#!/sbin/openrc-run
# shellcheck shell=sh

# dm-cache
# A helper program to setup and manage device-mapper
# cache devices.
#
# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright 2023 Forza <forza@tnonline.net>

name="dm-cache ${dmname}"
description="Activates dm-cache devices"
extra_started_commands="suspend resume cleaner"
: "${cacheblock:=256}"
: "${cachemode:="1 writethrough"}"
: "${cachepolicy:="default"}"
: "${cachepolicyargs:=0}"
: "${readahead:="auto"}"

depend() {
	need dev modules
	use lvm
	before localmount
}

checkconfig() {
	if [ -z "${origindev}" ]; then
		eerror "origindev not set!"
		return 1
	fi
	if [ -z "${metadev}" ]; then
		eerror "metadev not set!"
		return 1
	fi
	if [ -z "${cachedev}" ]; then
		eerror "cachedev not set!"
		return 1
	fi
	if [ -z "${dmname}" ]; then
		eerror "dmname not set!"
		return 1
	fi
	# dm-cache requires the origindev size in sectors.
	: "${originsize:="$(/sbin/blockdev --getsz "${origindev}")"}"
}

start() {
	checkconfig || return 1
	ebegin "Creating dm-cache ${dmname}"

	if findmnt "${origindev}" > /dev/null; then
		eerror "Origin device is already mounted. Aborting."
		exit 1
	fi
	
	dmsetup create "${dmname}" --table "0 ${originsize} cache ${metadev} ${cachedev} ${origindev} ${cacheblock} ${cachemode} ${cachepolicy} ${cachepolicyargs}" --readahead "${readahead}"
	eend $?
}

stop() {
	if [ "$RC_RUNLEVEL" = "shutdown" ]; then
		if findmnt "/dev/mapper/${dmname}" > /dev/null; then
			ewarn "System is shutting down and \"${dmname}\" is still mounted!"
			ewarn "Attempting to unmount holders..."
			umount --all-targets "/dev/mapper/${dmname}" || eerror "Could not unmount!"
		fi
	else
		if findmnt "/dev/mapper/${dmname}" > /dev/null; then
			eerror "Cannot stop dm-cache. \"${dmname}\" is mounted!"
			exit 1
		fi
	fi
	ebegin "Stopping dm-cache ${dmname}"
	# Cannot flush or stop a suapended device.
	dmsetup resume "${dmname}"
	blockdev --flushbufs "/dev/mapper/${dmname}"
	einfo "Waiting for flush. This can take a while with large caches..."
	dmsetup remove "${dmname}"
	exit $?
}

cleaner() {
	# The Cleaner policy attempts to write out cached data
	# to the origin device at a higher rate. This is useful
	# if you want to remove or decomission the dm-cache.
	# Cleaner only makes sense for the 'writeback' mode.

	checkconfig || return 1
	ebegin "Enabling the Cleaner write cache policy."
	dmsetup suspend "${dmname}"
	dmsetup reload -r --table "0 ${originsize} cache ${metadev} ${cachedev} ${origindev} ${cacheblock} ${cachemode} cleaner 0" "${dmname}"
	errorlevel=$?
	if [ ! $errorlevel = 0 ]; then
		ewarn "Could not change to Cleaner policy"
	fi
	dmsetup resume "${dmname}"
	eend $?
}

suspend() {
	checkconfig || return 1
	if findmnt "/dev/mapper/${dmname}" > /dev/null; then
		ewarn "Warning, \"${dmname}\" is mounted!"
	fi
	ebegin "Suspending \"${dmname}\""
	dmsetup suspend "${dmname}"
	eend $?
}

resume() {
	checkconfig || return 1
	ebegin "Resuming \"${dmname}\""
	dmsetup resume "${dmname}"
	eend $?
}