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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1BED5C47082 for ; Tue, 8 Jun 2021 15:04:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEBC161287 for ; Tue, 8 Jun 2021 15:04:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233706AbhFHPGB (ORCPT ); Tue, 8 Jun 2021 11:06:01 -0400 Received: from mail-pj1-f45.google.com ([209.85.216.45]:36713 "EHLO mail-pj1-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233606AbhFHPGB (ORCPT ); Tue, 8 Jun 2021 11:06:01 -0400 Received: by mail-pj1-f45.google.com with SMTP id d5-20020a17090ab305b02901675357c371so13918643pjr.1 for ; Tue, 08 Jun 2021 08:04:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=xWQnAJeNzdp06JbxiO/z5U+GoJHTfCjMg6UZSsFqdJI=; b=f225e0SXNQ9fNa7HTW8A7DmEx051WJmUHqThSjOjmffD8KwWlCMA6SsSIDVWsNhIZ7 iPZqKZLRwpJF72r+ASzXu8NCiiBXAkm5UTp201qHdRbpYUt4GoCckPJd1Sw3eZGMPcaI hVCWh3rIArv/FJjYHEabr4eS5e2kKaKWCOM+hdW4bWVUXHxTSNdv6BobxvQHl59xs7wr T91RMbceJrvlleZQE8g7A8HIrpRQgW9AkljnJv81hmP+UP42uNMr2UUb4rxspl+ZQHm2 A+FCEf1vquDxGNWkmGkBtr0czBxtE+ROvAW6MLZuV2QE7aU6isoFRBzkiFGN+r1KBx0y NPDw== X-Gm-Message-State: AOAM531aXb1ysVsvMJTRiL7OTKuatSJN8taHlm432JG9gc+Og//Xh9Yn HrtwoCZVM/yEYqIjeWrw+wk= X-Google-Smtp-Source: ABdhPJzE0FaTajSMTSNpnP3Rsb+81e8fH22xlG4tSidFj0SV3uX8zxJMnMy9SQpC+1eIZIAFN6d3lg== X-Received: by 2002:a17:902:44:b029:ee:9107:4242 with SMTP id 62-20020a1709020044b02900ee91074242mr108535pla.18.1623164643380; Tue, 08 Jun 2021 08:04:03 -0700 (PDT) Received: from [192.168.3.217] (c-73-241-217-19.hsd1.ca.comcast.net. [73.241.217.19]) by smtp.gmail.com with ESMTPSA id i8sm11735001pgt.58.2021.06.08.08.04.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Jun 2021 08:04:02 -0700 (PDT) Subject: Re: [PATCH V2 1/2] block: fix race between adding/removing rq qos and normal IO To: Ming Lei , Jens Axboe , Christoph Hellwig Cc: linux-block@vger.kernel.org, Yi Zhang References: <20210608071903.431195-1-ming.lei@redhat.com> <20210608071903.431195-2-ming.lei@redhat.com> From: Bart Van Assche Message-ID: <897fbf4d-569d-afae-c20d-745c8e2965d2@acm.org> Date: Tue, 8 Jun 2021 08:04:00 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <20210608071903.431195-2-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 6/8/21 12:19 AM, Ming Lei wrote: > static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos) > { > + /* > + * No IO can be in-flight when adding rqos, so freeze queue, which > + * is fine since we only support rq_qos for blk-mq queue > + */ > + blk_mq_freeze_queue(q); > rqos->next = q->rq_qos; > q->rq_qos = rqos; > + blk_mq_unfreeze_queue(q); > > if (rqos->ops->debugfs_attrs) > blk_mq_debugfs_register_rqos(rqos); > @@ -110,12 +117,18 @@ static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos) > { > struct rq_qos **cur; > > + /* > + * No IO can be in-flight when removing rqos, so freeze queue, > + * which is fine since we only support rq_qos for blk-mq queue > + */ > + blk_mq_freeze_queue(q); > for (cur = &q->rq_qos; *cur; cur = &(*cur)->next) { > if (*cur == rqos) { > *cur = rqos->next; > break; > } > } > + blk_mq_unfreeze_queue(q); > > blk_mq_debugfs_unregister_rqos(rqos); > } Although this patch looks like an improvement to me, I think we also need protection against concurrent rq_qos_add() and rq_qos_del() calls, e.g. via a mutex. Thanks, Bart.