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=-6.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 F2C21C433E0 for ; Tue, 22 Dec 2020 02:14:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7F4E22B3B for ; Tue, 22 Dec 2020 02:14:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725899AbgLVCNp (ORCPT ); Mon, 21 Dec 2020 21:13:45 -0500 Received: from mail-pf1-f171.google.com ([209.85.210.171]:33690 "EHLO mail-pf1-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725852AbgLVCNp (ORCPT ); Mon, 21 Dec 2020 21:13:45 -0500 Received: by mail-pf1-f171.google.com with SMTP id h186so7587398pfe.0; Mon, 21 Dec 2020 18:13:29 -0800 (PST) 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=ktaJOPLdx7KbKAhrChNKMTdd4WLo3ab5PljsYO04KSI=; b=BYj6N2nAv+6lr9rwwVTzgJzwiORvQcz6Lmuh9doG84ZFcdQnBPpR8W0F2qUVVcwJmR 1jYyFymX+RBmnrjV4o6ZrisZeMvtqWrH7jwcJIEZugemn/6xF/FOtapW4z0cRH07LtBY r0YXNlZ5IeJSVsNMOkiCaDrpgqyCHQcvx2G5t8ALEbZgfjFZ65ccjkrDmBwLW3PkM3in hn/BjPpiozU6SHESijkGWgc1QkDdltPk6d21j6WBz/fdQcNzJoLg6vu04YxZYDmDMv+H lcBw8Ihjv0pzkTVTheEgF7LlegsEzeFzfFyeBB9m5MYJZGvxg4g9V8UosgDQ4FF2RvKh RfIA== X-Gm-Message-State: AOAM532czLAueoIadzwnbhoS5TNkh4OzDc0BVStFJehJKpKOAOGP6NbD Ohg1VLiJeJgF6y2PUx9BWs0= X-Google-Smtp-Source: ABdhPJzBQHc7rK8XtJVOGQB8AnH4ayiDz325B/0erk8X4jzjqNKhiQh/+khT3EpYMrI/3yX9hzK9vw== X-Received: by 2002:a63:1401:: with SMTP id u1mr6048718pgl.229.1608603184210; Mon, 21 Dec 2020 18:13:04 -0800 (PST) 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 b12sm17620492pft.114.2020.12.21.18.13.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Dec 2020 18:13:02 -0800 (PST) Subject: Re: [RFC PATCH v2 2/2] blk-mq: Lockout tagset iter when freeing rqs To: John Garry , axboe@kernel.dk, ming.lei@redhat.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, hch@lst.de, hare@suse.de, ppvk@codeaurora.org, kashyap.desai@broadcom.com, linuxarm@huawei.com References: <1608203273-170555-1-git-send-email-john.garry@huawei.com> <1608203273-170555-3-git-send-email-john.garry@huawei.com> <4d2004bb-4444-7a63-7c72-1759e3037cfd@huawei.com> <31de2806-bbc1-dcc3-b9eb-ce9257420432@acm.org> From: Bart Van Assche Message-ID: Date: Mon, 21 Dec 2020 18:13:01 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: 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 12/21/20 10:47 AM, John Garry wrote: > Yes, I agree, and I'm not sure what I wrote to give that impression. > > About "root partition", above, I'm just saying that / is mounted on a > sda partition: > > root@ubuntu:/home/john# mount | grep sda > /dev/sda2 on / type ext4 (rw,relatime,errors=remount-ro,stripe=32) > /dev/sda1 on /boot/efi type vfat > (rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro) Hi John, Thanks for the clarification. I want to take back my suggestion about adding rcu_read_lock() / rcu_read_unlock() in blk_mq_tagset_busy_iter() since it is not allowed to sleep inside an RCU read-side critical section, since blk_mq_tagset_busy_iter() is used in request timeout handling and since there may be blk_mq_ops.timeout implementations that sleep. Ming's suggestion to serialize blk_mq_tagset_busy_iter() and blk_mq_free_rqs() looks interesting to me. Thanks, Bart.