#!/usr/bin/ash

# teardown a single device by node name
#   $1: device node name, e.g. md0, dm-2
stop_device() {
    local devtype= devname=

    # the device must still be active
    [ -e "/sys/class/block/$1" ] || return 1

    # this can sometimes fail on stopped md devices, when the
    # sysfs node doesn't go away as quickly as i'd like it to.
    devtype=$(lsblk -drno TYPE "/dev/$1" 2>/dev/null) || return 1
    case $devtype in
        crypt)
            read devname <"$1/dm/name"
            cryptsetup remove "$devname"
            ;;
        dm)
            read devname <"$1/dm/name"
            dmsetup remove "$devname"
            ;;
        lvm)
            # disassemble the parent VG
            read devname <"$1/dm/name"
            lvm lvdisplay -c "/dev/mapper/$devname" | {
                IFS=: read _ vgname _
                lvm vgchange --noudevsync -an "$vgname"
            }
            ;;
        raid*)
            mdadm --stop "/dev/$1"
            ;;
        dmraid)
            read devname <"$1/dm/name"
            dmraid -an "$devname"
            ;;
        # silently ignore unstacked devices
    esac
}

# recursively disassemble a device chain
#   $1: device node name, e.g. md0, dm-2
disassemble() {
    local holder=

    for holder in "$1"/holders/*; do
        if [ ! -e "$holder" ]; then
            # end of the chain, recurse back up
            stop_device "$1"
            return
        fi
        disassemble "${holder##*/}"
        stop_device "$1"
    done
}

# XXX: Discourage libdevmapper from thinking that udev
# might be in a useful state. FS#30995.
rm -rf /run/udev

printf '%s\n' 'Detaching loop devices.'

for loop in loop*/loop; do
    [ -e "$loop" ] && losetup -d "${loop%/loop}"
done

printf '%s\n' "Unmounting all devices."

# unmount everything in /oldroot
findmnt -Rruno TARGET /oldroot | awk '
BEGIN { i = 0 }
{
    i++
    mounts[i] = $0
}
END {
    for (j = i; j > 0; j--) {
        print mounts[j]
    }
}
' | while read -r mount; do
    umount "$mount"
done

printf '%s\n' "Disassembling stacked devices."

# chdir, so that we can avoid a lot of path chopping
cd /sys/class/block

# iterate over devices with holders
for part in */holders/*; do
    [ -e "$part" ] && disassemble "${part%%/*}"
done

case $1 in
    poweroff|shutdown|halt)
        "$1" -f
        ;;
    *)
        type kexec >/dev/null && kexec -e
        reboot -f
        ;;
esac

# vim: ft=sh ts=4 sw=4