#!/bin/bash

# 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