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 21:32:21 -0800 Message-ID: <4EB76D65.7070509@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> <4EB76C21.5060104@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]:42735 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752417Ab1KGDdO (ORCPT ); Sun, 6 Nov 2011 22:33:14 -0500 Received: by iage36 with SMTP id e36so5362645iag.19 for ; Sun, 06 Nov 2011 19:33:13 -0800 (PST) In-Reply-To: <4EB76C21.5060104@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 11/06/2011 09:26 PM, Matt Parnell wrote: > 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. That is, you were right in removing rootflags=data=writeback from the kernel boot params, and removing data=writeback from fstab would fix it - that commit is where things break, though... So really instead of breaking it should log that it's ignoring that flag becuase it's enabled by default when there's no journal.