From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from heian.cn.fujitsu.com (mail.cn.fujitsu.com [183.91.158.132]) by ml01.01.org (Postfix) with ESMTP id DABBC21A07095 for ; Mon, 27 May 2019 01:25:47 -0700 (PDT) Subject: Re: [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes 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> From: Shiyang Ruan Message-ID: <1620c513-4ce2-84b0-33dc-2675246183ea@cn.fujitsu.com> Date: Mon, 27 May 2019 16:25:41 +0800 MIME-Version: 1.0 In-Reply-To: <20190523115109.2o4txdjq2ft7fzzc@fiona> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Goldwyn Rodrigues Cc: kilobyte@angband.pl, jack@suse.cz, "Darrick J. Wong" , nborisov@suse.com, linux-nvdimm@lists.01.org, david@fromorbit.com, dsterba@suse.cz, willy@infradead.org, linux-fsdevel@vger.kernel.org, hch@lst.de, linux-btrfs@vger.kernel.org List-ID: 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. -- Thanks, Shiyang Ruan. >> >> My RFC patchset[1] is implemented in this way and works for me, though it is >> far away from perfectness. >> >> [1]: https://patchwork.kernel.org/cover/10904307/ >> > _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm 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 C7E7CC07542 for ; Mon, 27 May 2019 08:25:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A09D32075B for ; Mon, 27 May 2019 08:25:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726504AbfE0IZr (ORCPT ); Mon, 27 May 2019 04:25:47 -0400 Received: from mail.cn.fujitsu.com ([183.91.158.132]:41803 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726185AbfE0IZr (ORCPT ); Mon, 27 May 2019 04:25:47 -0400 X-IronPort-AV: E=Sophos;i="5.60,518,1549900800"; d="scan'208";a="64781563" Received: from unknown (HELO cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 27 May 2019 16:25:45 +0800 Received: from G08CNEXCHPEKD01.g08.fujitsu.local (unknown [10.167.33.80]) by cn.fujitsu.com (Postfix) with ESMTP id 409F74C4BB7D; Mon, 27 May 2019 16:25:46 +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; Mon, 27 May 2019 16:25:52 +0800 Subject: Re: [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes To: Goldwyn Rodrigues CC: "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> From: Shiyang Ruan Message-ID: <1620c513-4ce2-84b0-33dc-2675246183ea@cn.fujitsu.com> Date: Mon, 27 May 2019 16:25:41 +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: <20190523115109.2o4txdjq2ft7fzzc@fiona> 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: 409F74C4BB7D.AD8B2 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 5/23/19 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. -- Thanks, Shiyang Ruan. >> >> My RFC patchset[1] is implemented in this way and works for me, though it is >> far away from perfectness. >> >> [1]: https://patchwork.kernel.org/cover/10904307/ >> >