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 9425DC6FD1F for ; Sat, 25 Mar 2023 03:23:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231834AbjCYDXy (ORCPT ); Fri, 24 Mar 2023 23:23:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58154 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231572AbjCYDXv (ORCPT ); Fri, 24 Mar 2023 23:23:51 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8FFC1498F; Fri, 24 Mar 2023 20:23:49 -0700 (PDT) Received: from kwepemm600012.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Pk48j5wpfz17Ngh; Sat, 25 Mar 2023 11:20:37 +0800 (CST) Received: from [10.174.178.220] (10.174.178.220) by kwepemm600012.china.huawei.com (7.193.23.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Sat, 25 Mar 2023 11:23:47 +0800 Message-ID: Date: Sat, 25 Mar 2023 11:23:46 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH 0/5]scsi:scsi_debug: Add error injection for single device Content-Language: en-US To: , John Garry , "James E . J . Bottomley" , "Martin K . Petersen" , , CC: , References: <20230323115601.178494-1-haowenchao2@huawei.com> <750a4b24-6122-6faa-fed4-25e3167ea376@oracle.com> <164655df-0db3-0ec5-fb84-ff52204577e9@huawei.com> <5763743e-1923-d06e-04b7-19dfa0e8e2f4@interlog.com> From: "haowenchao (C)" In-Reply-To: <5763743e-1923-d06e-04b7-19dfa0e8e2f4@interlog.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.220] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemm600012.china.huawei.com (7.193.23.74) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/3/25 1:31, Douglas Gilbert wrote: > On 2023-03-23 23:42, haowenchao (C) wrote: >> On 2023/3/24 1:24, Douglas Gilbert wrote: >>> On 2023-03-23 12:25, John Garry wrote: >>>> On 23/03/2023 13:13, haowenchao (C) wrote: >>>>> On 2023/3/23 20:40, John Garry wrote: >>>>>> On 23/03/2023 11:55, Wenchao Hao wrote: >>>>>>> The original error injection mechanism was based on scsi_host which >>>>>>> could not inject fault for a single SCSI device. >>>>>>> >>>>>>> This patchset provides the ability to inject errors for a single >>>>>>> SCSI device. Now we supports inject timeout errors, queuecommand >>>>>>> errors, and hostbyte, driverbyte, statusbyte, and sense data for >>>>>>> specific SCSI Command. >>>>>> >>>>>> There is already a basic mechanism to generate errors - like timeouts - on "nth" command. Can you say why you want this new interface? What special scenarios are you trying to test/validate (which could not be achieved based on the current mechanism)? >>>>>> >>>>> >>>>> I am testing a new error handle policy which is based on single scsi_device >>>>> without set host to RECOVERY. So I need a method to generate errors for >>>>> single SCSI devices. >>>>> >>>>> While we can not generate errors for single device with current mechanism >>>>> because it is designed for host-wide error generation. >>>>> >>>>>> With this series we would have 2x methods to inject errors, which is less than ideal, and they seem to possibly conflict as well, e.g. I set timeout for nth command via current interface and then use the new interface to set timeout for some other cadence. What behavior to expect ...? >>>>> >>>>> I did not take this issue in consideration. I now assume the users would >>>>> not use these 2 methods at same time. >>>>> >>>>> What's more, I don not know where to write the usage of this newly added >>>>> interface, maybe we can explain these in doc? >>>> >>>> sysfs entries are described in Documentation/ABI, but please don't add elaborate programming interfaces in sysfs files (like in these patches) - a sysfs file should be just for reading or writing a single value >>> >>> Hi, >>> Maybe this link might help for scsi_debug documentation: >>>      https://doug-gilbert.github.io/scsi_debug.html >>> >>> And rather than sysfs for complicated, per (pseudo_ device >>> settings, perhaps we could think about a SCSI