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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 7FB12C43215 for ; Thu, 14 Nov 2019 20:24:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 66A862070E for ; Thu, 14 Nov 2019 20:24:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726852AbfKNUYJ (ORCPT ); Thu, 14 Nov 2019 15:24:09 -0500 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:54791 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726474AbfKNUYJ (ORCPT ); Thu, 14 Nov 2019 15:24:09 -0500 Received: from dread.disaster.area (pa49-181-255-80.pa.nsw.optusnet.com.au [49.181.255.80]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 3D5E743E7D2; Fri, 15 Nov 2019 07:24:04 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1iVLer-0002xv-KL; Fri, 15 Nov 2019 07:24:01 +1100 Date: Fri, 15 Nov 2019 07:24:01 +1100 From: Dave Chinner To: Dan Williams Cc: Shiyang Ruan , linux-xfs , linux-nvdimm , "Darrick J. Wong" , Goldwyn Rodrigues , Christoph Hellwig , Linux Kernel Mailing List , gujx@cn.fujitsu.com, qi.fuli@fujitsu.com Subject: Re: [RFC PATCH v2 0/7] xfs: reflink & dedupe for fsdax (read/write path). Message-ID: <20191114202401.GB4614@dread.disaster.area> References: <20191030041358.14450-1-ruansy.fnst@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=G6BsK5s5 c=1 sm=1 tr=0 a=XqaD5fcB6dAc7xyKljs8OA==:117 a=XqaD5fcB6dAc7xyKljs8OA==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=MeAgGD-zjQ4A:10 a=omOdbC7AAAAA:8 a=7-415B0cAAAA:8 a=LDxVRJNMUMF_87RH2osA:9 a=CjuIK1q_8ugA:10 a=baC4JDFNLZpnPwus_NF9:22 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 07, 2019 at 07:30:32PM -0800, Dan Williams wrote: > On Thu, Nov 7, 2019 at 7:11 PM Shiyang Ruan wrote: > > > > Hi Darrick, Dave, > > > > Do you have any comment on this? > > Christoph pointed out at ALPSS that this problem has significant > overlap with the shared page-cache for reflink problem. So I think we > need to solve that first and then circle back to dax reflink support. > I'm starting to take a look at that. I think the DAX side is somewhat simpler because it doesn't really need to involve the page cache and we don't have to worry about subtly breaking random filesystems. Hence I'd suggest we sort out a solution for DAX first, then worry about page cache stuff. The shared page cache for reflink feature is not a show stopper - multiple references for DAX is a show stopper. Let's deal with the DAX problem first. Cheers, -Dave. -- Dave Chinner david@fromorbit.com