From: Matt Parnell Subject: Re: Bug In ext4 in kernels > 2.6.39 - Not mounting with arguments/options I specify in fstab on root remount Date: Sun, 06 Nov 2011 21:26:57 -0800 Message-ID: <4EB76C21.5060104@gmail.com> References: <4E6F1B49.3010803@gmail.com> <4E6F6D89.5040905@redhat.com> <20111009234433.GU7948@thunk.org> <4EA0E72D.8020305@gmail.com> <20111022050031.GC4196@thunk.org> <4EA27607.20407@gmail.com> <20111022093218.GF4196@thunk.org> <4EB7416A.7080006@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , linux-ext4@vger.kernel.org To: Ted Ts'o Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:54366 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751414Ab1KGD1t (ORCPT ); Sun, 6 Nov 2011 22:27:49 -0500 Received: by iage36 with SMTP id e36so5358448iag.19 for ; Sun, 06 Nov 2011 19:27:49 -0800 (PST) In-Reply-To: <4EB7416A.7080006@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 11/06/2011 06:24 PM, Matt Parnell wrote: > On 10/22/2011 02:32 AM, Ted Ts'o wrote: >> On Sat, Oct 22, 2011 at 02:51:35AM -0500, Matt Parnell wrote: >>> That doesn't really help me at all, it's not >>> rootflags=data=writeback causing this, it's starting to make me >>> think that arch's init may be to blame, although I previously ruled >>> it out... >> Well, it looks like rootflags=data=writeback is not making it to the >> file system. That's why it's not showing up in /proc/mounts, from you >> showed us. Can you look at the kernel dmesg? >> >> You should see something like this: >> >> [ 1.421146] EXT3-fs (vda): error: couldn't mount because of >> unsupported optional features (240) >> [ 1.434057] EXT4-fs (vda): couldn't mount as ext2 due to feature >> incompatibilities >> [ 1.454631] EXT4-fs (vda): mounted filesystem with writeback data >> mode. Opts: data=writeback >> [ 1.455966] VFS: Mounted root (ext4 filesystem) readonly on device >> 254:0. >> >> >> The first line is the failure to mount the root file system as ext3. >> The 2nd is the failure to mount the file system as ext2, using the >> ext4 file system driver. The last two lines show the options show the >> mount as ext4. >> >> What do those two lines look to you. If you don't see "Opts: >> data=writeback", then somehow the rootflags option isn't getting passed >> down to the file system. Then when you try to remount the file system >> read/write, the fact that you have "data=writeback" in your /etc/fstab >> causes the failure to remount. >> >> If you simply remove that from /etc/fstab, things should work better. >> The remount will preserve whatever data=journalling mode was in use >> when the root file system was originallymounted as. If rootflags is >> non-functional, then the file system won't be mounted as >> data=writeback, but at least the boot sequence will continue without >> blowing out. >> >> - Ted > Looks like the kernel isn't creating the /dev/root link/block device, > either all of the time or some of the time, I'm confused. I figured it out. data=writeback isn't needed and is done by default if there's no journal, as per commit 373cd5c53d5ea6622c319ecd84e29e2737d488bd http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=373cd5c53d5ea6622c319ecd84e29e2737d488bd ...sorry about throwing you guys through loops over this, although I'm guessing there's still a bug in that the kernel should just warn the user about the option when it's used and otherwise ignore it instead of breaking if there's no journal.