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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 CB020C072B1 for ; Wed, 29 May 2019 02:47:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA3F321019 for ; Wed, 29 May 2019 02:47:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725855AbfE2Cr6 (ORCPT ); Tue, 28 May 2019 22:47:58 -0400 Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:39183 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725816AbfE2Cr6 (ORCPT ); Tue, 28 May 2019 22:47:58 -0400 Received: from dread.disaster.area (pa49-180-144-61.pa.nsw.optusnet.com.au [49.180.144.61]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id BC575D1A1; Wed, 29 May 2019 12:47:51 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92) (envelope-from ) id 1hVod3-0000Tb-MZ; Wed, 29 May 2019 12:47:49 +1000 Date: Wed, 29 May 2019 12:47:49 +1000 From: Dave Chinner To: Shiyang Ruan Cc: Jan Kara , Goldwyn Rodrigues , "Darrick J. Wong" , linux-btrfs@vger.kernel.org, kilobyte@angband.pl, linux-fsdevel@vger.kernel.org, willy@infradead.org, hch@lst.de, dsterba@suse.cz, nborisov@suse.com, linux-nvdimm@lists.01.org Subject: Re: [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes Message-ID: <20190529024749.GC16786@dread.disaster.area> References: <20190429172649.8288-1-rgoldwyn@suse.de> <20190429172649.8288-5-rgoldwyn@suse.de> <20190521165158.GB5125@magnolia> <1e9951c1-d320-e480-3130-dc1f4b81ef2c@cn.fujitsu.com> <20190523115109.2o4txdjq2ft7fzzc@fiona> <1620c513-4ce2-84b0-33dc-2675246183ea@cn.fujitsu.com> <20190528091729.GD9607@quack2.suse.cz> 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=FNpr/6gs c=1 sm=1 tr=0 cx=a_idp_d a=8RU0RCro9O0HS2ezTvitPg==:117 a=8RU0RCro9O0HS2ezTvitPg==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=E5NmQfObTbMA:10 a=7-415B0cAAAA:8 a=XyvwrCn6JVpaNVbEGqAA:9 a=vEUpTPDqILtuVklf:21 a=ZaHK-JVdKnvBLsfL:21 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, May 29, 2019 at 10:01:58AM +0800, Shiyang Ruan wrote: > > On 5/28/19 5:17 PM, Jan Kara wrote: > > On Mon 27-05-19 16:25:41, Shiyang Ruan wrote: > > > On 5/23/19 7:51 PM, Goldwyn Rodrigues wrote: > > > > > > > > > > Hi, > > > > > > > > > > I'm working on reflink & dax in XFS, here are some thoughts on this: > > > > > > > > > > As mentioned above: the second iomap's offset and length must match the > > > > > first. I thought so at the beginning, but later found that the only > > > > > difference between these two iomaps is @addr. So, what about adding a > > > > > @saddr, which means the source address of COW extent, into the struct iomap. > > > > > The ->iomap_begin() fills @saddr if the extent is COW, and 0 if not. Then > > > > > handle this @saddr in each ->actor(). No more modifications in other > > > > > functions. > > > > > > > > Yes, I started of with the exact idea before being recommended this by Dave. > > > > I used two fields instead of one namely cow_pos and cow_addr which defined > > > > the source details. I had put it as a iomap flag as opposed to a type > > > > which of course did not appeal well. > > > > > > > > We may want to use iomaps for cases where two inodes are involved. > > > > An example of the other scenario where offset may be different is file > > > > comparison for dedup: vfs_dedup_file_range_compare(). However, it would > > > > need two inodes in iomap as well. > > > > > > > Yes, it is reasonable. Thanks for your explanation. > > > > > > One more thing RFC: > > > I'd like to add an end-io callback argument in ->dax_iomap_actor() to update > > > the metadata after one whole COW operation is completed. The end-io can > > > also be called in ->iomap_end(). But one COW operation may call > > > ->iomap_apply() many times, and so does the end-io. Thus, I think it would > > > be nice to move it to the bottom of ->dax_iomap_actor(), called just once in > > > each COW operation. > > > > I'm sorry but I don't follow what you suggest. One COW operation is a call > > to dax_iomap_rw(), isn't it? That may call iomap_apply() several times, > > each invocation calls ->iomap_begin(), ->actor() (dax_iomap_actor()), > > ->iomap_end() once. So I don't see a difference between doing something in > > ->actor() and ->iomap_end() (besides the passed arguments but that does not > > seem to be your concern). So what do you exactly want to do? > > Hi Jan, > > Thanks for pointing out, and I'm sorry for my mistake. It's > ->dax_iomap_rw(), not ->dax_iomap_actor(). > > I want to call the callback function at the end of ->dax_iomap_rw(). > > Like this: > dax_iomap_rw(..., callback) { > > ... > while (...) { > iomap_apply(...); > } > > if (callback != null) { > callback(); > } > return ...; > } Why does this need to be in dax_iomap_rw()? We already do post-dax_iomap_rw() "io-end callbacks" directly in xfs_file_dax_write() to update the file size.... Cheers, Dave. -- Dave Chinner david@fromorbit.com