lvm+dmsetup device mapper rules

This is an attempt at generic device mapper rules file. Both lvm and
manually (dmsetup) created devices are supported. The rules file depends
only on lvm and dmsetup binaries.

Standard /dev/disk/* symlinks are created at the end, with additional
/dev/disk/by-id/dm-uuid-* symlinks (by device's uuid, not filesystem's one).

KERNEL=="device-mapper", NAME="mapper/control", GOTO="dm_end"

ACTION!="add|change", GOTO="dm_end"
SUBSYSTEM!="block", GOTO="dm_end"
KERNEL!="dm*", GOTO="dm_end"

# First get the name from dmsetup - it can be fed to lvs for parsing

PROGRAM="/sbin/dmsetup info -c --noheadings -o name -j%M -m%m", ENV{DM_NAME}="%c"
ENV{DM_NAME}!="?*", GOTO="dm_end"

ENV{DM_NAME}=="?*", NAME="mapper/$env{DM_NAME}"

# Try to get volume group name
# - lvs always indents first field with 2 spaces (thus %c{2})
# - note, that node doesn't have to exist, and it would fail if $tempnode was used

PROGRAM="/sbin/lvm lvs --ignorelockingfailure --noheadings -o vg_name
/dev/mapper/$env{DM_NAME}", ENV{LVM_VGN}="%c{2}"
ENV{LVM_VGN}!="?*", GOTO="dm_finalize"
PROGRAM="/sbin/lvm lvs --ignorelockingfailure --noheadings -o lv_name