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=-3.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_GIT 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 818D2C10F00 for ; Fri, 15 Mar 2019 09:06:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 512092184C for ; Fri, 15 Mar 2019 09:06:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="afodna/o" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728593AbfCOJGh (ORCPT ); Fri, 15 Mar 2019 05:06:37 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:40494 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727501AbfCOJGh (ORCPT ); Fri, 15 Mar 2019 05:06:37 -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 x2F8xHq8027924; Fri, 15 Mar 2019 09:06:20 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id; s=corp-2018-07-02; bh=ooKzMHXjxB1hW4mS22uZ/3/Gq8wyTQbRb/0fnDdxmdE=; b=afodna/opPv022Ix7KYXTzEzAm00+2z1BrogluY1JNaUEaEt0/RWrcDCD8omkfmLna1X P2VC9FKonyna4rKupgiy4aLSlA/UP5UQcJjyy13AEnDj2PrEkQsbOrazBS4JykfymguQ JY5B9ptt9z1z2mNSgsp6kBhetadJheDvfFtFylfFlAaqox4aM9AL3lpbhcKUQz8fxskd 4HXmIMc7t1JjMW9BIhG7b07hpZ8IqZQafBzEBn/cXQs3S+uPO2H2OdOmqCO13/+fbBDh ufPIOfOz8ZdyqjcciwdCBzcsqWjxRdYgkKcGEdYH769Wuz4+cXGTfZgVyY8IXBDoX7DH gg== Received: from aserv0021.oracle.com (aserv0021.oracle.com [141.146.126.233]) by userp2120.oracle.com with ESMTP id 2r464rwhsu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 15 Mar 2019 09:06:19 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x2F96DmS007350 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 15 Mar 2019 09:06:13 GMT Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x2F968CE005175; Fri, 15 Mar 2019 09:06:09 GMT Received: from will-ThinkCentre-M93p.cn.oracle.com (/10.182.71.12) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 15 Mar 2019 09:06:08 +0000 From: Jianchao Wang To: axboe@kernel.dk Cc: hch@lst.de, jthumshirn@suse.de, hare@suse.de, josef@toxicpanda.com, bvanassche@acm.org, sagi@grimberg.me, keith.busch@intel.com, jsmart2021@gmail.com, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/8]: blk-mq: use static_rqs to iterate busy tags Date: Fri, 15 Mar 2019 16:57:36 +0800 Message-Id: <1552640264-26101-1-git-send-email-jianchao.w.wang@oracle.com> X-Mailer: git-send-email 2.7.4 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9195 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=868 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903150067 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jens As we know, there is a risk of accesing stale requests when iterate in-flight requests with tags->rqs[] and this has been talked in following thread, [1] https://marc.info/?l=linux-scsi&m=154511693912752&w=2 [2] https://marc.info/?l=linux-block&m=154526189023236&w=2 A typical sence could be blk_mq_get_request blk_mq_queue_tag_busy_iter -> blk_mq_get_tag -> bt_for_each -> bt_iter -> rq = taags->rqs[] -> rq->q -> blk_mq_rq_ctx_init -> data->hctx->tags->rqs[rq->tag] = rq; The root cause is that there is a window between set bit on tag sbitmap and set tags->rqs[]. This patch would fix this issue by iterating requests with tags->static_rqs[] instead of tags->rqs[] which would be changed dynamically. Moreover, we will try to get a non-zero q_usage_counter before access hctxs and tags and thus could avoid the race with updating nr_hw_queues, switching io scheduler and even queue clean up which are all under a frozen and drained queue. The 1st patch get rid of the useless of synchronize_rcu in __blk_mq_update_nr_hw_queues The 2nd patch modify the blk_mq_queue_tag_busy_iter to use tags->static_rqs[] instead of tags->rqs[] to iterate the busy tags. The 3rd ~ 7th patch change the blk_mq_tagset_busy_iter to blk_mq_queue_tag_busy_iter which is safer The 8th patch get rid of the blk_mq_tagset_busy_iter. Jianchao Wang(8) blk-mq: get rid of the synchronize_rcu in blk-mq: change the method of iterating busy tags of a blk-mq: use blk_mq_queue_tag_busy_iter in debugfs mtip32xx: use blk_mq_queue_tag_busy_iter nbd: use blk_mq_queue_tag_busy_iter skd: use blk_mq_queue_tag_busy_iter nvme: use blk_mq_queue_tag_busy_iter blk-mq: remove blk_mq_tagset_busy_iter diff stat block/blk-mq-debugfs.c | 4 +- block/blk-mq-tag.c | 173 +++++++++++++++++++++++++------------------------------------------------------------- block/blk-mq-tag.h | 2 - block/blk-mq.c | 35 ++++++------------ drivers/block/mtip32xx/mtip32xx.c | 8 ++-- drivers/block/nbd.c | 2 +- drivers/block/skd_main.c | 4 +- drivers/nvme/host/core.c | 12 ++++++ drivers/nvme/host/fc.c | 12 +++--- drivers/nvme/host/nvme.h | 2 + drivers/nvme/host/pci.c | 5 ++- drivers/nvme/host/rdma.c | 6 +-- drivers/nvme/host/tcp.c | 5 ++- drivers/nvme/target/loop.c | 6 +-- include/linux/blk-mq.h | 7 ++-- 15 files changed, 105 insertions(+), 178 deletions(- Thanks Jianchao