Address CPU/memory hot plugging for kdump LUKS support

We can reuse LUKS volume keys when there is CPU/memory hot plugging by
writing 1 to /sys/kernel/config/crash_dm_crypt_keys/resue to reuse keys
already saved to kdump reserved memory.

Signed-off-by: Coiby Xu <[email protected]>

Author: coiby

kdump-udev-throttler

@@ -15,6 +15,17 @@
 
 throttle_lock="/var/lock/kdump-udev-throttle"
 
+LUKS_CONFIGFS_REUSE=/sys/kernel/config/crash_dm_crypt_keys/reuse
+reuse_luks_keys()
+{
+	[[ -f $LUKS_CONFIGFS_REUSE ]] || echo 1 > $LUKS_CONFIGFS_REUSE
+}
+
+unuse_luks_keys()
+{
+
+	[[ -f $LUKS_CONFIGFS_REUSE ]] || echo 0 > $LUKS_CONFIGFS_REUSE
+}
 exec 9> $throttle_lock
 if [ $? -ne 0 ]; then
 	echo "Failed to create the lock file! Fallback to non-throttled kdump service restart"
@@ -37,6 +48,8 @@ sleep 1 && udevadm settle --timeout 3
 # holding two locks at the same time and we might miss some events
 exec 9>&-
 
+reuse_luks_keys
 /bin/kdumpctl reload
+unuse_luks_keys
 
 exit 0

kdumpctl

@@ -1105,6 +1105,9 @@ prepare_luks()
 		return 1
 	fi
 
+	# For the case of CPU/memory hotplugging, we can reuse loaded keys
+	[[ $(cat $LUKS_CONFIGFS/reuse) == 1 ]] && return 0
+
 	for _luks_dev in "${_luks_devs[@]}"; do
 		_devuuid=$(maj_min_to_uuid "$_luks_dev")
 		_key_dir=$LUKS_CONFIGFS/$_devuuid