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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY 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 0B31CC07E9B for ; Wed, 21 Jul 2021 02:55:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D6C2B61019 for ; Wed, 21 Jul 2021 02:55:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231367AbhGUCN7 (ORCPT ); Tue, 20 Jul 2021 22:13:59 -0400 Received: from out4436.biz.mail.alibaba.com ([47.88.44.36]:44349 "EHLO out4436.biz.mail.alibaba.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229903AbhGUCNf (ORCPT ); Tue, 20 Jul 2021 22:13:35 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R991e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0UgTuycl_1626836038; Received: from B-P7TQMD6M-0146.local(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0UgTuycl_1626836038) by smtp.aliyun-inc.com(127.0.0.1); Wed, 21 Jul 2021 10:53:59 +0800 Date: Wed, 21 Jul 2021 10:53:58 +0800 From: Gao Xiang To: Andreas =?utf-8?Q?Gr=C3=BCnbacher?= Cc: "Darrick J. Wong" , Matthew Wilcox , linux-erofs@lists.ozlabs.org, Linux FS-devel Mailing List , LKML , Christoph Hellwig Subject: Re: [PATCH v4] iomap: support tail packing inline read Message-ID: Mail-Followup-To: Andreas =?utf-8?Q?Gr=C3=BCnbacher?= , "Darrick J. Wong" , Matthew Wilcox , linux-erofs@lists.ozlabs.org, Linux FS-devel Mailing List , LKML , Christoph Hellwig References: <20210720133554.44058-1-hsiangkao@linux.alibaba.com> <20210720204224.GK23236@magnolia> <20210721001720.GS22357@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andreas, On Wed, Jul 21, 2021 at 04:26:47AM +0200, Andreas Grünbacher wrote: > Am Mi., 21. Juli 2021 um 02:33 Uhr schrieb Gao Xiang > : > > > And since you can only kmap one page at a time, an inline read grabs the > > > first part of the data in "page one" and then we have to call > > > iomap_begin a second time get a new address so that we can read the rest > > > from "page two"? > > > > Nope, currently EROFS inline data won't cross page like this. > > > > But in principle, yes, I don't want to limit it to the current > > EROFS or gfs2 usage. I think we could make this iomap function > > more generally (I mean, I'd like to make the INLINE extent > > functionity as general as possible, > > Nono. Can we please limit this patch what we actually need right now, > and worry about extending it later? Can you elaborate what it will benefit us if we only support one tail block for iomap_read_inline_data()? (I mean it has similar LOC changes, similar implementation / complexity.) The only concern I think is if it causes gfs2 regression, so that is what I'd like to confirm. In contrast, I'd like to avoid iomap_write_begin() tail-packing because it's complex and no fs user interests in it for now. So I leave it untouched for now. Another concern I really like to convert EROFS to iomap is I'd like to support sub-page blocksize for EROFS after converting. I don't want to touch iomap inline code again like this since it interacts 2 directories thus cause too much coupling. Thanks, Gao Xiang > > > my v1 original approach > > in principle can support any inline extent in the middle of > > file rather than just tail blocks, but zeroing out post-EOF > > needs another iteration) and I don't see it add more code and > > complexity. > > Thanks, > Andreas