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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_PASS 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 75306C169C4 for ; Tue, 12 Feb 2019 01:54:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4222E20836 for ; Tue, 12 Feb 2019 01:54:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="JdZSJk5r" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726821AbfBLByl (ORCPT ); Mon, 11 Feb 2019 20:54:41 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:43332 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726815AbfBLByl (ORCPT ); Mon, 11 Feb 2019 20:54:41 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x1C1nHrl006938; Tue, 12 Feb 2019 01:54:38 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=YJXzhy7WlbTUkMbSYIK8Xtmwi248YbHdbKAh+N2PN8Y=; b=JdZSJk5rhI5GCoAN6/fYvHl7yUwZRnaPFsUfhbHQ83s2BTX0Jy/ogR8aobA71yZ88Sfk PUCpj4YTl1kfRhn8rv3sPjlfN8mh8cbJR3WPXDXMBEpwpXsxqQ9Dg4ioToHYzj+TxLou 8MckK3+QPaGz/09bkCk6qv2rd8mamUesCNBOWyT6a+ejDpiNi+SDupaPraQI5e9td+py TqJ+vRVlo+mqkbJP0/TSkc+a/dyKGlZGieodgCaFCmYkDwjj+om4jseOaEaDKHcZ22bc dInyyBkBJjvxIjSqCwihWMMj08dSyaFA8fCN1kZ16aW+QlBGtW7kO0xy1DjMzPoZzlZS UA== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by userp2130.oracle.com with ESMTP id 2qhrek9802-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 12 Feb 2019 01:54:38 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x1C1sbt1008754 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 12 Feb 2019 01:54:38 GMT Received: from abhmp0002.oracle.com (abhmp0002.oracle.com [141.146.116.8]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x1C1sbEB011237; Tue, 12 Feb 2019 01:54:37 GMT Received: from [10.182.69.118] (/10.182.69.118) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 11 Feb 2019 17:54:37 -0800 Subject: Re: [PATCH] blk-mq: insert rq with DONTPREP to hctx dispatch list when requeue To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <1549863665-1691-1-git-send-email-jianchao.w.wang@oracle.com> <937e9207-dcf7-dab5-1917-8a10303edc67@kernel.dk> <82deee13-a4ff-9bf5-5e01-0e4df01b7ff7@kernel.dk> From: "jianchao.wang" Message-ID: <0ae89a37-7b6e-0cc4-f474-2e5c45cc1aec@oracle.com> Date: Tue, 12 Feb 2019 09:56:56 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9164 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902120011 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Jens Thanks for your kindly response. On 2/12/19 7:20 AM, Jens Axboe wrote: > On 2/11/19 4:15 PM, Jens Axboe wrote: >> On 2/11/19 8:59 AM, Jens Axboe wrote: >>> 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. >> >> This is probably better (and safer): > > Here's the one I wanted to send, not a half done one. Maybe I'll be > luckier this time around? > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 8f5b533764ca..35e6aba52808 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -737,12 +737,21 @@ 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 (!(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 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_DONTPREP) > + blk_mq_request_bypass_insert(rq, false); > + else > + blk_mq_sched_insert_request(rq, true, false, false); > } > > while (!list_empty(&rq_list)) { > The test is OK. And I will send out the V2 based on this. Thanks Jianchao