From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id E6A2A212746D2 for ; Tue, 28 May 2019 02:17:32 -0700 (PDT) Date: Tue, 28 May 2019 11:17:29 +0200 From: Jan Kara Subject: Re: [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes Message-ID: <20190528091729.GD9607@quack2.suse.cz> 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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1620c513-4ce2-84b0-33dc-2675246183ea@cn.fujitsu.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Shiyang Ruan Cc: kilobyte@angband.pl, jack@suse.cz, "Darrick J. Wong" , nborisov@suse.com, Goldwyn Rodrigues , 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 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? Honza -- Jan Kara SUSE Labs, CR _______________________________________________ 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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 D68D1C04AB6 for ; Tue, 28 May 2019 09:17:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B09E7208C3 for ; Tue, 28 May 2019 09:17:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726599AbfE1JRc (ORCPT ); Tue, 28 May 2019 05:17:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:47768 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725943AbfE1JRb (ORCPT ); Tue, 28 May 2019 05:17:31 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 5C7C7AFE1; Tue, 28 May 2019 09:17:30 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B0BBE1E3F53; Tue, 28 May 2019 11:17:29 +0200 (CEST) Date: Tue, 28 May 2019 11:17:29 +0200 From: Jan Kara To: Shiyang Ruan Cc: Goldwyn Rodrigues , "Darrick J. Wong" , linux-btrfs@vger.kernel.org, kilobyte@angband.pl, linux-fsdevel@vger.kernel.org, jack@suse.cz, david@fromorbit.com, 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: <20190528091729.GD9607@quack2.suse.cz> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1620c513-4ce2-84b0-33dc-2675246183ea@cn.fujitsu.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org 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? Honza -- Jan Kara SUSE Labs, CR