8OGQ3VM9R64RAbkqkTx/oq9jeGWRncsxh1xZ1aiu0Ss5 tOrnZMaaWGJkgCLbQe13qZq870PEqcZzJsXS2CY8eIquCVWMZ0uA1MWdUn9l8Gf86VVK vfXO8nBMI3PI/f+2wGOcuwGtCekIHDpYyDt2zaO6cif3YbAJe/8CBnjqeUrZtpWAWrX4 dg== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3ubj038pw8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Nov 2023 10:57:54 +0000 Received: from m0353728.ppops.net (m0353728.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 3ADAsmxu021993; Mon, 13 Nov 2023 10:57:54 GMT Received: from ppma11.dal12v.mail.ibm.com (db.9e.1632.ip4.static.sl-reverse.com [50.22.158.219]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3ubj038pw1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Nov 2023 10:57:54 +0000 Received: from pps.filterd (ppma11.dal12v.mail.ibm.com [127.0.0.1]) by ppma11.dal12v.mail.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 3ADA41cE015483; Mon, 13 Nov 2023 10:57:53 GMT Received: from smtprelay03.dal12v.mail.ibm.com ([172.16.1.5]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 3uapn17xax-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Nov 2023 10:57:53 +0000 Received: from smtpav03.wdc07v.mail.ibm.com (smtpav03.wdc07v.mail.ibm.com [10.39.53.230]) by smtprelay03.dal12v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 3ADAvqJq60490032 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Nov 2023 10:57:52 GMT Received: from smtpav03.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1DB205805D; Mon, 13 Nov 2023 10:57:52 +0000 (GMT) Received: from smtpav03.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 640965805C; Mon, 13 Nov 2023 10:57:50 +0000 (GMT) Received: from [9.171.9.165] (unknown [9.171.9.165]) by smtpav03.wdc07v.mail.ibm.com (Postfix) with ESMTP; Mon, 13 Nov 2023 10:57:50 +0000 (GMT) Message-ID: Date: Mon, 13 Nov 2023 11:57:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v1] net/smc: avoid data corruption caused by decline Content-Language: en-GB To: "D. Wythe" , 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> <05c29431-c941-45d1-8e14-0527accc3993@linux.ibm.com> <3f3080e2-cb2c-16f4-02b1-ca17394d2813@linux.alibaba.com> From: Wenjia Zhang In-Reply-To: <3f3080e2-cb2c-16f4-02b1-ca17394d2813@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 8xuwEe4VKcs5traCjvrjp9rPpvbJMH2D X-Proofpoint-ORIG-GUID: sjbnbvJX7Re9-DiFR1uJwPSf-IPzJv7t X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-12_24,2023-11-09_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 malwarescore=0 spamscore=0 phishscore=0 suspectscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 mlxscore=0 clxscore=1015 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311130090 Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 13.11.23 03:50, D. Wythe wrote: > > > On 11/10/23 10:51 AM, D. Wythe wrote: >> >> >> On 11/8/23 9:00 PM, Wenjia Zhang wrote: >>> >>> >>> On 08.11.23 10:48, 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); >>>>       if (!qentry) { >>>>           struct smc_clc_msg_decline dclc; >>> I'm wondering if the double time (if sufficient) of timeout could be >>> for waiting for CLC_DECLINE on the client's side. i.e. >>> >> >> It depends. We can indeed introduce a sysctl to allow server to >> manager their Confirm Link timeout, >> but if there will be protocol updates, this introduction will no >> longer be necessary, and we will >> have to maintain it continuously. >> no, I don't think, either, that we need a sysctl for that. >> I believe the core of the solution is to ensure that decline messages >> never cross or collide. Increasing >> the client's timeout by twice as much as the server's timeout can >> temporarily solve this problem. I have no objection with that, but my question is why you don't increase the timeout waiting for CLC_DECLINE instead of waiting LLC_Confirm_Link? Shouldn't they have the same effect? >> If Jerry's proposed protocol updates are too complex or if there won't >> be any future protocol updates, >> it's still not late to let server manager their Confirm Link timeout >> then. >> >> Best wishes, >> D. Wythe >> > > FYI: > > It seems that my email was not successfully delivered due to some > reasons. Sorry > for that. > > D. Wythe > > >>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c >>> index 35ddebae8894..9b1feef1013d 100644 >>> --- a/net/smc/af_smc.c >>> +++ b/net/smc/af_smc.c >>> @@ -605,7 +605,7 @@ static int smcr_clnt_conf_first_link(struct >>> smc_sock *smc) >>>                 struct smc_clc_msg_decline dclc; >>> >>>                 rc = smc_clc_wait_msg(smc, &dclc, sizeof(dclc), >>> -                                     SMC_CLC_DECLINE, >>> CLC_WAIT_TIME_SHORT); >>> +                                     SMC_CLC_DECLINE, 2 * >>> CLC_WAIT_TIME_SHORT); >>>                 return rc == -EAGAIN ? SMC_CLC_DECL_TIMEOUT_CL : rc; >>>         } >>>         smc_llc_save_peer_uid(qentry); >>> >>> Because the purpose is to let the server have the control to deline. >> >