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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D2697C433E0 for ; Sat, 13 Mar 2021 22:08:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90E3764EE1 for ; Sat, 13 Mar 2021 22:08:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234798AbhCMWID (ORCPT ); Sat, 13 Mar 2021 17:08:03 -0500 Received: from tartarus.angband.pl ([51.83.246.204]:41154 "EHLO tartarus.angband.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234758AbhCMWHh (ORCPT ); Sat, 13 Mar 2021 17:07:37 -0500 Received: from kilobyte by tartarus.angband.pl with local (Exim 4.94) (envelope-from ) id 1lLCJc-00GN3W-3k; Sat, 13 Mar 2021 23:00:56 +0100 Date: Sat, 13 Mar 2021 23:00:56 +0100 From: Adam Borowski To: Neal Gompa Cc: Matthew Wilcox , Goldwyn Rodrigues , Shiyang Ruan , Linux Kernel Mailing List , linux-xfs , linux-nvdimm , linux-fsdevel , "Darrick J. Wong" , Jan Kara , Al Viro , Btrfs BTRFS , ocfs2-devel@oss.oracle.com, david , Christoph Hellwig Subject: Re: [PATCH v2 00/10] fsdax,xfs: Add reflink&dedupe support for fsdax Message-ID: References: <20210226002030.653855-1-ruansy.fnst@fujitsu.com> <20210310130227.GN3479805@casper.infradead.org> <20210310142159.kudk7q2ogp4yqn36@fiona> <20210310142643.GQ3479805@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Junkbait: aaron@angband.pl, zzyx@angband.pl X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: kilobyte@angband.pl X-SA-Exim-Scanned: No (on tartarus.angband.pl); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 13, 2021 at 11:24:00AM -0500, Neal Gompa wrote: > On Sat, Mar 13, 2021 at 8:09 AM Adam Borowski wrote: > > > > On Wed, Mar 10, 2021 at 02:26:43PM +0000, Matthew Wilcox wrote: > > > On Wed, Mar 10, 2021 at 08:21:59AM -0600, Goldwyn Rodrigues wrote: > > > > DAX on btrfs has been attempted[1]. Of course, we could not > > > > > > But why? A completeness fetish? I don't understand why you decided > > > to do this work. > > > > * xfs can shapshot only single files, btrfs entire subvolumes > > * btrfs-send|receive > > * enumeration of changed parts of a file > > XFS cannot do snapshots since it lacks metadata COW. XFS reflinking is > primarily for space efficiency. A reflink is a single-file snapshot. My work team really wants this very patchset -- reflinks on DAX allow backups and/or checkpointing, without stopping the world (there's a single file, "pool", here). Besides, you can still get poor-man's whole-subvolume(/directory) snapshots by manually walking the tree and reflinking everything. That's not atomic -- but rsync isn't atomic either. That's enough for eg. dnf/dpkg purposes. Meow! -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢰⠒⠀⣿⡁ ⢿⡄⠘⠷⠚⠋⠀ NADIE anticipa la inquisición de españa! ⠈⠳⣄⠀⠀⠀⠀