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[23.128.96.18]) by mx.google.com with ESMTP id 30si127590pgr.183.2021.10.27.07.31.30; Wed, 27 Oct 2021 07:32:06 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-ext4-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237613AbhJ0CzK (ORCPT + 99 others); Tue, 26 Oct 2021 22:55:10 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:55584 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236497AbhJ0CzK (ORCPT ); Tue, 26 Oct 2021 22:55:10 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0UtqE.Tu_1635303162; Received: from admindeMacBook-Pro-2.local(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0UtqE.Tu_1635303162) by smtp.aliyun-inc.com(127.0.0.1); Wed, 27 Oct 2021 10:52:43 +0800 Subject: Re: [Question] ext4/xfs: Default behavior changed after per-file DAX From: JeffleXu To: Theodore Ts'o , adilger.kernel@dilger.ca, "Darrick J. Wong" , ira.weiny@intel.com Cc: linux-xfs@vger.kernel.org, "linux-ext4@vger.kernel.org" , linux-fsdevel@vger.kernel.org, dan.j.williams@intel.com, Vivek Goyal , Christoph Hellwig References: <26ddaf6d-fea7-ed20-cafb-decd63b2652a@linux.alibaba.com> Message-ID: Date: Wed, 27 Oct 2021 10:52:42 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <26ddaf6d-fea7-ed20-cafb-decd63b2652a@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Sorry for the noise. Ira Weiny had replied my previous mail [1] but unfortunately the reply was moved into junk box, and I didn't note that. [1] https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@redhat.com/T/#mb022959fe3b6e9b82e2b066dd8daa301cd2b2c53 On 10/26/21 10:12 PM, JeffleXu wrote: > Hi, > > Recently I'm working on supporting per-file DAX for virtiofs [1]. Vivek > Goyal and I are interested [2] why the default behavior has changed > since introduction of per-file DAX on ext4 and xfs [3][4]. > > That is, before the introduction of per-file DAX, when user doesn't > specify '-o dax', DAX is disabled for all files. After supporting > per-file DAX, when neither '-o dax' nor '-o dax=always|inode|never' is > specified, it actually works in a '-o dax=inode' way if the underlying > blkdev is DAX capable, i.e. depending on the persistent inode flag. That > is, the default behavior has changed from user's perspective. > > We are not sure if this is intentional or not. Appreciate if anyone > could offer some hint. > > > [1] https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@redhat.com/T/ > [2] > https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@redhat.com/T/#mf067498887ca2023c64c8b8f6aec879557eb28f8 > [3] 9cb20f94afcd2964944f9468e38da736ee855b19 ("fs/ext4: Make DAX mount > option a tri-state") > [4] 02beb2686ff964884756c581d513e103542dcc6a ("fs/xfs: Make DAX mount > option a tri-state") > > -- Thanks, Jeffle