#!/usr/bin/env bash

# Originally from: http://devresources.linux-foundation.org/dev/fumount/script/fumount
# TODO: accept either dir or device on command line (like umount does)
#           ie: /mnt/tmp or /dev/hda6
# TODO: accept relative dirs
#           ie: cd /mnt; fumount tmp

declare -rx SCRIPT=${0##*/}
declare -rx VERSION=001

if [ `whoami` != "root" ]; then
    echo "You must run this as root"
    exit 1
fi

# display script usage, then exit
function usage {
    printf "usage: $SCRIPT [-i] [-v] dir\n" >&2
    printf "  -i : interactive mode\n" >&2
    printf "  -v : verbose\n" >&2

    success=1   # don't print failure message
    exit 1
}

# print verbose/debug information
function debug {
    if [ -n "$verbose" ]; then
        printf "$1"
    fi
}

# umount was a success
function success {
    success=1
    debug "$mntpoint unmounted\n"
    exit 0
}

function on_exit {
    if [ -z "$success" ]; then
        printf "unmount failed\n" >&2
    fi
}

trap on_exit EXIT

# parse the arguments
while [ -n "$1" ]; do
    case $1 in
    -i)
        interactive=1
        ;;
    -v)
        verbose=1
        ;;
    -*)
        usage
        ;;
    *)
        if [ -z "$mntpoint" ]; then
            mntpoint=$1
        else
            usage
        fi
        ;;
    esac

    shift
done

if [ -z "$mntpoint" ]; then
    usage
fi

# strip trailing slash from mntpoint
# surely there must be a better way to do this...
while [ "`echo "$mntpoint" |grep '/$'`" ]; do
    mntpoint=${mntpoint%/}
done

# attempt a regular umount
tryumount=`umount $mntpoint 2>&1`
ret=$?
if [ "`echo $tryumount |grep 'not mounted'`" ]; then
    printf "%s is not mounted\n" "$mntpoint" >&2
    if [ -e "$mntpoint" ]; then
        printf "You must provide the full path (ie: /mnt/tmp)\n" >&2
    fi

    exit 1
fi

if [ "`echo $tryumount |grep 'not found'`" ]; then
    printf "%s not fount\n" "$mntpoint" >&2
    exit 1
fi

# did the umount succeed?
if [ $ret -eq 0 ]; then
    success
else
    # if the filesystem is busy, kill all processes accessing it
    if [ "`echo $tryumount |grep 'busy'`" ]; then
        debug "busy... killing all processes accessing the filesystem\n"

        if [ "$interactive" ]; then
            fuser -ki $mntpoint
        else
            fuser -k $mntpoint &> /dev/null
        fi
    else
        printf "%s failed... umount returned %d\n" "$SCRIPT" "$ret" >&2
        exit 1
    fi
fi

# try to umount again
tryumount=`umount $mntpoint 2>&1`
ret=$?
if [ $ret -eq 0 ]; then
    success
else
    if [ "`echo $tryumount | grep 'busy'`" ]; then

        # get the name of the device that is mounted
        exec 6<&0   # save stdin... better way to do this?
        exec < /proc/mounts
        while read line; do
            mnt=`echo $line |awk '{print $2}'`
            if [ "$mnt" = "$mntpoint" ]; then
                device=`echo $line |awk '{print $1}'`
                break
            fi
        done
        exec 0<&6 6<&-  # restore stdin

        # our first attempt didn't work, do lazy umount to make it easier
        debug "still busy, doing lazy umount\n"

        if [ "$interactive" ]; then
            printf "Do a lazy unmount? (y/N)\n"
            read yn
            if [ "$yn" != "y" ]; then
                exit 1
            fi
        fi

        umount -l $mntpoint

        # keep trying to kill processes accessing the device. don't exit until
        # we succeed
        while [ -n "$device" -a -e "$device" ]; do
            debug "attempting to kill all processes accessing $device\n"

            if [ "$interactive" ]; then
                fuser -kmi $device
            else
                fuser -km $device &> /dev/null
            fi

            if [ -z "`fuser -m $device`" ]; then
                success
            fi
        done

        printf "Lazy unmount succeeded, but I was unable to find the\n"
        printf "device the filesystem was mounted on. There may still be\n"
        printf "processes accessing the device.\n"

        exit 0
    else
        printf "%s failed... umount returned %d\n" "$SCRIPT" "$ret" >&2
        exit 1
    fi
fi