What has device mapper done to me?

[Tom Horsley <tom.horsley@ccur.com>]

I've got a debian etch system running Xen 3.2 (built from source,
so I'm using the xen kernel source).

I installed various device mapper related packages to allow me to
access the xen VM virtual disks using losetup, kpartx, etc.

Now, the next time I boot the system, fsck pukes its guts out,
there are /dev/dm-* devices exclusively using all my /dev/sd* devices,
everything is out of wack.

I temporarily fixed this by simply renaming the kernel/devices/md
directory so it couldn't find any device mapper modules, but what I
really want to do is make it stop trying to treat all my disks
as things that should be referenced through the device mapper.

What the heck is doing that? Anyone know? Can I disable some init
script or edit some config file?