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=-7.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,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 BF96CC282C0 for ; Sat, 26 Jan 2019 01:16:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A59C218F0 for ; Sat, 26 Jan 2019 01:16:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="yvTCXHIA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726030AbfAZBQk (ORCPT ); Fri, 25 Jan 2019 20:16:40 -0500 Received: from aserp2130.oracle.com ([141.146.126.79]:44688 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725550AbfAZBQk (ORCPT ); Fri, 25 Jan 2019 20:16:40 -0500 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.22/8.16.0.22) with SMTP id x0Q1EZUW042586; Sat, 26 Jan 2019 01:16:33 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=VN91eYyKNwPyf7kNfseFO0B3YkS+G7V0IlqHECbWM44=; b=yvTCXHIA66wHd5Xf7M6/xB/SwtEGuhxVCutJz/mAGnLPaB0sliDEEHY42A2pZD96VbGA urvmmoARBST+qPSLRYRcmNhixdWJcVfVqyWft//0/3OaEtfs/l2hlmb3NoPhNlLhGsPF 6Hs2VehR8a38C2OFeVHYO/bMYI8IXVh/ldaEjMkIq/ZzGshCLNsPq6+EKTjzv+wNzF09 44RzOpBtkDp1GMCAXg/ROp1buSv5x3InfrPXyAg7HVsV4cc2UcLrHwxk67WmkMqaquj4 +cr5P+DgMpcHApM5OiMd5WFBJAo5Sou8dVkhtN/YHOKZPSVfCpnPauRHoGZMCrKGlPbW Yw== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by aserp2130.oracle.com with ESMTP id 2q8d2dr2h2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 26 Jan 2019 01:16:33 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x0Q1GWe7011432 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 26 Jan 2019 01:16:32 GMT Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x0Q1GVpl015879; Sat, 26 Jan 2019 01:16:31 GMT Received: from [10.191.30.196] (/10.191.30.196) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 25 Jan 2019 17:16:31 -0800 Subject: Re: fsync hangs after scsi rejected a request To: Florian Stecker , Ming Lei Cc: Linux SCSI List , "Martin K. Petersen" , Bart Van Assche , linux-block References: <70df6d90-31eb-96f4-908d-462ea58dea6e@florianstecker.de> <4b631218-49ee-c3ed-46be-17f9d30b663f@florianstecker.de> From: "jianchao.wang" Message-ID: <3d921990-06c4-4662-2853-7667b4e9a462@oracle.com> Date: Sat, 26 Jan 2019 09:18:19 +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: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9147 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901260004 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 1/26/19 6:10 AM, Florian Stecker wrote: > > > On 1/25/19 10:05 AM, jianchao.wang wrote: >> >> >> On 1/25/19 4:56 PM, Florian Stecker wrote: >>> On 1/25/19 4:49 AM, jianchao.wang wrote: >>>> >>>> It sounds like not so easy to trigger. >>>> >>>> blk_mq_dispatch_rq_list >>>>     scsi_queue_rq >>>>        if (atomic_read(&sdev->device_busy) || >>>>          scsi_device_blocked(sdev)) >>>>          ret = BLK_STS_DEV_RESOURCE;             scsi_end_request >>>>                                                    __blk_mq_end_request >>>>                                                      blk_mq_sched_restart // clear RESTART >>>>                                                        blk_mq_run_hw_queue >>>>                                                    blk_mq_run_hw_queues >>>>       list_splice_init(list, &hctx->dispatch) >>>>     needs_restart = blk_mq_sched_needs_restart(hctx) >>>> >>>> The 'needs_restart' will be false, so the queue would be rerun. >>>> >>>> Thanks >>>> Jianchao >>> >>> Good point. So the RESTART flag is supposed to protect against this? Now I see, this is also sort of what the lengthy comment in blk_mq_dispatch_rq_list is saying. >>> >>> May I complain that this is very unintuitive (the queue gets rerun when the RESTART flag is _not_ set) and also unreliable, as not every caller of blk_mq_dispatch_rq_list seems to set the flag, and also it does not always get cleared in __blk_mq_end_request? >>> >>> __blk_mq_end_request does the following: >>> >>>      if (rq->end_io) { >>>          rq_qos_done(rq->q, rq); >>>          rq->end_io(rq, error); >>>      } else { >>>          if (unlikely(blk_bidi_rq(rq))) >>>              blk_mq_free_request(rq->next_rq); >>>          blk_mq_free_request(rq); >>>      } >>> >>> and blk_mq_free_request then calls blk_mq_sched_restart, which clears the flag. But in my case, rq->end_io != 0, so blk_mq_free_request is never called. >> >> So what is your rq->end_io ? >> flush_end_io ? or mq_flush_data_end_io ? or other ? >> In normal case, the blk_mq_end_request should be finally invoked. >> >> Did you ever try the bfq io scheduler instead of mq-deadline ? >> >> Can you share your dmesg and config file here ? > > Sure. > > dmesg: https://urldefense.proofpoint.com/v2/url?u=https-3A__florianstecker.de_dmesg-2D2019-2D01-2D25.txt&d=DwIDaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=7WdAxUBeiTUTCy8v-7zXyr4qk7sx26ATvfo6QSTvZyQ&m=t_udGGsH8ivtjXHin4oQ4LxELuPoXbl_ARP7oSxiQ6k&s=DC2fhRw2g4haGhhHxOYyX4zD6FWQQ5YoERdfptVRHM4&e= > Note that no I/O scheduler is in use here, I deactivated them in a udev rule because I still want to be able to use my laptop. When I test this stuff I just reactivate mq-deadline manually. > > Config is the default in Arch Linux: https://urldefense.proofpoint.com/v2/url?u=https-3A__git.archlinux.org_svntogit_packages.git_tree_trunk_config-3Fh-3Dpackages_linux&d=DwIDaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=7WdAxUBeiTUTCy8v-7zXyr4qk7sx26ATvfo6QSTvZyQ&m=t_udGGsH8ivtjXHin4oQ4LxELuPoXbl_ARP7oSxiQ6k&s=GjV_fyXaKZ8za8zdB_gqmKW7yBlbla2OHRaAT0iGZkc&e= > > The problem also appears with BFQ. > > And rq->end_io is set to mq_flush_data_end_io when this happens. The only point I see where this function could invoke blk_mq_end_request is via blk_flush_complete_seq, but it does so only if seq == REQ_FSEQ_DONE. However, seq is REQ_FSEQ_POSTFLUSH for me (i.e. it just transitioned from REQ_FSEQ_DATA to REQ_FSEQ_POSTFLUSH). Could it be this scenario ? data + post flush blk_flush_complete_seq a flush case REQ_FSEQ_DATA blk_flush_queue_rq finally issued to driver blk_mq_dispatch_rq_list try to issue a flush req failed due to NON-NCQ command due to RESTART is set, do nothing req complete req->end_io（） // doesn't check RESTART mq_flush_data_end_io 　 blk_flush_complete_seq case REQ_FSEQ_POSTFLUSH blk_kick_flush do nothing because previous flush has not been completed, so flush_pending_idx != flush_running_idx Thanks Jianchao >> >