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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 7E67CC10F05 for ; Wed, 27 Mar 2019 02:04:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F00A204EC for ; Wed, 27 Mar 2019 02:04:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="s5NnGnn1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731963AbfC0CEI (ORCPT ); Tue, 26 Mar 2019 22:04:08 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:35204 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727488AbfC0CEI (ORCPT ); Tue, 26 Mar 2019 22:04:08 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x2R23YEf065342; Wed, 27 Mar 2019 02:03:34 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=FGX4+B3Cf8XdJre/h3nKtNd2FVnzk4g8uz+ICXCesgs=; b=s5NnGnn1tXnI9hahPM70kgmdVdnwILxWuwmSYoZie4ZvBPMWVWP6l668Sol5D/fAPd02 Z9crOltgP1nLPPPuSp0ZvQZqA9wDspkQaeh0ifQ3ygHjTH8Kel2MzTo7ndRr5rZYIRgP 6f2ls04lVMwGfIwqdMjAr0KOXFqHD72BHD4F+zQlv3ptdTwodXiqavMfCdqyvPrvEcNn rhRTZXAHHmiy3UEj5MO1G7TNsbG+XXsRNz6sWLqwSBbFq0KvSB6Jo4QVeTWB4zvAkFNS s22pGyhVXVMeteb9MA5XdH5yLzsOMj0vB/l7T/DYhLi0zrD9JfVopNm2PVKuqPRyqfPf 4w== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by userp2120.oracle.com with ESMTP id 2re6djdw22-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 27 Mar 2019 02:03:34 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x2R23WS8022870 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 27 Mar 2019 02:03:33 GMT Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x2R23Q9r024593; Wed, 27 Mar 2019 02:03:26 GMT Received: from [10.182.71.8] (/10.182.71.8) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 26 Mar 2019 19:03:26 -0700 Subject: Re: [PATCH V2 7/8] nvme: use blk_mq_queue_tag_inflight_iter To: Keith Busch Cc: Jens Axboe , linux-block , James Smart , Bart Van Assche , Ming Lei , Josef Bacik , linux-nvme , Linux Kernel Mailing List , "Busch, Keith" , Hannes Reinecke , Johannes Thumshirn , Christoph Hellwig , Sagi Grimberg References: <1553492318-1810-1-git-send-email-jianchao.w.wang@oracle.com> <1553492318-1810-8-git-send-email-jianchao.w.wang@oracle.com> <20190325134917.GA4328@localhost.localdomain> <70e14e12-2ffc-37db-dd8f-229bc580546e@oracle.com> <20190326235726.GC4328@localhost.localdomain> From: "jianchao.wang" Message-ID: Date: Wed, 27 Mar 2019 10:03:26 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190326235726.GC4328@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9207 signatures=668685 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-1903270013 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Keith On 3/27/19 7:57 AM, Keith Busch wrote: > On Mon, Mar 25, 2019 at 08:05:53PM -0700, jianchao.wang wrote: >> What if there used to be a io scheduler and leave some stale requests of sched tags ? >> Or the nr_hw_queues was decreased and leave the hctx->fq->flush_rq ? > > Requests internally queued in scheduler or block layer are not eligible > for the nvme driver's iterator callback. We only use it to reclaim > dispatched requests that the target can't return, which only applies to > requests that must have a valid rq->tag value from hctx->tags. > >> The stable request could be some tings freed and used >> by others and the state field happen to be overwritten to non-zero... > > I am not sure I follow what this means. At least for nvme, every queue > sharing the same tagset is quiesced and frozen, there should be no > request state in flux at the time we iterate. > In nvme_dev_disable, when we try to reclaim the in-flight requests with blk_mq_tagset_busy_iter, the request_queues are quiesced but just start-freeze. We will try to _drain_ the in-flight requests for the _shutdown_ case when controller is not dead. For the reset case, there still could be someone escapes the checking of queue freezing and enters blk_mq_make_request and tries to allocate tag, then we may get, generic_make_request nvme_dev_disable -> blk_queue_enter -> nvme_start_freeze (just start freeze, no drain) -> nvme_stop_queues -> blk_mq_make_request - > blk_mq_get_request -> blk_mq_tagset_busy_iter -> blk_mq_get_tag 　　 -> bt_tags_for_each 　　　 -> bt_tags_iter 　　 -> rq = tags->rqs[] ---> [1] -> blk_mq_rq_ctx_init -> data->hctx->tags->rqs[rq->tag] = rq; The rq got on position [1] could be a stale request that has been freed due to, 1. a hctx->fq.flush_rq of dead request_queue that shares the same tagset 2. a removed io scheduler's sched request And this stale request may have been used by others and the request->state is changed to a non-zero value and passes the checking of blk_mq_request_started and then it will be handled by nvme_cancel_request. Thanks Jianchao