Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 19 Jul 2002 16:46:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 19 Jul 2002 16:46:23 -0400 Received: from h24-67-14-151.cg.shawcable.net ([24.67.14.151]:31997 "EHLO webber.adilger.int") by vger.kernel.org with ESMTP id ; Fri, 19 Jul 2002 16:46:22 -0400 From: Andreas Dilger Date: Fri, 19 Jul 2002 14:47:38 -0600 To: Shawn Cc: linux-kernel@vger.kernel.org Subject: Re: [ANNOUNCE] Ext3 vs Reiserfs benchmarks Message-ID: <20020719204738.GF10315@clusterfs.com> Mail-Followup-To: Shawn , linux-kernel@vger.kernel.org References: <20020716153926.GR7955@tahoe.alcove-fr> <20020716194542.GD22053@merlin.emma.line.org> <20020716150422.A6254@q.mn.rr.com> <20020716161158.A461@shookay.newview.com> <20020716152231.B6254@q.mn.rr.com> <20020717114501.GB28284@merlin.emma.line.org> <20020717190259.GA31503@clusterfs.com> <20020719102906.A5131@krusty.dt.e-technik.uni-dortmund.de> <20020719163907.GD10315@clusterfs.com> <20020719150116.A31973@q.mn.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020719150116.A31973@q.mn.rr.com> User-Agent: Mutt/1.3.28i X-GPG-Key: 1024D/0D35BED6 X-GPG-Fingerprint: 7A37 5D79 BF1B CECA D44F 8A29 A488 39F5 0D35 BED6 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1688 Lines: 39 On Jul 19, 2002 15:01 -0500, Shawn wrote: > On 07/19, Andreas Dilger said something like: > > You cannot mount a dirty ext3 filesystem from read-only media. > > I thought you could "mount -t ext2" ext3 volumes, and thought you could > force mount ext2. This is true if the ext3 filesystem is unmounted cleanly. Otherwise there is a flag in the superblock which tells the kernel it can't mount the filesystem because there is something there it doesn't understand (namely the dirty journal with all of the recent changes). This flag (EXT3_FEATURE_INCOMPAT_RECOVERY) is cleared when the filesystem is unmounted properly, when e2fsck or a r/w mount recovers the journal, and not coincidentally when an LVM snapshot is created. In case you are more curious, there are a couple of paragraphs in linux/Documentation/filesystems/ext2.txt about the compat flags, which are really one of the great features of ext2. You may think that an overstatement, but without the feature flags, none of the other enhancements that have been added to ext2 over the last few years (and in the next few years too) would have been so easily done. As for mounting a dirty ext2 filesystem, yes that is possible with only a warning at mount time. That is why nobody has put much effort into adding the snapshot hooks into ext2 yet. Cheers, Andreas -- Andreas Dilger http://www-mddsp.enel.ucalgary.ca/People/adilger/ http://sourceforge.net/projects/ext2resize/ - 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/