From f6ecfba9dc12daad0cd4dfba3cca8fa53a579a5f Mon Sep 17 00:00:00 2001
From: Jonathan Bauer
Date: Tue, 19 Nov 2019 11:40:45 +0100
Subject: try to grow qcow

---
 builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device b/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
index 64b12047..7dd1bab3 100755
--- a/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
+++ b/builder/modules.d/slx-dmsetup/scripts/dmsetup-slx-device
@@ -24,8 +24,8 @@ exec &> /run/openslx/dmsetup.log
 
 # read-only device to prepare for CoW
 [ -z "$1" ] && emergency_shell "Read-only device was not given!"
-declare -rg read_only_device="$1"
-declare -rg read_only_device_size="$(blockdev --getsz $1)"
+declare -g read_only_device="$1"
+declare -g read_only_device_size="$(blockdev --getsz $1)"
 
 # global array variables storing the configuration of the partitions
 declare -ag linear snapshot thin_snapshot thin_volume
@@ -146,6 +146,12 @@ ramdisk_fallback() {
 	local qcow_size_in_kb="$(( read_only_device_size / 2 ))"
 	local ram_size_in_kb="$(awk '/MemTotal/ {printf("%d\n", $2 )}' /proc/meminfo)"
 
+	# fill the qcow2 device with a zero device to make it larger than it is
+	dmsetup_create_noudevsync filler "0 $(( ram_size_in_kb / 2 )) zero"
+	echo "0 $(( read_only_device_size / 2 )) linear $read_only_device 0
+	0 $(( ram_size_in_kb / 2 )) linear /dev/mapper/filler 0" | dmsetup create bigger --noudevsync
+	dmsetup mknodes --noudevsync bigger
+
 	# Use the qcow size + half the RAM as tmpfs size.
 	local cow_size="$(( qcow_size_in_kb + ( ram_size_in_kb / 2 ) ))"
 	if ! mount -t tmpfs tmpfs -o size="${cow_size}k" "$cow_tmpfs"; then
@@ -157,6 +163,8 @@ ramdisk_fallback() {
 		emergency_shell "Failed to allocate CoW file $file."
 	fi
 	writable_device="$(losetup --show --find "$file")"
+	read_only_device=/dev/mapper/bigger
+	read_only_device_size="$cow_size"
 	cow_device_candidate="root"
 	while [ -b "/dev/mapper/$cow_device_candidate" ]; do
 		cow_device_candidate="root.$RANDOM"
-- 
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