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, 13 Aug 2001 14:17:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 13 Aug 2001 14:17:09 -0400 Received: from h24-64-71-161.cg.shawcable.net ([24.64.71.161]:24047 "EHLO webber.adilger.int") by vger.kernel.org with ESMTP id ; Mon, 13 Aug 2001 14:17:00 -0400 From: Andreas Dilger Message-Id: <200108131815.f7DIFigl003620@webber.adilger.int> Subject: Re: ext3-2.4-0.9.6 In-Reply-To: <3B75E9E3.FAAF05CC@zip.com.au> "from Andrew Morton at Aug 11, 2001 07:28:51 pm" To: Andrew Morton Date: Mon, 13 Aug 2001 12:15:44 -0600 (MDT) CC: Tom Rini , ext3-users@redhat.com, lkml X-Mailer: ELM [version 2.4ME+ PL87 (25)] MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew writes: > I *think* that at present an unrecovered ext3 filesystem is "incomaptible" > with ext2. If, however we were to make it "read-only compatible" then > ext2-aware loaders would still be able to read the fs and boot from it. > But this stuff makes my head hurt - let's see what Andreas and Stephen > have to say. I advocated changing the compat flag to be RO_COMPAT at one time as well. Technically, an unrecovered ext3 filesystem is as "compatible" as an ext2 filesystem that was not fscked before mount. We ro mount unchecked root filesystems all the time, so there shouldn't be a _huge_ issue for ro mounting unrecovered ext3 filesystems. Stephen and Ted disagree, because with the ext3 journal it is possible to have a large number of pending changes in the journal at the time of a crash. The Linux VFS doesn't easily allow flushing all of the cached inodes between recovery and remount-rw, so this may cause filesystem corruption if the in-kernel inode data does not match the on-disk inode data after recovery. The only time this becomes an issue is with the root filesystem, generally. The "solution" for the problem at hand would probably be to make GRUB, et. al., recognize the INCOMPAT_RECOVER flag, and still read the kernel/initrd images from disk. They will generally be static, so the contents of the journal will not affect them, and can be ignored. Cheers, Andreas -- Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto, \ would they cancel out, leaving him still hungry?" http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert