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=-4.0 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_PASS autolearn=unavailable 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 6B180C169C4 for ; Mon, 11 Feb 2019 15:59:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 38D0A218D8 for ; Mon, 11 Feb 2019 15:59:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="eOSFAq41" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730873AbfBKP7g (ORCPT ); Mon, 11 Feb 2019 10:59:36 -0500 Received: from mail-it1-f193.google.com ([209.85.166.193]:56103 "EHLO mail-it1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730114AbfBKP7e (ORCPT ); Mon, 11 Feb 2019 10:59:34 -0500 Received: by mail-it1-f193.google.com with SMTP id f18so16459665itb.5 for ; Mon, 11 Feb 2019 07:59:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=F04iFmw5as0JwRGyMGw9f6xTEAeCIzyG3ctTbOKxOhQ=; b=eOSFAq41ffwj0VS2QVCR6YByB0twcGu1osYkNYMNUAXGMMgZUN0z5YsarWSxZS2PCk VhPfTSKV80bVPU4eqrA0w6HJvy0JPLNAHF+Po/niSLA9xh33STp5vtvD4f6F6VzNCPfz LchH3mqVvChh41xr1i6IZWHOjHgD6aEZqWWPUzLgwtwPG9GT6J1khjm+Ov8nx4iMrroG izkZP1u0Z/2qEIEohOevhnyvTJ5NGKBSJpvRbefg9wkJnh3hbyCiHOm6rKVmKIlqCYtP D70lhEdMHrGLn4tpDbH+TGx0iLSIRlFzigd/YI3IJYPSQU5M1gBb1Ko3XmvT9RKz4Zsv Ol6g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=F04iFmw5as0JwRGyMGw9f6xTEAeCIzyG3ctTbOKxOhQ=; b=bS7Sz9IetfEKw/evexXGmZTphF/AjPr+gQ4F8MsEgdQlXpaZuRgdrfNKg98+I0+bTh FY5l/dTR8F46wBwg1B/sgf0C/89ZC5uAQm9CibWLFgV+WMRA8Nz8iDpK+rxgNsmRsD1t wHu6k6yVOgWMlKaTMWJKRNE0JopOqBTOC6+bysNeQ1bW+X2ZfG67BZ0FGxX+vxzofkaS hfK1lQhLebJLZBH6qd739QLcKgYUMgNH9fhHVK+vV0GNpAvZvSc1+vr9M6a/tltsJ2k3 Hj8JiuOFPmHGknV10YRskb+jIdsCFa0SOd66//8kB6g8MwmiyBE+RionebaR8/jfB5pS THtQ== X-Gm-Message-State: AHQUAuZOV8RTJvDXoiyr1Fe5q5fenhSzVUa1l7uzEpsH48gDnztZ3qaT z7ekjtQAmERem9mZvrLS2U7Drw== X-Google-Smtp-Source: AHgI3IacriPZPD6nqnkoI7fWdojvHgGOsMRdbWNYCsCmwokZ2WG0dnNuz2U+16SMEwnipXtLsDRHoA== X-Received: by 2002:a5d:9913:: with SMTP id x19mr16828644iol.99.1549900773398; Mon, 11 Feb 2019 07:59:33 -0800 (PST) Received: from [192.168.1.158] ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id e19sm4577174iob.70.2019.02.11.07.59.31 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Feb 2019 07:59:32 -0800 (PST) Subject: Re: [PATCH] blk-mq: insert rq with DONTPREP to hctx dispatch list when requeue To: Jianchao Wang Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <1549863665-1691-1-git-send-email-jianchao.w.wang@oracle.com> From: Jens Axboe Message-ID: <937e9207-dcf7-dab5-1917-8a10303edc67@kernel.dk> Date: Mon, 11 Feb 2019 08:59:31 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <1549863665-1691-1-git-send-email-jianchao.w.wang@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2/10/19 10:41 PM, Jianchao Wang wrote: > When requeue, if RQF_DONTPREP, rq has contained some driver > specific data, so insert it to hctx dispatch list to avoid any > merge. Take scsi as example, here is the trace event log (no > io scheduler, because RQF_STARTED would prevent merging), > > kworker/0:1H-339 [000] ...1 2037.209289: block_rq_insert: 8,0 R 4096 () 32768 + 8 [kworker/0:1H] > scsi_inert_test-1987 [000] .... 2037.220465: block_bio_queue: 8,0 R 32776 + 8 [scsi_inert_test] > scsi_inert_test-1987 [000] ...2 2037.220466: block_bio_backmerge: 8,0 R 32776 + 8 [scsi_inert_test] > kworker/0:1H-339 [000] .... 2047.220913: block_rq_issue: 8,0 R 8192 () 32768 + 16 [kworker/0:1H] > scsi_inert_test-1996 [000] ..s1 2047.221007: block_rq_complete: 8,0 R () 32768 + 8 [0] > scsi_inert_test-1996 [000] .Ns1 2047.221045: block_rq_requeue: 8,0 R () 32776 + 8 [0] > kworker/0:1H-339 [000] ...1 2047.221054: block_rq_insert: 8,0 R 4096 () 32776 + 8 [kworker/0:1H] > kworker/0:1H-339 [000] ...1 2047.221056: block_rq_issue: 8,0 R 4096 () 32776 + 8 [kworker/0:1H] > scsi_inert_test-1986 [000] ..s1 2047.221119: block_rq_complete: 8,0 R () 32776 + 8 [0] > > (32768 + 8) was requeued by scsi_queue_insert and had RQF_DONTPREP. > Then it was merged with (32776 + 8) and issued. Due to RQF_DONTPREP, > the sdb only contained the part of (32768 + 8), then only that part > was completed. The lucky thing was that scsi_io_completion detected > it and requeued the remaining part. So we didn't get corrupted data. > However, the requeue of (32776 + 8) is not expected. Good catch, but how about something like this? Makes it more integrated, I think that's cleaner. diff --git a/block/blk-mq.c b/block/blk-mq.c index 44d471ff8754..4c26bbb4330f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -737,12 +737,20 @@ static void blk_mq_requeue_work(struct work_struct *work) spin_unlock_irq(&q->requeue_lock); list_for_each_entry_safe(rq, next, &rq_list, queuelist) { - if (!(rq->rq_flags & RQF_SOFTBARRIER)) + /* + * If RQF_DONTPREP is set, rq may contain some driver + * specific data. Insert it to hctx dispatch list to avoid + * any merge. + */ + if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP))) continue; rq->rq_flags &= ~RQF_SOFTBARRIER; list_del_init(&rq->queuelist); - blk_mq_sched_insert_request(rq, true, false, false); + if (rq->rq_flags & RQF_SOFTBARRIER) + blk_mq_sched_insert_request(rq, true, false, false); + else + blk_mq_request_bypass_insert(rq, false); } while (!list_empty(&rq_list)) { -- Jens Axboe