From 9ace072a507a2545e96e6267ba82d5a007ddf941 Mon Sep 17 00:00:00 2001
From: thomas <kreitler@molgen.mpg.de>
Date: Tue, 2 Nov 2021 18:23:09 +0100
Subject: [PATCH] crashkernel: check if crashmemory is available

If a kernel was started with crashmemory enabled, create
/node/startup-crashmemory/available.

This in turn will allow a conditional startup of the
startup-crashmemory.service.
---
 crashkernel/crashkernel.service         |  5 ++++-
 crashkernel/startup-crashmemory         | 21 +++++++++++++++++++++
 crashkernel/startup-crashmemory.service |  6 ++++++
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100755 crashkernel/startup-crashmemory
 create mode 100644 crashkernel/startup-crashmemory.service

diff --git a/crashkernel/crashkernel.service b/crashkernel/crashkernel.service
index fc7ec4b..2a2cf4c 100644
--- a/crashkernel/crashkernel.service
+++ b/crashkernel/crashkernel.service
@@ -1,5 +1,8 @@
 [Unit]
-Description=load crashkernel
+Description=load crashkernel if enabled
+Wants=startup-crashmemory.service
+After=startup-crashmemory.service
+ConditionPathExists=/node/startup-crashmemory/available
 ConditionPathExists=/boot/bzImage.crash
 
 [Service]
diff --git a/crashkernel/startup-crashmemory b/crashkernel/startup-crashmemory
new file mode 100755
index 0000000..8ba5f2c
--- /dev/null
+++ b/crashkernel/startup-crashmemory
@@ -0,0 +1,21 @@
+#! /bin/sh
+
+# Workaround for systemd versions missing certain ConditionXY= features.
+# This helper is called by startup-crashmemory.service and creates
+#   /node/startup-crashmemory/available
+# So other services can use
+#   Wants=startup-crashmemory.service
+#   After=startup-crashmemory.service
+#   ConditionPathExists=/node/startup-crashmemory/available
+# to start a unit only if the memory can be used
+#
+
+kexec_crash_size='0'
+if [ -e /sys/kernel/kexec_crash_size ]; then
+  kexec_crash_size=$(cat /sys/kernel/kexec_crash_size)
+fi
+mkdir -p /node/startup-crashmemory
+rm /node/startup-crashmemory/* 2>/dev/null
+if [ "$kexec_crash_size" != "0" ] ; then
+  touch /node/startup-crashmemory/available
+fi
diff --git a/crashkernel/startup-crashmemory.service b/crashkernel/startup-crashmemory.service
new file mode 100644
index 0000000..9f289c1
--- /dev/null
+++ b/crashkernel/startup-crashmemory.service
@@ -0,0 +1,6 @@
+[Unit]
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/sbin/startup-crashmemory