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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 18F80C04AB6 for ; Wed, 29 May 2019 02:18:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E3C6F21019 for ; Wed, 29 May 2019 02:18:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725936AbfE2CSE (ORCPT ); Tue, 28 May 2019 22:18:04 -0400 Received: from mail.cn.fujitsu.com ([183.91.158.132]:27181 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725816AbfE2CSD (ORCPT ); Tue, 28 May 2019 22:18:03 -0400 X-IronPort-AV: E=Sophos;i="5.60,525,1549900800"; d="scan'208";a="65013469" Received: from unknown (HELO cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 29 May 2019 10:18:01 +0800 Received: from G08CNEXCHPEKD01.g08.fujitsu.local (unknown [10.167.33.80]) by cn.fujitsu.com (Postfix) with ESMTP id 793AB4CDD26D; Wed, 29 May 2019 10:02:01 +0800 (CST) Received: from [10.167.225.140] (10.167.225.140) by G08CNEXCHPEKD01.g08.fujitsu.local (10.167.33.89) with Microsoft SMTP Server (TLS) id 14.3.439.0; Wed, 29 May 2019 10:02:12 +0800 Subject: Re: [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes To: Jan Kara CC: Goldwyn Rodrigues , "Darrick J. Wong" , , , , , , , , , 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> From: Shiyang Ruan Message-ID: Date: Wed, 29 May 2019 10:01:58 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190528091729.GD9607@quack2.suse.cz> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.225.140] X-yoursite-MailScanner-ID: 793AB4CDD26D.ADE41 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: ruansy.fnst@cn.fujitsu.com Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org 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 ...; } > > Honza > -- Thanks, Shiyang Ruan.