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 X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF8C4C433E0 for ; Mon, 10 Aug 2020 12:03:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC9B22070B for ; Mon, 10 Aug 2020 12:03:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726586AbgHJMD5 (ORCPT ); Mon, 10 Aug 2020 08:03:57 -0400 Received: from comms.puri.sm ([159.203.221.185]:46476 "EHLO comms.puri.sm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726141AbgHJMD4 (ORCPT ); Mon, 10 Aug 2020 08:03:56 -0400 Received: from localhost (localhost [127.0.0.1]) by comms.puri.sm (Postfix) with ESMTP id 00EACDF67F; Mon, 10 Aug 2020 05:03:23 -0700 (PDT) Received: from comms.puri.sm ([127.0.0.1]) by localhost (comms.puri.sm [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OT2W_FCK0rVQ; Mon, 10 Aug 2020 05:03:22 -0700 (PDT) Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release To: Alan Stern Cc: James Bottomley , Bart Van Assche , Can Guo , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@puri.sm References: <20200729182515.GB1580638@rowland.harvard.edu> <1596047349.4356.84.camel@HansenPartnership.com> <20200730151030.GB6332@rowland.harvard.edu> <9b80ca7c-39f8-e52d-2535-8b0baf93c7d1@puri.sm> <425990b3-4b0b-4dcf-24dc-4e7e60d5869d@puri.sm> <20200807143002.GE226516@rowland.harvard.edu> <20200808150542.GB256751@rowland.harvard.edu> <20200809152643.GA277165@rowland.harvard.edu> From: Martin Kepplinger Autocrypt: addr=martin.kepplinger@puri.sm; keydata= mQINBFULfZABEADRxJqDOYAHfrp1w8Egcv88qoru37k1x0Ugy8S6qYtKLAAt7boZW+q5gPv3 Sj2KjfkWA7gotXpASN21OIfE/puKGwhDLAySY1DGNMQ0gIVakUO0ji5GJPjeB9JlmN5hbA87 Si9k3yKQQfv7Cf9Lr1iZaV4A4yjLP/JQMImaCVdC5KyqJ98Luwci1GbsLIGX3EEjfg1+MceO dnJTKZpBAKd1J7S2Ib3dRwvALdiD7zqMGqkw5xrtwasatS7pc6o/BFgA9GxbeIzKmvW/hc3Q amS/sB12BojyzdUJ3TnIoAqvwKTGcv5VYo2Z+3FV+/MJVXPo8cj2vmfxQx1WG4n6X0pK4X8A BkCKw2N/evMZblNqAzzGVtoJvqQYkzQ20Fm+d3wFl6lS1db4MB+kU13G8kEIE22Q3i6kx4NA N49FLlPeDabGfJUyDaZp5pmKdcd7/FIGH/HjShjx7g+LKSwWNMkDygr4WARAP4h8zYDZuNqe ofPvMLqJxHeexBPIGF/+OwMyTvM7otP5ODuFmq6OqjNPf1irJmkiFv3yEa+Ip0vZzwl4XvrZ U0IKjSy2rbRLg22NsJT0XVZJbutIXYSvIHGqSxzzfiOOLnRjR++fbeEoVlRJ4NZHDKCh3pJv LNd+j03jXr4Rm058YLgO7164yr7FhMZniBJw6z648rk8/8gGPQARAQABtC1NYXJ0aW4gS2Vw cGxpbmdlciA8bWFydGluLmtlcHBsaW5nZXJAcHVyaS5zbT6JAk4EEwEIADgWIQTyCCuID55C OTRobj9QA5jfWrOH0wUCXPSlkwIbAwULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRBQA5jf 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Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09.08.20 17:26, Alan Stern wrote: > On Sun, Aug 09, 2020 at 11:20:22AM +0200, Martin Kepplinger wrote: >> Hey Alan, I'm really glad for that, I suspected some of this but I have >> little experience in scsi/block layers, so that is super helpful. >> >> I'd appreciate an opinion on the below workaround that *seems* to work >> now (let's see, I had thought so before :) >> >> Whether or not this helps to find a real solution, let's see. But >> integration of such a flag in the error handling paths is what's >> interesting for now: >> >> >> --- a/drivers/scsi/scsi_error.c >> +++ b/drivers/scsi/scsi_error.c >> @@ -565,6 +565,17 @@ int scsi_check_sense(struct scsi_cmnd *scmd) >> return NEEDS_RETRY; >> } >> } >> + if (scmd->device->expecting_media_change) { >> + if (sshdr.asc == 0x28 && sshdr.ascq == 0x00) { >> + /* clear