Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760589AbZADTVa (ORCPT ); Sun, 4 Jan 2009 14:21:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758594AbZADTVR (ORCPT ); Sun, 4 Jan 2009 14:21:17 -0500 Received: from monty.telenet-ops.be ([195.130.132.56]:41443 "EHLO monty.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760529AbZADTVO (ORCPT ); Sun, 4 Jan 2009 14:21:14 -0500 Date: Sun, 4 Jan 2009 20:21:06 +0100 (CET) From: Geert Uytterhoeven To: Theodore Tso cc: Duane Griffin , Valdis.Kletnieks@vt.edu, Martin =?utf-8?Q?MOKREJ=C5=A0?= , Pavel Machek , kernel list , Andrew Morton , mtk.manpages@gmail.com, rdunlap@xenotime.net, linux-doc@vger.kernel.org Subject: Re: document ext3 requirements In-Reply-To: <20090104184040.GC17558@mit.edu> Message-ID: References: <20090103222957.GG1666@elf.ucw.cz> <495FEE66.9080903@ribosome.natur.cuni.cz> <495FF9CE.2020908@ribosome.natur.cuni.cz> <495FFECB.5040001@ribosome.natur.cuni.cz> <15786.1231041158@turing-police.cc.vt.edu> <20090104184040.GC17558@mit.edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2288 Lines: 46 On Sun, 4 Jan 2009, Theodore Tso wrote: > On Sun, Jan 04, 2009 at 02:24:43PM +0000, Duane Griffin wrote: > > > Is there a way using md/dm/lvm etc to make the source partition R/O and > > > replay the journal onto a CoW snapshop? Admittedly, not easy to do inside > > > the 'mount' command itself, but at least it might be workable for LiveCD R/O > > > mounts and forensics work, where you can *tell* beforehand that's what you > > > want and can jump through setup games before doing the mount... > > > > Yes, something like that is best practice, as I understand it. The > > LiveCD init scripts could check whether they are about to R/O mount an > > ext[34] filesystem needing recovery and either refuse with a useful > > message to the user, or even automatically create and mount a COW > > snapshot, as you described. They'd still need to warn the user though, > > since things like remounting R/W wouldn't work as expected. > > So what's the use case where people want to be able to mount a > filesystem needing recovery read/only without running the journal? As mentioned before, suspending a laptop (running from hdd), running a live CD, and expecting everything to work fine when resuming from hdd? I think most people get shocked when they discover that mounting something read-only may actualy write to the media. This is a bit unexpected (hey, if I mount `read-only', I expect that no writes will happen), as it behaved differently before the introduction of journalling. As for mounting the root file system read-only during early boot up, and remounting it read-write later, I guess it's quite complicated to replay the journal (in RAM) on read-only mount, and deferring the replay writeback until remounting read-write? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- 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/