From 2c9e3cf746d577d3d66245cf1753887c3ccb8244 Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Fri, 2 Oct 2020 11:07:39 +0200
Subject: [slx-dmsetup] part-table: Allow different units for min and max

It can useful to specify a minumum size in absolute terms, but have the
maximum value be a percentage of the writable device.
---
 modules.d/slx-dmsetup/scripts/dmsetup-slx-device | 83 +++++++++++++++---------
 1 file changed, 51 insertions(+), 32 deletions(-)

diff --git a/modules.d/slx-dmsetup/scripts/dmsetup-slx-device b/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
index ff25e167..dffc203c 100755
--- a/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
+++ b/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
@@ -32,6 +32,31 @@ declare -g read_only_device_sz="$( blockdev --getsz "$1" )"
 
 declare -rg ntfs_list="/run/openslx/.thin-ntfs-candidates"
 
+# handle_unit <value> <unit>
+# Supply percentage, or size in [kmgt]bytes,
+# returns appropriate value in number of 512b sectors
+handle_unit() {
+	# default to bytes
+	local -i potency=0
+	local -i val="$1"
+	case "$2" in
+		[%]) # These are relative to the writable CoW device
+			# Allow > 100% for over-provisioning
+			val="$(( writable_device_sz * val / 100 ))"
+			;;
+		[Kk])	potency=1 ;;&
+		[Mm])	potency=2 ;;&
+		[Gg])	potency=3 ;;&
+		[Tt])	potency=4 ;;&
+		*)
+			# => 1024 ** potency for G, M, K, etc results in bytes
+			# => bytes / 512 = sectors
+			val=$(( val * ( 1024 ** potency) / 512 ))
+			;;
+	esac
+	echo "$val"
+}
+
 # global array variables storing the configuration of the partitions
 declare -ag linear snapshot thin_snapshot thin_volume
 parse_config() {
@@ -49,42 +74,36 @@ parse_config() {
 			echo "$0: Ignoring nameless entry: $line"
 			continue
 		fi
-		unset unit min max
-		# ranges can be like: 40G, 40-80G, 10-20%
-		if ! [[ $range =~ ^([0-9]+-)*([0-9])+[GgMmKkBb%]$ ]]; then
+		unset min_unit max_unit min max
+		# ranges can be like: 40G, 40-80G, 10G-20%
+		if ! [[ "$range" =~ ^([0-9]+)([GgMmKkBb%]?)(-([0-9]+)([GgMmKkBb%]?))?$ ]]; then
 			echo "$0: Ignoring invalid range: $line"
 			continue
 		fi
-		# process ranges: convert percentages (of read_only_device!)
-		# to actual sizes (in sectors!) before saving them
-		local unit=${range: -1}
-		local min="$(cut -d'-' -f1 <<< "${range%?}" )"
-		local max="$(cut -d'-' -f2 <<< "${range%?}" )"
-		if [ "$min" -gt "$max" ]; then
-			echo "$0: Ignoring invalid range: $line"
-			continue
+		local min="${BASH_REMATCH[1]}"
+		local max="${BASH_REMATCH[4]:-${BASH_REMATCH[1]}}"
+		local min_unit="${BASH_REMATCH[2]:-${BASH_REMATCH[5]}}"
+		local max_unit="${BASH_REMATCH[5]:-${BASH_REMATCH[2]}}"
+		if [ -z "$min_unit" ]; then
+			echo "$0: WARNING: No unit given in range, assuming BYTES: $line"
+		fi
+		min="$( handle_unit "$min" "$min_unit" )"
+		max="$( handle_unit "$max" "$max_unit" )"
+		if (( min > max )); then
+			# So, we might end up with something like 30G-100%, but the writable device
+			# is only 20GB. In that case we most likely want to contine, and not consider
+			# this an error. So let's try to come up with some logic on what is an error
+			# and what isn't. Probably anything involving a mix of percentage and
+			# non-percentage should not be an error.
+			if [[ "$min_unit" = "%" && "$max_unit" != "%" ]] \
+					|| [[ "$min_unit" != "%" && "$max_unit" = "%" ]]; then
+				# Let's hope for the best
+				max="$min"
+			else
+				echo "$0: Ignoring invalid range (min > max): $line"
+				continue
+			fi
 		fi
-		# default for bytes
-		local -i potency=0
-		case "$unit" in
-			[%])
-				if [ "$max" -gt 100 ]; then
-					echo "Ignoring invalid percentages: $min/$max"
-					continue
-				fi
-				min=$(( writable_device_sz * min / 100 ))
-				max=$(( writable_device_sz * max / 100 ))
-				;;
-			[Kk])	potency=1 ;;&
-			[Mm])	potency=2 ;;&
-			[Gg])	potency=3 ;;&
-			*)
-				# => 1024 ** potency for G, M, K, etc results in bytes
-				# => bytes / 512 = sectors
-				min=$(( min * ( 1024 ** potency) / 512 ))
-				max=$(( max * ( 1024 ** potency) / 512 ))
-				;;
-		esac
 		if ! [[ "$crypt"  =~ ^[01]$ ]]; then
 			echo "$0: Disabling encryption due to invalid crypt argument: $line"
 			crypt=0
-- 
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