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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 600ABC433E0 for ; Tue, 30 Jun 2020 03:34:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43762206A5 for ; Tue, 30 Jun 2020 03:34:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729164AbgF3DeE (ORCPT ); Mon, 29 Jun 2020 23:34:04 -0400 Received: from comms.puri.sm ([159.203.221.185]:33008 "EHLO comms.puri.sm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728949AbgF3DeB (ORCPT ); Mon, 29 Jun 2020 23:34:01 -0400 Received: from localhost (localhost [127.0.0.1]) by comms.puri.sm (Postfix) with ESMTP id 046DEDF73A; Mon, 29 Jun 2020 20:33:30 -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 wD5O5quhdx5D; Mon, 29 Jun 2020 20:33:29 -0700 (PDT) Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release To: Alan Stern Cc: Bart Van Assche , jejb@linux.ibm.com, Can Guo , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@puri.sm References: <20200623111018.31954-1-martin.kepplinger@puri.sm> <1379e21d-c51a-3710-e185-c2d7a9681fb7@acm.org> <20200626154441.GA296771@rowland.harvard.edu> <20200629161536.GA405175@rowland.harvard.edu> From: Martin Kepplinger Autocrypt: addr=martin.kepplinger@puri.sm; keydata= mQINBFULfZABEADRxJqDOYAHfrp1w8Egcv88qoru37k1x0Ugy8S6qYtKLAAt7boZW+q5gPv3 Sj2KjfkWA7gotXpASN21OIfE/puKGwhDLAySY1DGNMQ0gIVakUO0ji5GJPjeB9JlmN5hbA87 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wrote: >>> Martin's best approach would be to add some debugging code to find out why >>> blk_queue_enter() isn't calling bkl_pm_request_resume(), or why that call >>> doesn't lead to pm_request_resume(). >>> >>> Alan Stern >>> >> >> Hi Alan, >> >> blk_queue_enter() always - especially when sd is runtime suspended and I >> try to mount as above - sets success to be true for me, so never >> continues down to bkl_pm_request_resume(). All I see is "PM: Removing >> info for No Bus:sda1". > > Aha. Looking at this more closely, it's apparent that the code in > blk-core.c contains a logic bug: It assumes that if the BLK_MQ_REQ_PREEMPT > flag is set then the request can be issued regardless of the queue's > runtime status. That is not correct when the queue is suspended. > > Below is my attempt to fix this up. I'm not sure that the patch is > entirely correct, but it should fix this logic bug. I would appreciate a > critical review. > > Martin, does this fix the problem? > not quite: mounting works and resuming itself indeed happens now when copying a file, but the I/O itself doesn't, but says "device offline or changed": [ 167.167615] sd 0:0:0:0: [sda] tag#0 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=0x08 cmd_age=0s [ 167.167630] sd 0:0:0:0: [sda] tag#0 Sense Key : 0x6 [current] [ 167.167638] sd 0:0:0:0: [sda] tag#0 ASC=0x28 ASCQ=0x0 [ 167.167648] sd 0:0:0:0: [sda] tag#0 CDB: opcode=0x28 28 00 00 00 24 c2 00 00 01 00 [ 167.167658] blk_update_request: I/O error, dev sda, sector 9410 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0 [ 167.178327] FAT-fs (sda1): FAT read failed (blocknr 1218) [ 167.183895] sd 0:0:0:0: [sda] tag#0 device offline or changed [ 167.189695] blk_update_request: I/O error, dev sda, sector 5101888 op 0x0:(READ) flags 0x80700 phys_seg 8 prio class 0 [ 167.200510] sd 0:0:0:0: [sda] tag#0 device offline or changed and a later try to copy a file only yields (mostly my own debug prints): [ 371.110798] blk_queue_enter: wait_event: pm=0 [ 371.300666] scsi_runtime_resume [ 371.303834] scsi_runtime_resume [ 371.307007] scsi_runtime_resume [ 371.310213] sd 0:0:0:0: [sda] tag#0 device offline or changed [ 371.316011] blk_update_request: I/O error, dev sda, sector 5101888 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0 [ 372.560690] scsi_runtime_suspend [ 372.563968] scsi_runtime_suspend [ 372.567237] scsi_runtime_suspend thanks Alan for taking the time and trying to fix this! you're close. what is missing? martin