From f41856349c99cf7ad6fd926b85fe6d025a045b5c Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Fri, 14 Jun 2024 11:17:30 +0200
Subject: [slx-dmsetup] Try to fix some snapshot brain damage

create_snapshot was always using hard-coded $writable_device, but
surrounding code at one callsite suggested it was expected to use
$scratch_device - this would at least explain why we could end up with
overlapping dm targets... -.-
---
 modules.d/slx-dmsetup/hooks/dmsetup-slx-device | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/modules.d/slx-dmsetup/hooks/dmsetup-slx-device b/modules.d/slx-dmsetup/hooks/dmsetup-slx-device
index 9fde7e3e..8e3b50ca 100755
--- a/modules.d/slx-dmsetup/hooks/dmsetup-slx-device
+++ b/modules.d/slx-dmsetup/hooks/dmsetup-slx-device
@@ -191,13 +191,13 @@ encrypt_device() {
 	fi
 	return 0
 }
-# create_snapshot "<name> <persist>"
+# create_snapshot "<name> <persist>" "cow_device"
 create_snapshot() {
 	modprobe dm-snapshot || echo "$0: dm-snapshot loading failed, maybe builtin?"
-	read -r name persist ignore <<< "$1"
+	read -r name persist _ <<< "$1"
 	if ! dmsetup_create_noudevsync "$name" \
-		"0 $read_only_device_sz snapshot $read_only_device $writable_device ${persist:-N} 8"; then
-		echo "$0: Failed to create snapshot on '$writable_device' for '$read_only_device'."
+		"0 $read_only_device_sz snapshot $read_only_device $2 ${persist:-N} 8"; then
+		echo "$0: Failed to create snapshot on '$2' for '$read_only_device'."
 		return 1
 	fi
 	return 0
@@ -245,7 +245,7 @@ ramdisk_fallback() {
 	fi
 
 	# create sparse file there
-	local file="$cow_tmpfs/thinpool.meta"
+	local file="$cow_tmpfs/tmpfs-snapshot"
 	if ! truncate -s "$(( read_only_device_sz * 512 ))" "$file" \
 			&& ! dd if=/dev/null of="$file" seek="$read_only_device_sz" bs=512; then
 		emergency_shell "Failed to allocate RAMdisk CoW file $file."
@@ -255,7 +255,7 @@ ramdisk_fallback() {
 	while [ -b "/dev/mapper/$cow_device_candidate" ]; do
 		cow_device_candidate="root.$RANDOM"
 	done
-	if [ -z "$writable_device" ] || ! create_snapshot "$cow_device_candidate N"; then
+	if [ -z "$writable_device" ] || ! create_snapshot "$cow_device_candidate N" "$writable_device"; then
 		emergency_shell "CRITICAL: failed to setup RAMdisk fallback."
 		exit 1
 	fi
@@ -824,11 +824,9 @@ fi
 ##	SNAPSHOT (OLD FUNCTIONALITY)
 ###
 if [ -n "$snapshot" ] && require_exact_scratch_size; then
-	read -r name crypt min max ignore <<< "$snapshot"
+	read -r name crypt min max _ <<< "$snapshot"
 	[ -n "$id44_crypted" ] && crypt=0
-	if ! create_snapshot "$name $persist"; then
-		echo "Failed to create regular snapshot for '$read_only_device' on '$scratch_device'."
-	else
+	if create_snapshot "$name N" "$scratch_device"; then
 		finish_setup "$name" "1" "$scratch_device_sz"
 	fi
 fi
-- 
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