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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 B023EC433B4 for ; Wed, 21 Apr 2021 00:02:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D97B6141C for ; Wed, 21 Apr 2021 00:02:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233992AbhDUADV (ORCPT ); Tue, 20 Apr 2021 20:03:21 -0400 Received: from mail-pl1-f169.google.com ([209.85.214.169]:34454 "EHLO mail-pl1-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234453AbhDUADU (ORCPT ); Tue, 20 Apr 2021 20:03:20 -0400 Received: by mail-pl1-f169.google.com with SMTP id t22so20271234ply.1 for ; Tue, 20 Apr 2021 17:02:48 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=1Di2CfCL8byMqwy8hyI2sa5jc4+9OFqr/SRk2zQLdeM=; b=Be//+5Kzgfyhyek2MfNdOeOR885lbyMu40idi4VddoPjTBpPBOJdywAYU0ceeKGxvn abUStz+eicnIFLi0DPt3mJK41HiKHIsQT0igTfNw4oUvOLfl+ARhE+zs+/UF9w9JpXWF CoRvhtcvdjYanvetHkDtx+tMpoXHHAzrudgcZypcBW+8BfYFf+gZ5MUO3lJTb4gm7MwN oPoJPlsfaCacJAABgKDf3pOURqxlUxv3Cl0I9yu4FU70rqUylcDd4oa7QH9fiHltXJS7 unT8hfXmI1xJAKEf0mjFbrOZIEEQTqMT1bAska+9Vd5tKRd/klnsrbA2ipvjGVIIvCBm WzcA== X-Gm-Message-State: AOAM5315ZtlPXyUEeM9DmkRkLqMYIdloPkcsfW53h+VWiXuGQIdOiUGJ Im2xKu5+pMWqwK0MnfvFlXc= X-Google-Smtp-Source: ABdhPJxfyTo7XojfssKUK2iHKCKuXVlqbyWus86u58yQlhdaawkPQnY1WRA/NH9dcKcZ2UYo+n5O5A== X-Received: by 2002:a17:902:c745:b029:eb:6fc0:39e7 with SMTP id q5-20020a170902c745b02900eb6fc039e7mr30722131plq.82.1618963368393; Tue, 20 Apr 2021 17:02:48 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net ([2601:647:4000:d7:6cb:4566:9005:c2af]) by smtp.gmail.com with ESMTPSA id 33sm149560pgq.21.2021.04.20.17.02.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Apr 2021 17:02:47 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Daniel Wagner , Bart Van Assche , Khazhismel Kumykov , Shin'ichiro Kawasaki , "Martin K . Petersen" , Ming Lei , Hannes Reinecke , Johannes Thumshirn , John Garry Subject: [PATCH v7 4/5] blk-mq: Make it safe to use RCU to iterate over blk_mq_tag_set.tag_list Date: Tue, 20 Apr 2021 17:02:34 -0700 Message-Id: <20210421000235.2028-5-bvanassche@acm.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210421000235.2028-1-bvanassche@acm.org> References: <20210421000235.2028-1-bvanassche@acm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Since the next patch in this series will use RCU to iterate over tag_list, make this safe. Note: call_rcu() is already used to free the request queue. >From blk-sysfs.c: call_rcu(&q->rcu_head, blk_free_queue_rcu); See also: * Commit 705cda97ee3a ("blk-mq: Make it safe to use RCU to iterate over blk_mq_tag_set.tag_list"; v4.12). * Commit 08c875cbf481 ("block: Use non _rcu version of list functions for tag_set_list"; v5.9). Reviewed-by: Khazhismel Kumykov Tested-by: Shin'ichiro Kawasaki Cc: Christoph Hellwig Cc: Martin K. Petersen Cc: Shin'ichiro Kawasaki Cc: Ming Lei Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: John Garry Cc: Daniel Wagner Signed-off-by: Bart Van Assche --- block/blk-mq.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 8b59f6b4ec8e..7d2ea6357c7d 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2947,7 +2947,7 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q) struct blk_mq_tag_set *set = q->tag_set; mutex_lock(&set->tag_list_lock); - list_del(&q->tag_set_list); + list_del_rcu(&q->tag_set_list); if (list_is_singular(&set->tag_list)) { /* just transitioned to unshared */ set->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED; @@ -2955,7 +2955,11 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q) blk_mq_update_tag_set_shared(set, false); } mutex_unlock(&set->tag_list_lock); - INIT_LIST_HEAD(&q->tag_set_list); + /* + * Calling synchronize_rcu() and INIT_LIST_HEAD(&q->tag_set_list) is + * not necessary since blk_mq_del_queue_tag_set() is only called from + * blk_cleanup_queue(). + */ } static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,