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=-5.3 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 5CE4AC2D0E4 for ; Tue, 24 Nov 2020 03:12:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06B8F20705 for ; Tue, 24 Nov 2020 03:12:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728692AbgKXDMW (ORCPT ); Mon, 23 Nov 2020 22:12:22 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:7970 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728106AbgKXDMV (ORCPT ); Mon, 23 Nov 2020 22:12:21 -0500 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4Cg8Fd4zNjzhdMV; Tue, 24 Nov 2020 11:12:05 +0800 (CST) Received: from [10.136.114.67] (10.136.114.67) by smtp.huawei.com (10.3.19.211) with Microsoft SMTP Server (TLS) id 14.3.487.0; Tue, 24 Nov 2020 11:12:14 +0800 Subject: Re: [PATCH] f2fs: change to use rwsem for cp_mutex To: David Laight , 'Sahitya Tummala' , Jaegeuk Kim , "linux-f2fs-devel@lists.sourceforge.net" CC: "linux-kernel@vger.kernel.org" References: <1606109312-1944-1-git-send-email-stummala@codeaurora.org> <7f5213fb9b334d1290f019ab8ed6ee71@AcuMS.aculab.com> From: Chao Yu Message-ID: Date: Tue, 24 Nov 2020 11:12:14 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <7f5213fb9b334d1290f019ab8ed6ee71@AcuMS.aculab.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.136.114.67] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/11/24 1:05, David Laight wrote: > From: Sahitya Tummala >> Sent: 23 November 2020 05:29 >> >> Use rwsem to ensure serialization of the callers and to avoid >> starvation of high priority tasks, when the system is under >> heavy IO workload. > > I can't see any read lock requests. > > So why the change? Hi David, You can check the context of this patch in below link: https://lore.kernel.org/linux-f2fs-devel/8e094021b958f9fe01df1183a2677882@codeaurora.org/T/#t BTW, the root cause here is that mutex lock won't serialize callers, so there could be potential starvation problem when this lock is always grabbed by high priority tasks. Thanks,