Re: Unable to use ext4 as root fs

[Eric Sandeen <sandeen@redhat.com>]

Stas Sergeev wrote:
> Hi.
> 
> I am trying to move my PC from
> ext3 to ext4, and so far I can't
> get it to boot. I am getting this:
> ---
> EXT3-fs: sda3: couldn't mount because of unsupported optional features 
> (240).
> ---

Depending on your distribution, you may need to fix /etc/fstab to 
reflect ext4 as the fs type, or remake your initrd/initramfs - something 
in your boot process is trying to mount it explicitly as ext3 ("-o 
ext3"), which will of course fail.

-Eric

> Google reveals that this is normal,
> and the next thing would be the
> ext4 mount, but this doesn't happen.
> The current git kernel just locks
> up tight after that message. NMI
> watchdog doesn't do anything. The
> Fedora kernel doesn't lock up, the
> keyboard works, you can Ctrl-Alt-Del,
> but nothing happens, ext4 does not
> mount.
> I know that ext4 support is compilled
> in (builtin, not a module), because
> this very kernel mounts ext4 fine
> if I boot from ext3 root fs.
> Now, with the lack of the usual
> "unable to mount root, kernel panic",
> I am starting to suspect a bug somewhere.
> Can someone please give me the hint
> about what have to be done to boot
> from ext4? Or, in case there is nothing
> special to do, where should I start
> sticking printk's to get that somehow
> debugged?
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