expecting_media_change in >> + * scsi_noretry_cmd() because we need >> + * to override possible "failfast" overrides >> + * that block readahead can cause. >> + */ >> + return NEEDS_RETRY; > > This is a somewhat fragile approach. You don't know for certain that > scsi_noretry_cmd will be called. Also, scsi_noretry_cmd can be called > from other places. > > It would be better to clear the expecting_media_change flag just before > returning from scsi_decide_disposition. That way its use is localized > to one routine, not spread out between two. > > Alan Stern > Hi Alan, maybe you're right. I initially just thought that I'd allow for specific error codes in scsi_noretry_cmd() to return non-NULL (BUS_BUSY, PARITY, ERROR) despite having the flag set. The below version works equally fine for me but I'm not sure if it's actually more safe. James, when exposing a new writable sysfs option like "suspend_no_media_change"(?) that drivers can check before setting the new "expecting_media_change" flag (during resume), would this addition make sense to you? thanks, martin --- a/drivers/scsi/scsi_error.c +++ b/drivers/scsi/scsi_error.c @@ -565,6 +565,18 @@ int scsi_check_sense(struct scsi_cmnd *scmd) return NEEDS_RETRY; } } + if (scmd->device->expecting_media_change) { + if (sshdr.asc == 0x28 && sshdr.ascq == 0x00) { + /* + * clear the expecting_media_change in + * scsi_decide_disposition() because we + * need to catch possible "fail fast" overrides + * that block readahead can cause. + */ + return NEEDS_RETRY; + } + } + /* * we might also expect a cc/ua if another LUN on the target * reported a UA with an ASC/ASCQ of 3F 0E - @@ -1944,9 +1956,19 @@ int scsi_decide_disposition(struct scsi_cmnd *scmd) * the request was not marked fast fail. Note that above, * even if the request is marked fast fail, we still requeue * for queue congestion conditions (QUEUE_FULL or BUSY) */ - if ((++scmd->retries) <= scmd->allowed - && !scsi_noretry_cmd(scmd)) { - return NEEDS_RETRY; + if ((++scmd->retries) <= scmd->allowed) { + /* + * but scsi_noretry_cmd() cannot override the + * expecting_media_change flag. + */ + if (!scsi_noretry_cmd(scmd) || + scmd->device->expecting_media_change) { + scmd->device->expecting_media_change = 0; + return NEEDS_RETRY; + } else { + /* marked fast fail and not expected. */ + return SUCCESS; + } } else { /* * no more retries - report this one back to upper level. diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index d90fefffe31b..bb583e403b81 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -3642,6 +3642,8 @@ static int sd_resume(struct device *dev) if (!sdkp) /* E.g.: runtime resume at the start of sd_probe() */ return 0; + sdkp->device->expecting_media_change = 1; + if (!sdkp->device->manage_start_stop) return 0; diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index bc5909033d13..f5fc1af68e00 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -169,6 +169,7 @@ struct scsi_device { * this device */ unsigned expecting_cc_ua:1; /* Expecting a CHECK_CONDITION/UNIT_ATTN * because we did a bus reset. */ + unsigned expecting_media_change:1; unsigned use_10_for_rw:1; /* first try 10-byte read / write */ unsigned use_10_for_ms:1; /* first try 10-byte mode sense/select */ unsigned set_dbd_for_ms:1; /* Set "DBD" field in mode sense */ --