Unable to use ext4 as root fs

Unable to use ext4 as root fs

[Stas Sergeev]

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).
---

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?

Re: Unable to use ext4 as root fs

[Eric Sandeen]

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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Re: Unable to use ext4 as root fs

[Stas Sergeev]

02.11.2009 04:49, Eric Sandeen wrote:
>> ---
>> 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.
Thanks Eric, rebuilding initrd worked!
It is still quite annoying that something
in the initrd makes the latest git kernel
to lock up hard after the mount failure
(and not for the Fedora kernel), but this
is probably unrelated to ext4...
Thanks for your help!