#!/bin/sh
# tested with busybox ash

fs='ext4:-q:-O:sparse_super2:-O:^has_journal:-O:dir_index:-O:^project:-O:^quota:-E:discard:-E:num_backup_sb=0:-b:4096'
#fs="$fs:-O:inline_data:-I:256"
fs="$fs:-O:^inline_data:-I:128"

# no remount
try=

# remount
try1='discard dioread_nolock noblock_validity lazytime nobarrier delalloc'

read kv </proc/sys/kernel/osrelease && [ "${kv%%.*}" -gt 3 ] || fs='ext4:-E:discard'

wait='true true true true true true false'

help="

mount.zram v0.15 (c) mahatma, under Anarchy license
Mount helper to mount zram (or ram/brd) devices via /etc/fstab over most simple way, stupid.
Usage:	mount -t zram ...
	mount.zram /dev/zram[<X>|'*'] <mountpoint> -o <options>
	mount.zram /dev/ram<X> <mountpoint> -o <options>
	mount.zram /dev/ram0 <mountpoint> -o disksize=<N>,<options>
Loading zram module with number of devices from FIRST mount device in fstab.
Loading brd module for /dev/ram0 ONLY.
Number is first unused (fstab or mounts) or <X>.
/dev/zram & /dev/zram* implies reset.
/dev/zram follow 'busy'-like mount-once behaviour.
Mount options:
	'fs=<fs[{:mkfs_options}]> (default fs=$fs, zram fs+=$fs_zram, ram fs+=$fs_ram),
	<zram_param>=<value> where <zram_param> is any file from /sys/block/zramX/
	zramctl=<options> - alternative to sysfs - use zramctl tool (spaces replaced to ':')
	disksize=<N> - for /dev/ram0 - compatible with zram, bound single brd/ram disk to N.
	other options pass directly to <fs> mount.
	First trying to mount with '-o dax,discard...', '-o discard...',
Examples of /etc/fstab:
	/dev/zram /tmp zram disksize=8g 0 0
	/dev/zram* /tmp zram comp_algorithm=lz4,disksize=8g,noatime 0 0
	/dev/zram0 /var/tmp/portage zram reset=1,comp_algorithm=zstd,disksize=12g,noatime,sync 0 0
	/dev/ram /var/cache/fscache zram disksize=1g,lazytime,dax,dioread_nolock,nobarrier,inode_readahead_blks=0,nodelalloc 0 0
    Over zramctl:
	/dev/zram3 /tmp zram zramctl=-alz4:-s8g 0 0
	/dev/zram3 /tmp zram zramctl=--algorithm=lz4:--size=8g 0 0
"

err(){
	{
	echo "
ERROR $0: $1" 
	caller
	} >&2
	exit ${2:-1}
}

warn(){
	echo "WARNING $0: ignored failed: $1" >&2
}

size2b(){
	local v="$1" x  l="${2:-1}"
	x="${v%?}"
	case "$v" in
	*k|*K)v=$((x*l));;
	*m|*M)v=$((x*1024*l));;
	*g|*G)v=$((x*1024*1024*l));;
	*t|*T)v=$((x*1024*1024*1024*l));;
	esac
	echo "$v"
}

disksize=
w=true

case "$1" in
/dev/zram|/dev/zram\*)
	[ "$1" = /dev/zram ] && grep -so "^/dev/zram[0-9]* $2 " /proc/mounts && err "- already mounted. Or use '/dev/zram*' to mount over."
	j=0
	# respect commented out fstab entries too
	while grep -sq "^[ 	#]*/dev/zram$j[ 	]" /etc/fstab /proc/mounts || (f="/sys/block/zram$j/reset" && [ -e $f ] && ! echo 1 >$f) ; do
		j=$((j+1))
	done
	shift
	set -- /dev/zram$j "${@}"
;;
/dev/ram0)
	for j in ${4//,/ }; do
		v="${j#disksize=}"
		[ "$v" = "$j" ] || disksize="$(size2b "$v")"
	done
	[ -n "$disksize" ] && modprobe brd rd_nr=1 rd_size="$disksize" max_part=0 && w=true
;;
esac >&2

