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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,URIBL_BLOCKED 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 E5A24C432BE for ; Tue, 27 Jul 2021 15:04:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CDF0A61B03 for ; Tue, 27 Jul 2021 15:04:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232713AbhG0PEl (ORCPT ); Tue, 27 Jul 2021 11:04:41 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:43692 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231552AbhG0PEk (ORCPT ); Tue, 27 Jul 2021 11:04:40 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04395;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0UhAAkxc_1627398276; Received: from B-P7TQMD6M-0146.local(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0UhAAkxc_1627398276) by smtp.aliyun-inc.com(127.0.0.1); Tue, 27 Jul 2021 23:04:38 +0800 Date: Tue, 27 Jul 2021 23:04:36 +0800 From: Gao Xiang To: Matthew Wilcox , "Darrick J . Wong" Cc: dsterba@suse.cz, Christoph Hellwig , Andreas Gruenbacher , Huang Jianan , linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Gruenbacher Subject: Re: [PATCH v7] iomap: make inline data support more flexible Message-ID: Mail-Followup-To: Matthew Wilcox , "Darrick J . Wong" , dsterba@suse.cz, Christoph Hellwig , Andreas Gruenbacher , Huang Jianan , linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Gruenbacher References: <20210723174131.180813-1-hsiangkao@linux.alibaba.com> <20210725221639.426565-1-agruenba@redhat.com> <20210726110611.459173-1-agruenba@redhat.com> <20210726121702.GA528@lst.de> <20210727082042.GI5047@twin.jikos.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 27, 2021 at 02:35:46PM +0100, Matthew Wilcox wrote: > On Tue, Jul 27, 2021 at 10:20:42AM +0200, David Sterba wrote: > > On Mon, Jul 26, 2021 at 02:17:02PM +0200, Christoph Hellwig wrote: > > > > Subject: iomap: Support tail packing > > > > > > I can't say I like this "tail packing" language here when we have the > > > perfectly fine inline wording. Same for various comments in the actual > > > code. > > > > Yes please, don't call it tail-packing when it's an inline extent, we'll > > use that for btrfs eventually and conflating the two terms has been > > cofusing users. Except reiserfs, no linux filesystem does tail-packing. > > Hmm ... I see what reiserfs does as packing tails of multiple files into > one block. What gfs2 (and ext4) do is inline data. Erofs packs the > tail of a single file into the same block as the inode. If I understand Plus each erofs block can have multiple inodes (thus multi-tail blocks) oo as long as the meta block itself can fit. No matter what it's called, it's a kind of inline data (I think inline means that data mixes with metadata according to [1]). I was called it tail-block inline initially... whatever. Hopefully, Darrick could update the v8 title if some concern here. [1] https://www.kernel.org/doc/Documentation/filesystems/fiemap.txt Thanks, Gao Xiang > what btrfs does correctly, it stores data in the btree. But (like > gfs2/ext4), it's only for the entire-file-is-small case, not for > its-just-ten-bytes-into-the-last-block case. > > So what would you call what erofs is doing if not tail-packing? > Wikipedia calls it https://en.wikipedia.org/wiki/Block_suballocation > which doesn't quite fit. We need a phrase which means "this isn't > just for small files but for small tails of large files".