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 37212C6FD1C for ; Thu, 23 Mar 2023 17:25:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231965AbjCWRZM (ORCPT ); Thu, 23 Mar 2023 13:25:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33048 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229508AbjCWRY4 (ORCPT ); Thu, 23 Mar 2023 13:24:56 -0400 Received: from mp-relay-02.fibernetics.ca (mp-relay-02.fibernetics.ca [208.85.217.137]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73F552686C; Thu, 23 Mar 2023 10:24:52 -0700 (PDT) Received: from mailpool-fe-02.fibernetics.ca (mailpool-fe-02.fibernetics.ca [208.85.217.145]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mp-relay-02.fibernetics.ca (Postfix) with ESMTPS id 8D76675C90; Thu, 23 Mar 2023 17:24:50 +0000 (UTC) Received: from localhost (mailpool-mx-01.fibernetics.ca [208.85.217.140]) by mailpool-fe-02.fibernetics.ca (Postfix) with ESMTP id 733B060AE0; Thu, 23 Mar 2023 17:24:50 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at Received: from mailpool-fe-02.fibernetics.ca ([208.85.217.145]) by localhost (mail-mx-01.fibernetics.ca [208.85.217.140]) (amavisd-new, port 10024) with ESMTP id X4If3C_OIL3F; Thu, 23 Mar 2023 17:24:50 +0000 (UTC) Received: from [192.168.48.17] (host-184-164-23-94.dyn.295.ca [184.164.23.94]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: dgilbert@interlog.com) by mail.ca.inter.net (Postfix) with ESMTPSA id 834B460ADC; Thu, 23 Mar 2023 17:24:49 +0000 (UTC) Message-ID: Date: Thu, 23 Mar 2023 13:24:48 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Reply-To: dgilbert@interlog.com Subject: Re: [PATCH 0/5]scsi:scsi_debug: Add error injection for single device Content-Language: en-CA To: John Garry , "haowenchao (C)" , "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Cc: linfeilong@huawei.com, louhongxiang@huawei.com References: <20230323115601.178494-1-haowenchao2@huawei.com> <750a4b24-6122-6faa-fed4-25e3167ea376@oracle.com> From: Douglas Gilbert In-Reply-To: <750a4b24-6122-6faa-fed4-25e3167ea376@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org 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 >>> 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(+) >>>> >>> >>> >> >