Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754595AbZAJSNu (ORCPT ); Sat, 10 Jan 2009 13:13:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752661AbZAJSNk (ORCPT ); Sat, 10 Jan 2009 13:13:40 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:42620 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752127AbZAJSNj (ORCPT ); Sat, 10 Jan 2009 13:13:39 -0500 Date: Sat, 10 Jan 2009 10:12:35 -0800 From: Andrew Morton To: =?ISO-8859-1?Q?J=F6rn?= Engel Cc: Ingo Molnar , David Brown , Phil Oester , Kay Sievers , Phillip Lougher , Christoph Hellwig , torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [GIT PULL] Squashfs pull request for 2.6.29 Message-Id: <20090110101235.7ca24c44.akpm@linux-foundation.org> In-Reply-To: <20090110165033.GA23943@logfs.org> References: <20090108165029.GA10951@infradead.org> <20090108175338.2abbee16.akpm@linux-foundation.org> <4966B24E.1050700@lougher.demon.co.uk> <20090109023629.GA29520@linuxace.com> <20090109165422.GF24884@logfs.org> <20090109193738.GA9827@linode.davidb.org> <20090109211937.GA14342@logfs.org> <20090110124335.GB30744@elte.hu> <20090110165033.GA23943@logfs.org> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1086 Lines: 28 On Sat, 10 Jan 2009 17:50:33 +0100 J__rn Engel wrote: > What is the thing that makes a read only > filesystem special? Nothing, really. The filesystem has mount options (I think). That interface needs to be maintained. More importantly, the filesystem driver has to be able to read older filesystem instances. This is a userspace-visible binary interface! A really complex one. If for some reason we wish to change the on-disk format then that could be done now. But once the code is merged, such changes could only be done in a back-compatible way. And the day-one code (ie: this code) would need to be designed so that such on-disk changes can be made - we don't want old kernels exploding when asked to read new-layout filesystem instances. This is what `grep -i compat include/linux/ext2_fs.h' is all about. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/