mechanism like >>> the "Unit Attention" mode page [0x0] which is vendor specific >>> and used by Seagate and WDC for this sort of thing. >>> A framework is already in the scsi_debug driver to change >>> some mode page settings: >>> >>> # sdparm /dev/sg0 >>>      /dev/sg0: Linux     scsi_debug        0191 >>> Read write error recovery mode page: >>>    AWRE          1  [cha: n, def:  1] >>>    ARRE          1  [cha: n, def:  1] >>>    PER           0  [cha: n, def:  0] >>> Caching (SBC) mode page: >>>    WCE           1  [cha: y, def:  1] >>>    RCD           0  [cha: n, def:  0] >>> Control mode page: >>>    SWP           0  [cha: n, def:  0] >>> Informational exceptions control mode page: >>>    EWASC         0  [cha: n, def:  0] >>>    DEXCPT        1  [cha: n, def:  1] >>>    MRIE          0  [cha: y, def:  0] >>> >>> As can be seen WCE and MRIE are changeable, so >>> >>> # sdparm --clear=WCE /dev/sg0 >>> # sdparm --get=WCE /dev/sg0 >>>      /dev/sg0: Linux     scsi_debug        0191 >>> WCE           0  [cha: y, def:  1] >>> >>> >>> Doug Gilbert >>> >>> >> >> Do you mean define scsi_debug's own format of mode page0(Vendor specific) >> which contains these error injection info, and set/get these parameters >> via sdparm? >> If so, do we need to modify the sdparm code for these changes? > > Not a problem. > >> I want to add more injections in scsi_debug to test the SCSI middle layer, >> for example, control return SUCCESS in scsi_debug_abort() or >> scsi_debug_device_reset(). >> >> These injections are more oriented to developers to trigger and observe >> the error handler of SCSI middle layer. >> >> We can extend other error injections conveniently via my interface, >> for example, add a new error code to add a new injection to control the >> return value of scsi_debug_abort(). >> >> If it's not recommended to add this interface in sysfs, what about proc? Like >> /proc/scsi/scsi, we can write "scsi remove-single-device h:c:t:l" to manage >> device. > > In the past, procfs has been used for this sort of thing > but the powers that be want to phase that usage out. > > debugfs, even though it is usually mounted under sysfs at > /sys/kernel/debug , does not seem to have the "one value > per variable" restriction. So debugfs or configfs > ( /sys/kernel/config ) might be better candidates. > See 'df -ahT' . > Define scsi_debug's own format of mode page0 seems too complex and we have to change the sdparm code. In order to make a better scalability, I prefer to add these interface via debugfs. Actually, I design the format of the "error interface" described in patch1 by referring to interfaces of ftrace. The new interfaces based on debugfs would look like following: /sys/kernel/debug/scsi_debug | +-- 0:0:0:1 | | | \-- error | \-- 0:0:0:2 | \-- error >>>>>> I'm not saying that I am a huge fan of the current inject mechanism, but at the very least you need to provide more justification for this series. >>>>>>>> >>>>>>> The first patch add an sysfs interface to add and inquiry single >>>>>>> device's error injection info; the second patch defined how to remove >>>>>>> an injection which has been added. The following 3 patches use the >>>>>>> injection info and generate the related error type. >>>>>>> >>>>>>> Wenchao Hao (5): >>>>>>>    scsi:scsi_debug: Add sysfs interface to manage scsi devices' error >>>>>>>      injection >>>>>>>    scsi:scsi_debug: Define grammar to remove added error injection >>>>>>>    scsi:scsi_debug: timeout command if the error is injected >>>>>>>    scsi:scsi_debug: Return failed value if the error is injected >>>>>>>    scsi:scsi_debug: set command's result and sense data if the error is >>>>>>>      injected >>>>>>> >>>>>>>   drivers/scsi/scsi_debug.c | 296 ++++++++++++++++++++++++++++++++++++++ >>>>>>>   1 file changed, 296 insertions(+) >>>>>>> >>>>>> >>>>>> >>>>> >>>> >>> >>> >> > >