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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C352C433F5 for ; Tue, 4 Oct 2022 04:13:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229763AbiJDENT (ORCPT ); Tue, 4 Oct 2022 00:13:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229697AbiJDEM4 (ORCPT ); Tue, 4 Oct 2022 00:12:56 -0400 Received: from esa9.hc1455-7.c3s2.iphmx.com (esa9.hc1455-7.c3s2.iphmx.com [139.138.36.223]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 108C326554; Mon, 3 Oct 2022 21:12:54 -0700 (PDT) X-IronPort-AV: E=McAfee;i="6500,9779,10489"; a="79114693" X-IronPort-AV: E=Sophos;i="5.93,366,1654527600"; d="scan'208";a="79114693" Received: from unknown (HELO yto-r1.gw.nic.fujitsu.com) ([218.44.52.217]) by esa9.hc1455-7.c3s2.iphmx.com with ESMTP; 04 Oct 2022 13:12:51 +0900 Received: from yto-m4.gw.nic.fujitsu.com (yto-nat-yto-m4.gw.nic.fujitsu.com [192.168.83.67]) by yto-r1.gw.nic.fujitsu.com (Postfix) with ESMTP id 27731DAFD0; Tue, 4 Oct 2022 13:12:51 +0900 (JST) Received: from m3003.s.css.fujitsu.com (m3003.s.css.fujitsu.com [10.128.233.114]) by yto-m4.gw.nic.fujitsu.com (Postfix) with ESMTP id 57365F0FB6; Tue, 4 Oct 2022 13:12:50 +0900 (JST) Received: from [10.14.75.87] (unknown [10.14.75.87]) by m3003.s.css.fujitsu.com (Postfix) with ESMTP id 8CF0F2005AD8; Tue, 4 Oct 2022 13:12:47 +0900 (JST) Message-ID: Date: Mon, 3 Oct 2022 21:12:46 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.13.1 Subject: Re: [PATCH] xfs: fail dax mount if reflink is enabled on a partition Content-Language: en-US To: "Darrick J. Wong" Cc: =?UTF-8?B?WWFuZywgWGlhby/mnagg5pmT?= , Brian Foster , "hch@infradead.org" , =?UTF-8?B?UnVhbiwgU2hpeWFuZy/pmK4g5LiW6Ziz?= , "linux-kernel@vger.kernel.org" , "linux-xfs@vger.kernel.org" , "nvdimm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "david@fromorbit.com" , zwisler@kernel.org, Jeff Moyer , dm-devel@redhat.com, toshi.kani@hpe.com References: <7fdc9e88-f255-6edb-7964-a5a82e9b1292@fujitsu.com> <76ea04b4-bad7-8cb3-d2c6-4ad49def4e05@fujitsu.com> <1444b9b5-363a-163c-0513-55d1ea951799@fujitsu.com> From: =?UTF-8?B?R290b3UsIFlhc3Vub3JpL+S6lOWztiDlurfmloc=?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/10/03 17:12, Darrick J. Wong wrote: > On Fri, Sep 30, 2022 at 09:56:41AM +0900, Gotou, Yasunori/五島 康文 wrote: >> Hello everyone, >> >> On 2022/09/20 11:38, Yang, Xiao/杨 晓 wrote: >>> Hi Darrick, Brian and Christoph >>> >>> Ping. I hope to get your feedback. >>> >>> 1) I have confirmed that the following patch set did not change the test >>> result of generic/470 with thin-volume. Besides, I didn't see any >>> failure when running generic/470 based on normal PMEM device instaed of >>> thin-volume. >>> https://lore.kernel.org/linux-xfs/20211129102203.2243509-1-hch@lst.de/ >>> >>> 2) I can reproduce the failure of generic/482 without thin-volume. >>> >>> 3) Is it necessary to make thin-volume support DAX. Is there any use >>> case for the requirement? >> >> >> Though I asked other place(*), I really want to know the usecase of >> dm-thin-volume with DAX and reflink. >> >> >> In my understanding, dm-thin-volume seems to provide similar feature like >> reflink of xfs. Both feature provide COW update to reduce usage of >> its region, and snapshot feature, right? >> >> I found that docker seems to select one of them (or other feature which >> supports COW). Then user don't need to use thin-volume and reflink at same >> time. >> >> Database which uses FS-DAX may want to use snapshot for its data of FS-DAX, >> its user seems to be satisfied with reflink or thin-volume. >> >> So I could not find on what use-case user would like to use dm-thin-volume >> and reflink at same time. >> >> The only possibility is that the user has mistakenly configured dm-thinpool >> and reflink to be used at the same time, but if that is the case, it seems >> to be better for the user to disable one or the other. >> >> I really wander why dm-thin-volume must be used with reflik and FS-DAX. > > There isn't a hard requirement between fsdax and dm-thinp. The /test/ > needs dm-logwrites to check that write page faults on a MAP_SYNC > mmapping are persisted directly to disk. dm-logwrites requires a fast > way to zero an entire device for correct operation of the replay step, > and thinp is the only way to guarantee that. Thank you for your answer. But I still feel something is strange. Though dm-thinp may be good way to execute the test correctly, I suppose it seems to be likely a kind of workaround to pass the test, it may not be really required for actual users. Could you tell me why passing test by workaround is so necessary? Thanks, > > --D > >> If my understanding is something wrong, please correct me. >> >> (*)https://lore.kernel.org/all/TYWPR01MB1008258F474CA2295B4CD3D9B90549@TYWPR01MB10082.jpnprd01.prod.outlook.com/