#!/bin/sh

MOUNTDIR=/media/tmp_snapshot
loop=/dev/loop1


usage() {
        echo "Usage : $0 start|stop LV_PATH PART_NUMBER"
}

## @brief mount an lvm snapshot
# @param $1 lvpath (like /dev/vg0/lv0 )
# @param $2 partition number
snap_mount() {
        # Cleaning old killed mount or failed backup
        umount $MOUNTDIR/* 2>/dev/null
        losetup --detach $loop 2>/dev/null
        # Proc start
        name=$(basename $1)
        vgpath=$(dirname $1)
        snap="${name}-snap"
        lvcreate --snapshot --size 500M --name $vgpath/$snap $1
        losetup --partscan $loop $vgpath/$snap
        part="${loop}p$2"
        mkdir -v -p $MOUNTDIR/$name 2>/dev/null
        mount $part $MOUNTDIR/$name
        #echo $part mounted on $MOUNTDIR/$name
}

##@brief umount a previously created snapshot and removes it
snap_umount() {
        name=$(basename $1)
        vgpath=$(dirname $1)
        snap="${name}-snap"
        umount $MOUNTDIR/$name
        losetup --detach $loop
        lvremove -y $vgpath/$snap
}

case $1 in
        start)
                snap_mount $2 $3
                ;;
        stop)
                snap_umount $2 $3
                ;;
        *)
                usage
                exit 1
                ;;
esac