#!/bin/sh
# Configure zram
# Didier Spaier 2020
# Dedicated to the public domain as stated in https://unlicense.org/
[ $(id -u) -ne 0 ] && echo "This script should be run as root." && exit
if  [ -f /etc/swapinzram.conf ]; then
	. /etc/swapinzram.conf
fi
usage() {
	echo "usage: $0 start|stop|status|restart"
}
start() {
	if lsblk -lno name,mountpoint|grep ^zram|grep -q SWAP; then
		echo "A zram block device for swap is already active."
		exit
	fi
	modprobe zram
	cat /proc/sys/vm/swappiness > /var/lib/swappiness
	KRAM=$(sed -n 1p /proc/meminfo|sed "s/[ ]\{1,\}/ /"|cut -d" " -f2)
	COMPRESSION_ALGORITHM=${COMPRESSION_ALGORITHM:-zstd}
	DISKID=$(cat /sys/class/zram-control/hot_add)
	echo $DISKID > /var/lib/zramswapdiskid
	echo $COMPRESSION_ALGORITHM >  /sys/block/zram$DISKID/comp_algorithm
	PERCENTAGE=${PERCENTAGE:-200}
	echo $((KRAM * PERCENTAGE / 100))K >/sys/block/zram$DISKID/disksize
	PRIORITY=${PRIORITY:-32567}
	mkswap /dev/zram$DISKID
	swapon -p $PRIORITY /dev/zram$DISKID
	SWAPPINESS=${SWAPPINESS:-80}
	echo $SWAPPINESS > /proc/sys/vm/swappiness
}
stop() {
	if ! lsblk -lno name,mountpoint|grep ^zram|grep -q SWAP; then
		echo "No active zram swap device."
		return
	else
		DISKID=$(cat /var/lib/zramswapdiskid)
		swapoff /dev/zram$DISKID
		echo 1 > /sys/block/zram$DISKID/reset
		echo $DISKID > /sys/class/zram-control/hot_remove
		rm -f /var/lib/zramswapdiskid
		cat /var/lib/swappiness > /proc/sys/vm/swappiness
	fi
}
status() {
	if ! lsblk -lno name,mountpoint|grep ^zram|grep -q SWAP; then
		echo "No active zram swap block device."
	else
		# To do: rewrite the output using directly the /sys interface to not
		# depend on zramctl at all.
		# lsblk -I 252 -o path,size,mountpoint
		/sbin/zramctl
	fi
}
restart() {
	stop && start
}
case $1 in
	start|stop|restart|status|restart) $1 ;;
	*) usage
esac