From a0fe51b32e5bf1a8c7b5e093683328f8b2f58d29 Mon Sep 17 00:00:00 2001
From: Kairui Song <kasong@redhat.com>
Date: Thu, 10 Jun 2021 13:06:22 +0800
Subject: [PATCH] kdumpctl: Add kdumpctl reset-crashkernel

Resolves: bz1974638
Upstream: Fedora
Conflict: None

commit 86130ec10fda37cc283f717eaacb56a4cbf76418
Author: Kairui Song <kasong@redhat.com>
Date:   Thu Jun 10 13:06:22 2021 +0800

    kdumpctl: Add kdumpctl reset-crashkernel

    In newer kernel, crashkernel.default will contain the default
    crashkernel value of a kernel build. So introduce a new sub command
    to help user reset kernel crashkernel size to the default value.

    Signed-off-by: Kairui Song <kasong@redhat.com>
    Acked-by: Baoquan He <bhe@redhat.com>

Signed-off-by: Kairui Song <kasong@redhat.com>
---
 kdumpctl   | 41 +++++++++++++++++++++++++++++++++++++++--
 kdumpctl.8 |  9 +++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/kdumpctl b/kdumpctl
index d24fe5f..fdd8d67 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -1308,6 +1308,40 @@ do_estimate() {
 	fi
 }
 
+reset_crashkernel() {
+	local kernel=$1 entry crashkernel_default
+	local grub_etc_default="/etc/default/grub"
+
+	[[ -z "$kernel" ]] && kernel=$(uname -r)
+	crashkernel_default=$(cat "/usr/lib/modules/$kernel/crashkernel.default" 2>/dev/null)
+
+	if [[ -z "$crashkernel_default" ]]; then
+		derror "$kernel doesn't have a crashkernel.default"
+		exit 1
+	fi
+
+	if is_atomic; then
+		if rpm-ostree kargs | grep -q "crashkernel="; then
+			rpm-ostree --replace="crashkernel=$crashkernel_default"
+		else
+			rpm-ostree --append="crashkernel=$crashkernel_default"
+		fi
+	else
+		entry=$(grubby --info ALL | grep "^kernel=.*$kernel")
+		entry=${entry#kernel=}
+		entry=${entry#\"}
+		entry=${entry%\"}
+
+		if [[ -f "$grub_etc_default" ]]; then
+			sed -i -e "s/^\(GRUB_CMDLINE_LINUX=.*\)crashkernel=[^\ \"]*\([\ \"].*\)$/\1$crashkernel_default\2/" "$grub_etc_default"
+		fi
+
+		[[ -f /etc/zipl.conf ]] && zipl_arg="--zipl"
+		grubby --args "$crashkernel_default" --update-kernel "$entry" $zipl_arg
+		[[ $zipl_arg ]] && zipl > /dev/null
+	fi
+    }
+
 if [ ! -f "$KDUMP_CONFIG_FILE" ]; then
 	derror "Error: No kdump config file found!"
 	exit 1
@@ -1366,8 +1400,11 @@ main ()
 	  estimate)
 		do_estimate
 		;;
+	  reset-crashkernel)
+		reset_crashkernel "$2"
+		;;
 	  *)
-		dinfo $"Usage: $0 {estimate|start|stop|status|restart|reload|rebuild|propagate|showmem}"
+		dinfo $"Usage: $0 {estimate|start|stop|status|restart|reload|rebuild|reset-crashkernel|propagate|showmem}"
 		exit 1
 	esac
 }
@@ -1377,6 +1414,6 @@ single_instance_lock
 
 # To avoid fd 9 leaking, we invoke a subshell, close fd 9 and call main.
 # So that fd isn't leaking when main is invoking a subshell.
-(exec 9<&-; main $1)
+(exec 9<&-; main "$@")
 
 exit $?
diff --git a/kdumpctl.8 b/kdumpctl.8
index a32a972..74be062 100644
--- a/kdumpctl.8
+++ b/kdumpctl.8
@@ -49,6 +49,15 @@ Prints the size of reserved memory for crash kernel in megabytes.
 Estimate a suitable crashkernel value for current machine. This is a
 best-effort estimate. It will print a recommanded crashkernel value
 based on current kdump setup, and list some details of memory usage.
+.TP
+.I reset-crashkernel [KERNEL]
+Reset crashkernel value to default value. kdumpctl will try to read
+from /usr/lib/modules/<KERNEL>/crashkernel.default and reset specified
+kernel's crashkernel cmdline value. If no kernel is
+specified, will reset current running kernel's crashkernel value.
+If /usr/lib/modules/<KERNEL>/crashkernel.default doesn't exist, will
+simply exit return 1.
+
 
 .SH "SEE ALSO"
 .BR kdump.conf (5),