zram: properly implement systemd service

The systemd service points ot a script which is not installed by
zram or any of its dependencies. It seems that the service got
migrated without the necessary script.

The sysvinit script seems rather dated and initializes multiple
zram instances to support multiprocessor systems. This is no
longer necessary with modern implementations as newer kernel
version support multiple streams by default.

Create a modern implementation based on Fedoras zram package.
Make use of systemd swap unit files instead of enabling swap
directly.

This removes the need for util-linux-swaponoff (since swap is
now handled by systemd, which presumably depends on swaponoff).
However, it adds the dependency to util-linux for zramctl.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-extended/zram/zram/dev-zram0.swap

@@ -0,0 +1,10 @@
+[Unit]
+Description=Enable compressed swap in memory using zram
+Requires=zram-swap.service
+After=zram-swap.service
+
+[Swap]
+What=/dev/zram0
+
+[Install]
+WantedBy=swap.target

meta-oe/recipes-extended/zram/zram/zram-swap-deinit

@@ -0,0 +1,19 @@
+#!/bin/sh
+set -e
+
+device=$1
+if [ "$device" = "" ]; then
+    echo "Usage: zram-swap-deinit <device>"
+    exit 1
+fi
+
+sysblockdev=/sys/block/$(basename $device)
+if [ ! -d $sysblockdev ]; then
+    echo "Block device not found in sysfs"
+    exit 1
+fi
+
+# zramctl -r is not suitable as it also removes the actual device. Recreating
+# it is non-trivial, especially if not /dev/zram0 is used...
+echo 1 > ${sysblockdev}/reset
+

meta-oe/recipes-extended/zram/zram/zram-swap-init

@@ -0,0 +1,26 @@
+#!/bin/sh
+set -e
+
+device=$1
+if [ "$device" = "" ]; then
+    echo "Usage: zram-swap-init <device>"
+    exit 1
+fi
+
+# Allocate zram to be size of actual system memory
+# Note: zram is only allocated when used. When swapped pages compress with a
+# a 2:1 ratio zram will require 50% of system memory (while allowing to use
+# 150% memory).
+ZRAM_SIZE_PERCENT=100
+ZRAM_ALGORITHM=lz4
+
+[ -f /etc/default/zram ] && ./etc/default/zram || true
+
+memtotal=$(grep MemTotal /proc/meminfo | awk ' { print $2 } ')
+memzram=$(($memtotal*${ZRAM_SIZE_PERCENT}/100))
+
+# Try loading zram module
+modprobe -q zram || true
+
+zramctl -a ${ZRAM_ALGORITHM} -s ${memzram}KB $device
+mkswap -L "zram-swap" $device

meta-oe/recipes-extended/zram/zram/zram-swap.service

@@ -0,0 +1,10 @@
+[Unit]
+Description=Create compressed swap in memory using zram
+DefaultDependencies=no
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+TimeoutStartSec=30sec
+ExecStart=@LIBEXECDIR@/zram-swap-init /dev/zram0
+ExecStop=@LIBEXECDIR@/zram-swap-deinit /dev/zram0

meta-oe/recipes-extended/zram/zram/zram.service

@@ -1,12 +0,0 @@
-[Unit]
-Description=Enable zram compressed in-memory swap.
-After=multi-user.target
-
-[Service]
-RemainAfterExit=yes
-ExecStart=/usr/bin/zram-load.sh --load
-ExecStop=/usr/bin/zram-load.sh --unload
-Type=oneshot
-
-[Install]
-WantedBy=multi-user.target

meta-oe/recipes-extended/zram/zram/zramstop

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+for i in $(grep '^/dev/zram' /proc/swaps | awk '{ print $1 }'); do
+	swapoff "$i" && zramctl --reset "$i"
+done

meta-oe/recipes-extended/zram/zram_0.1.bb

@@ -1,33 +0,0 @@
-SUMMARY = "Linux zram compressed in-memory swap"
-LICENSE = "MIT"
-LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
-
-inherit update-rc.d systemd
-
-RDEPENDS_${PN} = "util-linux-swaponoff kmod"
-RRECOMMENDS_${PN} = "kernel-module-zram"
-
-PR = "r3"
-
-SRC_URI = " \
-           file://init \
-           file://zram.service \
-"
-
-do_install () {
-    # Sysvinit
-    install -d ${D}${sysconfdir}/init.d
-    install -m 0755 ${WORKDIR}/init ${D}${sysconfdir}/init.d/zram
-
-    install -d ${D}${systemd_unitdir}/system
-    install -m 0644 ${WORKDIR}/zram.service ${D}${systemd_unitdir}/system
-}
-
-FILES_${PN} = "${sysconfdir}"
-INITSCRIPT_NAME = "zram"
-INITSCRIPT_PARAMS = "start 05 2 3 4 5 . stop 22 0 1 6 ."
-
-RPROVIDES_${PN} += "${PN}-systemd"
-RREPLACES_${PN} += "${PN}-systemd"
-RCONFLICTS_${PN} += "${PN}-systemd"
-SYSTEMD_SERVICE_${PN} = "zram.service"

meta-oe/recipes-extended/zram/zram_0.2.bb

@@ -0,0 +1,50 @@
+SUMMARY = "Linux zram compressed in-memory swap"
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
+
+inherit update-rc.d systemd
+
+RDEPENDS_${PN} = "kmod \
+    ${@bb.utils.contains('DISTRO_FEATURES','systemd','util-linux','util-linux-swaponoff',d)}"
+RRECOMMENDS_${PN} = "kernel-module-zram"
+
+PR = "r3"
+
+SRC_URI = " \
+           file://init \
+           file://zram-swap-init \
+           file://zram-swap-deinit \
+           file://zram-swap.service \
+           file://dev-zram0.swap \
+"
+
+do_install () {
+    # Install systemd related configuration file
+    if ${@bb.utils.contains('DISTRO_FEATURES', 'sysvinit', 'true', 'false', d)}; then
+        install -d ${D}${sysconfdir}/init.d
+        install -m 0755 ${WORKDIR}/init ${D}${sysconfdir}/init.d/zram
+    fi
+
+    if ${@bb.utils.contains('DISTRO_FEATURES', 'systemd', 'true', 'false', d)}; then
+        install -d ${D}${libexecdir}
+        install -m 0755 ${WORKDIR}/zram-swap-init ${D}${libexecdir}
+        install -m 0755 ${WORKDIR}/zram-swap-deinit ${D}${libexecdir}
+        install -d ${D}${systemd_unitdir}/system
+        install -m 0644 ${WORKDIR}/zram-swap.service ${D}${systemd_unitdir}/system/zram-swap.service
+        sed -i -e "s,@LIBEXECDIR@,${libexecdir},g" ${D}${systemd_unitdir}/system/zram-swap.service
+        install -m 0644 ${WORKDIR}/dev-zram0.swap ${D}${systemd_unitdir}/system/dev-zram0.swap
+    fi
+}
+
+FILES_${PN} = " \
+    ${sysconfdir} \
+    ${systemd_unitdir} \
+    ${libexecdir} \
+"
+INITSCRIPT_NAME = "zram"
+INITSCRIPT_PARAMS = "start 05 2 3 4 5 . stop 22 0 1 6 ."
+
+RPROVIDES_${PN} += "${PN}-systemd"
+RREPLACES_${PN} += "${PN}-systemd"
+RCONFLICTS_${PN} += "${PN}-systemd"
+SYSTEMD_SERVICE_${PN} = "dev-zram0.swap"