mdadm+lvm2: ioctl error and cannot mount the device nodes?

[Michael Ole Olsen <gnu@gmx.net>]

i keep getting

[1]
device-mapper: table: device 9:0 too small for target
device-mapper: table: 254:11: linear: dm-linear: Device lookup failed
device-mapper: ioctl: error adding target to table

with a cleanly installed system (debian lenny netinstall)

my raid is a raid5 reshaped to raid6 with 2.6.30 by echoing into /sys
(all Q blocks on the last disk)

i can see all device nodes in /dev/mapper but just not mount them

if i try to mount it just says:
    mount: you must specify the filesystem type
and the dmesg output as in [1]

these are the modules in my initramfs:

xfs
ext3
dm-mod
md
raid0
raid1
raid10
raid456
raid6_pq
linear

# usb-storage deps
usbcore
usbhid
libata
scsi_transport_spi
usb-storage
scsi_mod
sg
sd_mod
sbp2


Any idea what I am doing wrong? I thought the problem [1] would
be because of a misconfigured kernel with no
devicemapper support, but I think have compiled everything in?

I cannot use any other kernels than 2.6.30 or it will not assemble
the raid6 (mdadm) so I dont think i have another option than
compiling it myself, apt has only 2.6.22 or such