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=-12.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 0DD11C433E0 for ; Tue, 28 Jul 2020 14:13:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7C47206F5 for ; Tue, 28 Jul 2020 14:13:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730333AbgG1ONQ (ORCPT ); Tue, 28 Jul 2020 10:13:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:33168 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730298AbgG1ONQ (ORCPT ); Tue, 28 Jul 2020 10:13:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4D5AFB1DD; Tue, 28 Jul 2020 14:13:25 +0000 (UTC) Subject: Re: [PATCH] block: Use non _rcu version of list functions for tag_set_list To: Daniel Wagner , Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Ming Lei References: <20200728132951.29459-1-dwagner@suse.de> From: Hannes Reinecke Message-ID: Date: Tue, 28 Jul 2020 16:13:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200728132951.29459-1-dwagner@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 7/28/20 3:29 PM, Daniel Wagner wrote: > tag_set_list is only accessed under the tag_set_lock lock. There is > no need for using the _rcu list functions. > > The _rcu list function were introduced to allow read access to the > tag_set_list protected under RCU, see 705cda97ee3a ("blk-mq: Make it > safe to use RCU to iterate over blk_mq_tag_set.tag_list") and > 05b79413946d ("Revert "blk-mq: don't handle TAG_SHARED in restart""). > Those changes got reverted later but the cleanup commit missed a > couple of places to undo the changes. > > Fixes: 97889f9ac24f ("blk-mq: remove synchronize_rcu() from blk_mq_del_queue_tag_set()" > Cc: Ming Lei > Signed-off-by: Daniel Wagner > --- > block/blk-mq.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index e32cb0217135..14ee7506f32f 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2792,7 +2792,7 @@ 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_rcu(&q->tag_set_list); > + list_del(&q->tag_set_list); > if (list_is_singular(&set->tag_list)) { > /* just transitioned to unshared */ > set->flags &= ~BLK_MQ_F_TAG_SHARED; > @@ -2819,7 +2819,7 @@ static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set, > } > if (set->flags & BLK_MQ_F_TAG_SHARED) > queue_set_hctx_shared(q, true); > - list_add_tail_rcu(&q->tag_set_list, &set->tag_list); > + list_add_tail(&q->tag_set_list, &set->tag_list); > > mutex_unlock(&set->tag_list_lock); > } > Indeed. Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer