From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 24 Sep 2001 01:19:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 24 Sep 2001 01:19:07 -0400 Received: from vasquez.zip.com.au ([203.12.97.41]:43533 "EHLO vasquez.zip.com.au") by vger.kernel.org with ESMTP id ; Mon, 24 Sep 2001 01:18:55 -0400 Message-ID: <3BAEC254.2A29B495@zip.com.au> Date: Sun, 23 Sep 2001 22:19:16 -0700 From: Andrew Morton X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-ac12 i686) X-Accept-Language: en MIME-Version: 1.0 To: Aaron Lehmann CC: linux-kernel@vger.kernel.org Subject: Re: Linux-2.4.10 + ext3 In-Reply-To: <1001280620.3540.33.camel@gromit.house> <9om4ed$1hv$1@penguin.transmeta.com>, <9om4ed$1hv$1@penguin.transmeta.com> <20010923193008.A13982@vitelus.com> <3BAEAC52.677C064C@zip.com.au>, <3BAEAC52.677C064C@zip.com.au> <20010923214507.A15014@vitelus.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Aaron Lehmann wrote: > > ... > I simply was hoping for insted of: > > <*> EXT2 fs > <*> EXT3 fs > > (which is required today for most ext3-using people who want to do ext2 > mounts) > > ... there could be: > > <*> EXT2 fs > <*> EXT3 journalling extensions > > AFAIK this would eliminate a lot of duplicate kernel code for ext3 > users. > mm.. The filesystems could be pretty much identical on the reading path, but they're quite dissimilar on the writing path. So the reading-stuff code could be commoned up. I don't think it'd buy much, though. They are different filesystems and the fact that ext3 borrows a lot of ext2 code is a useful consequence of it having the same on-disk format. And the main reason for having the same on-disk format is not, IMO, to ease migration between the two filesystems. That's just a once-off activity. The main reason for preserving compatibility is so that ext3 can leverage e2fsprogs, and the wealth of knowledge and understanding of ext2 performance and behaviour. The ext2-compatibility seems to be a bit of a political albatross for ext3, really - people appear to be of the opinion that the ext3 design was somehow compromised by the compatibility requirement. This isn't so - ext3 is a block-level journalled filesystem. It could have been based on minixfs, UFS, sysvfs, etc. Or it could have been something altogether new. But I can't think of any benefit in changing the on-disk format from its current ext2ness. -