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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 30F99C4360F for ; Fri, 15 Feb 2019 02:01:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 09B6621B1A for ; Fri, 15 Feb 2019 02:01:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731282AbfBOCBG (ORCPT ); Thu, 14 Feb 2019 21:01:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43398 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726360AbfBOCBF (ORCPT ); Thu, 14 Feb 2019 21:01:05 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A35AFC0AC371; Fri, 15 Feb 2019 02:01:03 +0000 (UTC) Received: from ming.t460p (ovpn-8-28.pek2.redhat.com [10.72.8.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4EA8A5D6B6; Fri, 15 Feb 2019 02:00:55 +0000 (UTC) Date: Fri, 15 Feb 2019 10:00:51 +0800 From: Ming Lei To: Jianchao Wang Cc: axboe@kernel.dk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Damien Le Moal Subject: Re: [PATCH V2] blk-mq: insert rq with DONTPREP to hctx dispatch list when requeue Message-ID: <20190215020049.GA21045@ming.t460p> References: <1549936585-1702-1-git-send-email-jianchao.w.wang@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1549936585-1702-1-git-send-email-jianchao.w.wang@oracle.com> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 15 Feb 2019 02:01:04 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Feb 12, 2019 at 09:56:25AM +0800, 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. scsi_mq_requeue_cmd() does uninit the request before requeuing, but __scsi_queue_insert doesn't do that. > 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. > > Suggested-by: Jens Axboe > Signed-off-by: Jianchao Wang > --- > V2: > - refactor the code based on Jens' suggestion > > block/blk-mq.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 8f5b533..9437a5e 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 (!(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, rq has contained some driver specific > + * data, so 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); > } Suppose it is one WRITE request to zone device, this way might break the order. Thanks, Ming