PROBLEM: GPT partition table + RAID: kernel could not load init while root filesystem is mounted

[manio <manio@skyboo.net>]

Hello
I am trying to migrate from old root filesystem (linux raid1 on disks 
with msdos partition table) to new (4K sector) disks with GPT partition 
table (also raid1). I am using raid autodetection (i have superblock 
v0.90 on all raid devices) and i am passing /dev/mdX as a root device to 
the kernel. When i am passing root=/dev/md10 (old disks with msdos 
partition tables) booting process is fine (i am pasting relevant info):

[    6.695241] raid1: raid set md10 active with 2 out of 2 mirrors
[    6.695280] md10: detected capacity change from 0 to 6999572480
[    6.695332] md: ... autorun DONE.
[    6.695407]  md10: unknown partition table
[    6.696236] EXT3-fs (md10): error: couldn't mount because of 
unsupported optional features (240)
[    6.696508] EXT2-fs (md10): error: couldn't mount because of 
unsupported optional features (240)
[    6.743086] EXT4-fs (md10): mounted filesystem with ordered data mode
[    6.743185] VFS: Mounted root (ext4 filesystem) readonly on device 9:10.
[    6.743227] Freeing unused kernel memory: 424k freed
..... now comes INIT - and it boots correctly

BUT (!) the problem is when i am trying to pass root=/dev/md0 (raid1 on 
new disks with GPT partition tables). Then it seems like kernel cannot 
run /sbin/init from my ext4 root partition. The root filesystem seems to 
be mounted OK:

md: ... autorun DONE.
  md0: unknown partition table
EXT3-fs (md0): error: couldn't mount because of unsupported optional 
features (240)
EXT2-fs (md0): error: couldn't mount because of unsupported optional 
features (240)
EXT4-fs (md0): mounted filesystem with ordered data mode
VFS: Mounted root (ext4 filesystem) readonly on device 9:0.
Freeing unused kernel memory: 424k freed

..... now there is some USB init debug info and it stop :(
/sbin/init is not launched and it seems like the kernel hung :(
i was waiting several minutes then - and nothing happend.

If you would like to see how the boot process look like from the grub to 
the kernel hung (filmed with my digital camera) then download this:
http://manio.skyboo.net/kernel-gpt-init-problem.avi

please help me - any tips are welcome

best regards,
-- 
Mariusz Bialonczyk
jabber/e-mail: manio@skyboo.net
http://manio.skyboo.net