n="${1##*/}"
i="/sys/block/$n"
c="$i"
#w=false
case "$1" in
/dev/*/*)err "$*$help";;
/dev/zram*)
	[ -e "$1" ] || {
		nn=${1#/dev/zram}
		nn=$((nn+0))
		ha=/sys/class/zram-control/hot_add
		[ "$1" = "/dev/zram$nn" -a "$nn" -ge 0 ] &&
		if [ -e $ha ]; then
			j1=
			while read j <$ha && [ "$j" -lt "$nn" ]; do
				[ "$j" = "$j1" ] && break
				j1="$j"
			done
			#w=true
		else
			modprobe zram num_devices=$((nn+1)) && w=true
		fi
	}
	c="$i/comp_algorithm"
	fs="$fs$fs_zram"
;;
/dev/ram*)
	try="$try dax"
	fs="$fs$fs_ram"
	c="$i/size"
;;
*)err "$*$help";;
esac
$w && for w in $w $wait; do
	[ -e "$c" ] && break
	sleep 0.1
done
[ -e "$c" ] || err "no $c"
echo 0 >"$i/queue/rotational"
[ "$3" = '-o' -o "$3" = '' ] || err "invalid option '$3'"
o=
w=true
sw=false
for i in ${4//,/ }; do
	case "$i" in
	sw)eval "$i=true";;
	*=*)
		v="${i#*=}"
		x="${i%%=*}"
		case "$x" in
		disksize)[ -n "$disksize" ] && continue;; # /dev/ram0
		zramctl) # unify mkfs here?
			c="$x ${v//:/ } $1"
			$c || err "$c"
			continue
		;;
		mode|uid|gid)eval "$x=\"\$v\"";;
		fs)eval "$x=\"\$v\"";continue;;
		esac
		f="/sys/block/$n/$x"
		[ -e "$f" ] && {
			# after modprobe reset not ready
			for w in $w $wait; do
				echo "$v" >"$f" && continue 2
				$w || break
				sleep 0.1
			done
			v1="$(cat "$f")" && [ -n "$v1" ] && ( [ "$v1" = "$v" ] || [ "$v1" = "$(size2b "$v" 1024)" ] || [ -z "${v1##*\[$v\]*}" ] ) && continue
			e="echo \"$v\" >$f # $v1 - $e"
			case "$x" in
			*algorithm*)echo "WARNING: $e" >&2;;
			*)err "$e";;
			esac
		}
	;;
	esac
	o="$o,$i"
done
[ -b "$1" ] || err " -b $1$help"
o="${o#,}"

$sw && {
	mkswap "$1" || warn "mkswap $1"
	swapon -o "discard,$o" "$1" || swapon -o "$o" "$1" || err "swapon -o $o $1"
	exit 0
} >/dev/null

fs="${fs//:/ }"
mkfs="mkfs.$fs $1"
fs="${fs%% *}"

re=",$4,"
[ -z "${re##*,remount,*}" ] || yes '' | $mkfs || warn "$mkfs"

# move original mountpoint permissions to mount if not fs-assisted
[ -z "$mode" ] && m=`stat "$2" -c '%a'`
[ -z "$uid$gid" ] && ug=`stat "$2" -c '%u:%g'` || ug=

t1="${try1// /,}"
for i in $try ''; do
    for i in "$t1,$i" "$i" ; do
	[ -n "$i" -a -n "$o" ] && i="$i,$o" || i="$i$o"
	mount -t "$fs"${i:+ -o }"$i" "$1" "$2" && {
		case "$i,1" in
		$t1,*);;
		*)for i1 in $try1; do
			mount -t "$fs" -o "remount,$i1${i:+,$i}" "$1" "$2"
		done;;
		esac
		[ -n "$m" ] && chmod -- "$m" "$2"
		[ -n "$ug" ] && chown -- "$ug" "$2"
		exit 0
	}
	r=$?
    done
done
err "mount -t $fs ${o+-o $o} $1 $2" $r