#!/bin/bash

### BEGIN INIT INFO
# Provides: zram
# Required-Start:
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Increased Performance In Linux With zRam (Virtual Swap Compressed in RAM)
# Description: Adapted from systemd scripts at https://github.com/mystilleef/FedoraZram
### END INIT INFO

DEFAULTS="/etc/default/zram"

# Include defaults if available
[ -r "$DEFAULTS" ] && . "$DEFAULTS"

# Get lsb functions
. /lib/lsb/init-functions

start() {
    # Add support of defaults file parameter - ZRAM_NDEVS
    if [ -z "$ZRAM_NDEVS" ] || [ "$ZRAM_NDEVS" -le "0" ]; then
	# get the number of CPUs
	num_cpus=$(grep -c processor /proc/cpuinfo)
    else
	# or just use user specified
	num_cpus=$ZRAM_NDEVS
    fi

    # if something goes wrong, assume we have 1
    [ "$num_cpus" != 0 ] || num_cpus=1

    decr_num_cpus=$((num_cpus - 1))

    # find module and it's param name
    error_file=$(mktemp ${RC_NAME}XXXXXX) # storage for error message
    param_name=$(/usr/bin/env modinfo --parameters zram 2>$error_file | head -1 | cut -d: -f1)
    error_message=$(<$error_file)
    rm -f $error_file
    mod_found=$?


    # load dependency modules
    if [ "$mod_found" == 0 ]; then
	log_begin_msg "Loading zRAM kernel module"
	modprobe zram "$param_name=$num_cpus"
	log_end_msg $?
    else
	log_failure_msg "Failed to load zRAM kernel module: ${error_message}"
	# shit happens, yep.
	exit $mod_found
    fi

    # get the amount of memory in the machine
    mem_total_kb=$(fgrep MemTotal /proc/meminfo | grep -E --only-matching '[[:digit:]]+')
    mem_total=$((mem_total_kb * 1024))

    # Add support of defaults file parameter - ZRAM_USE_PERCENT
    if [ -z "$ZRAM_USE_PERCENT" ] || [ "$ZRAM_USE_PERCENT" -le "0" ] || [ "$ZRAM_USE_PERCENT" -gt "100" ]; then
	# use 100% of ram for zRAM storage (suitable for low-ram laptops)
	use_percent=100
    else
	# or just use user specified
	use_percent=$ZRAM_USE_PERCENT
    fi

    zsize=$((use_percent * mem_total / num_cpus / 100))

    # initialize the devices
    for i in $(seq 0 $decr_num_cpus); do
	echo $zsize > /sys/block/zram$i/disksize
    done

    # get page size
    page_size=$(/usr/bin/env getconf PAGESIZE || /usr/bin/env getconf PAGE_SIZE)

    # Creating swap filesystems
    for i in $(seq 0 $decr_num_cpus); do
	msg=">  Making swap on /dev/zram$i"
	mkswap -p $page_size /dev/zram$i 2>&1 >/dev/null
	[ "$?" -eq "0" ] && log_success_msg $msg || log_failure_msg $msg
    done

    # Switch the swaps on
    for i in $(seq 0 $decr_num_cpus); do
	msg=">>  Activating swap on /dev/zram$i"
	swapon -p 100 /dev/zram$i
	[ "$?" -eq "0" ] && log_success_msg $msg || log_failure_msg $msg
    done

    # TODO FIXME need strict error reporting
    # log_end_msg 0
}

stop() {
    # Switching off swap ASAP
    for zswap in $(fgrep /dev/zram /proc/swaps | cut -d' ' -f1); do
	    swapoff $zswap
    done

    # Custom kernels can contain zram compiled-in
    [ -z "$(fgrep zram /proc/modules)" ] || rmmod zram
}

case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        sleep 3
        start
        ;;
    *)
        echo "Usage: $0 {start|stop|restart}"
        RETVAL=1
esac