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=-7.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 5A183C4338F for ; Tue, 27 Jul 2021 16:56:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2CF0060FF0 for ; Tue, 27 Jul 2021 16:56:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229687AbhG0Q4E (ORCPT ); Tue, 27 Jul 2021 12:56:04 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:48726 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229453AbhG0Q4D (ORCPT ); Tue, 27 Jul 2021 12:56:03 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 0F3F7221EC; Tue, 27 Jul 2021 16:56:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1627404962; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=I6xqCcuCxJ3dCYSStp64lbp+Ddy6J/xCqtuiJjo0KTU=; b=l9VZZdmXPaqiSYtXX46V49UfixDqIhSkECPLTwTkbtGHLK/AuoKm06q7J3PS373yKVmts2 O1lrA2stloOZxxU5jN7bq00RpFLddcX2uIIN2fAnKqONgUg6hYoAmUfTEaUA9iBQ+j2HGk owdkUrtd1KN7PW2qSLuwBHp7oGC/vIE= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1627404962; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=I6xqCcuCxJ3dCYSStp64lbp+Ddy6J/xCqtuiJjo0KTU=; b=tZv5ZZHUElMD+oEJaRkN3pa6JgcLy1DGjYM+xi/S88Md/OALdTnSju1j/wKZw93J67fkLj H4rY+l0mcJfK1wBw== Received: from ds.suse.cz (ds.suse.cz [10.100.12.205]) by relay2.suse.de (Postfix) with ESMTP id 81D68A3B81; Tue, 27 Jul 2021 16:56:01 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id EBA30DA8D6; Tue, 27 Jul 2021 18:53:16 +0200 (CEST) Date: Tue, 27 Jul 2021 18:53:16 +0200 From: David Sterba To: Matthew Wilcox Cc: Christoph Hellwig , Andreas Gruenbacher , Gao Xiang , "Darrick J . Wong" , 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: <20210727165315.GU5047@suse.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Matthew Wilcox , Christoph Hellwig , Andreas Gruenbacher , Gao Xiang , "Darrick J . Wong" , 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=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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 > 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? That indeed sounds like tail-packing and I was not aware of that, the docs I found were not clear what exactly was going on with the data stored inline. > 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". So that's more generic than what we now have as inline files, so in the interface everybody sets 0 as start of the range while erofs can also set start of the last partial block.