#!/bin/sh /etc/rc.common

START=15

ram_size()
{
	local line

	while read line; do case "$line" in MemTotal:*) set $line; echo "$2"; break ;; esac; done </proc/meminfo
}

zram_size()	# in megabytes
{
	local zram_size="$( uci -q get system.@system[0].zram_size_mb )"
	local ram_size="$( ram_size )"

	if [ -z "$zram_size" ]; then
		# e.g. 6mb for 16mb-routers or 61mb for 128mb-routers
		echo $(( ram_size / 2048 ))
	else
		echo "$zram_size"
	fi
}

zram_applicable()
{
	local zram_dev="$1"

	[ -e "$zram_dev" ] || {
		logger -s -t zram_applicable -p daemon.crit "[ERROR] device '$zram_dev' not found"
		return 1
	}

	which mkswap >/dev/null || {
		logger -s -t zram_applicable -p daemon.err "[ERROR] 'mkswap' not installed"
		return 1
	}

	which swapon >/dev/null || {
		logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapon' not installed"
		return 1
	}

	which swapoff >/dev/null || {
		logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapoff' not installed"
		return 1
	}
}

zram_dev()
{
	local idx="$1"
	echo "/dev/zram${idx:-0}"
}

zram_reset()
{
	local dev="$1"
	local message="$2"
	local proc_entry="/sys/block/$( basename "$dev" )/reset"

	logger -s -t zram_reset -p daemon.debug "$message via $proc_entry"
	echo "1" >"$proc_entry"
}

zram_getdev()
{
	#get unallocated zram dev
	local zdev=$( zram_dev )

	if [ "$(mount | grep $zdev)" ]; then
		local idx=`cat /sys/class/zram-control/hot_add`
		zdev="$( zram_dev $idx )"
	fi

	echo $zdev
}

zram_comp_algo()
{
	local dev="$1"
	local zram_comp_algo="$( uci -q get system.@system[0].zram_comp_algo )"

	if [ -z "$zram_comp_algo" ] || [ ! -e /sys/block/$( basename $dev )/comp_algorithm ]; then
		return 0
	fi

	if [ `grep -c "$zram_comp_algo" /sys/block/$( basename $dev )/comp_algorithm` -ne 0 ]; then
		logger -s -t zram_comp_algo -p daemon.debug "Set compression algorithm '$zram_comp_algo' for zram '$dev'"
		echo $zram_comp_algo > "/sys/block/$( basename $dev )/comp_algorithm"
	else
		logger -s -t zram_comp_algo -p daemon.debug "Compression algorithm '$zram_comp_algo' is not supported for '$dev'"
	fi
}

start()
{
	local zram_size="$( zram_size )"
	local zram_dev

	if [ $( grep -cs zram /proc/swaps ) -ne 0 ]; then
		logger -s -t zram_start -p daemon.notice "[OK] zram swap is already mounted"
		return 1
	fi

	zram_dev="$( zram_getdev )"
	zram_applicable "$zram_dev" || return 1

	logger -s -t zram_start -p daemon.debug "activating '$zram_dev' for swapping ($zram_size MegaBytes)"

	zram_reset "$zram_dev" "enforcing defaults"
	zram_comp_algo "$zram_dev"
	echo $(( $zram_size * 1024 * 1024 )) >"/sys/block/$( basename "$zram_dev" )/disksize"
	mkswap "$zram_dev"
	swapon "$zram_dev"
}

stop()
{
	local zram_dev

	for zram_dev in $( grep zram /proc/swaps |awk '{print $1}' ); do {
		logger -s -t zram_stop -p daemon.debug "deactivate swap $zram_dev"
		swapoff "$zram_dev" && zram_reset "$zram_dev" "claiming memory back"
		local dev_index="$( echo $zram_dev | grep -o "[0-9]*$" )"
		if [ $dev_index -ne 0 ]; then
			logger -s -t zram_stop -p daemon.debug "removing zram $zram_dev"
			echo $dev_index > /sys/class/zram-control/hot_remove
		fi
	} done
}