* grub-core/kern/emu/getroot.c (grub_find_device): Recognize
dir == /dev/mapper.
(grub_guess_root_device): Use already known os_dev if possible.
* grub-core/kern/emu/hostdisk.c
(convert_system_partition_to_system_disk): Scan only in /dev/mapper
if device is known to be a dm one.
Also-By: Colin Watson <cjwatson@ubuntu.com>