linuxgeek: [nslu2-linux] Unusual trouble with loop.o

Hi guys,

this does not happen very often, but I've run out of ideas.

I am trying to mount an ext3 image via a loop device on
unslung-6.10beta. Nothing fancy, I do that every day on my other linux
boxes.

1.) ipkg install kernel-module-loop

2.) insmod loop

3.) dmesg | tail
EXT3 FS 2.4-0.9.19, 19 August 2002 on sd(8,2), internal journal
EXT3-fs: recovery complete.
EXT3-fs: mounted filesystem with ordered data mode.
Adding Swap: 120476k swap-space (priority -1)
loop: loaded (max 8 devices)

4.) lsmod
Module Size Used by Tainted: P
loop 8896 0
[...]

5.) mount /test.ext3 /mnt/backup -o loop
mount: cannot setup loop device

6.) strace mount /test.ext3 /mnt/backup -o loop

[...]
lstat64("/test.ext3", {st_mode=S_IFREG|0600, st_size=104857600, ...}) = 0
open("/test.ext3", O_RDWR|O_LARGEFILE) = 3
stat64("/dev/loop0", {st_mode=S_IFBLK|0600, st_rdev=makedev(0, 0), ...}) = 0
open("/dev/loop0", O_RDWR|O_LARGEFILE) = 4
ioctl(4, 0x4c05, 0xbffff7f4) = -1 EINVAL (Invalid argument)
close(4) = 0
[...]

-bash-3.2# ls -la /dev/loop0
brw------- 1 root root 7, 0 Mar 21 18:22 /dev/loop0

Now I've seen many issues with loop devices: Wrong block device
properties, wrong/no kernel module, ... but I have never seen "ioctl
0x4c05" (LOOP_GET_STATUS64) failing.

Does anybody have a clue what issue I might be facing here or how I can
debug it further? Google doesn't know anything, so that I am tempted to
migrate to Debian/NSLU2 because this issue is a blocker for my backup
project. But I refuse to give up ;-)

Thanks for any inspiration.

--Thomas