From 987edab69aa1d0d9aabf27bf6f388740c4e1eed3 Mon Sep 17 00:00:00 2001
From: Lichen Liu <lichliu@redhat.com>
Date: Jun 17 2022 03:20:15 +0000
Subject: kdump-lib: use non-debug kernels first


Resolves: bz2076425
Upstream: Fedora
Conflict: None

commit c5bdd2d8f195103d6651f7fa3b429f4edf204956
Author: Lichen Liu <lichliu@redhat.com>
Date:   Mon Jun 13 12:08:08 2022 +0800

    kdump-lib: use non-debug kernels first

    Kdump uses currently running kernel as default, but when currently
    running kernel is a debug kernel, it will consume more memory,
    which may cause out-of-memory and fail to collect vmcore.

    Now we will try to use non-debug kernels first if possible.

    Also extract the logic of determine KDUMP_KERNEL from
    prepare_kdump_bootinfo into a function. This function will return
    KDUMP_KERNEL given a kernel version.

    Signed-off-by: Lichen Liu <lichliu@redhat.com>
    Acked-by: Coiby Xu <coxu@redhat.com>

Signed-off-by: Lichen Liu <lichliu@redhat.com>

---

diff --git a/kdump-lib.sh b/kdump-lib.sh
index 099cbfb..2b58ddd 100755
--- a/kdump-lib.sh
+++ b/kdump-lib.sh
@@ -630,46 +630,77 @@ prepare_kexec_args()
 	echo "$kexec_args"
 }
 
-#
-# Detect initrd and kernel location, results are stored in global enviromental variables:
-# KDUMP_BOOTDIR, KDUMP_KERNELVER, KDUMP_KERNEL, DEFAULT_INITRD, and KDUMP_INITRD
-#
-# Expectes KDUMP_BOOTDIR, KDUMP_IMG, KDUMP_IMG_EXT, KDUMP_KERNELVER to be loaded from config already
-# and will prefer already set values so user can specify custom kernel/initramfs location
-#
-prepare_kdump_bootinfo()
+# prepare_kdump_kernel <kdump_kernelver>
+# This function return kdump_kernel given a kernel version.
+prepare_kdump_kernel()
 {
-	local boot_img boot_imglist boot_dirlist boot_initrdlist
-	local machine_id dir img default_initrd_base var_target_initrd_dir
-
-	if [[ -z $KDUMP_KERNELVER ]]; then
-		KDUMP_KERNELVER="$(uname -r)"
-	fi
-
+	local kdump_kernelver=$1
+	local dir img boot_dirlist boot_imglist kdump_kernel machine_id
 	read -r machine_id < /etc/machine-id
+
 	boot_dirlist=${KDUMP_BOOTDIR:-"/boot /boot/efi /efi /"}
-	boot_imglist="$KDUMP_IMG-$KDUMP_KERNELVER$KDUMP_IMG_EXT $machine_id/$KDUMP_KERNELVER/$KDUMP_IMG"
+	boot_imglist="$KDUMP_IMG-$kdump_kernelver$KDUMP_IMG_EXT $machine_id/$kdump_kernelver/$KDUMP_IMG"
 
 	# Use BOOT_IMAGE as reference if possible, strip the GRUB root device prefix in (hd0,gpt1) format
 	boot_img="$(sed "s/^BOOT_IMAGE=\((\S*)\)\?\(\S*\) .*/\2/" /proc/cmdline)"
-	if [[ -n $boot_img ]]; then
+	if [[ "$boot_img" == *"$kdump_kernelver" ]]; then
 		boot_imglist="$boot_img $boot_imglist"
 	fi
 
 	for dir in $boot_dirlist; do
 		for img in $boot_imglist; do
 			if [[ -f "$dir/$img" ]]; then
-				KDUMP_KERNEL=$(echo "$dir/$img" | tr -s '/')
+				kdump_kernel=$(echo "$dir/$img" | tr -s '/')
 				break 2
 			fi
 		done
 	done
+	echo "$kdump_kernel"
+}
+
+#
+# Detect initrd and kernel location, results are stored in global environmental variables:
+# KDUMP_BOOTDIR, KDUMP_KERNELVER, KDUMP_KERNEL, DEFAULT_INITRD, and KDUMP_INITRD
+#
+# Expectes KDUMP_BOOTDIR, KDUMP_IMG, KDUMP_IMG_EXT, KDUMP_KERNELVER to be loaded from config already
+# and will prefer already set values so user can specify custom kernel/initramfs location
+#
+prepare_kdump_bootinfo()
+{
+	local boot_initrdlist nondebug_kernelver debug_kernelver
+	local default_initrd_base var_target_initrd_dir
+
+	if [[ -z $KDUMP_KERNELVER ]]; then
+		KDUMP_KERNELVER=$(uname -r)
+		nondebug_kernelver=$(sed -n -e 's/\(.*\)+debug$/\1/p' <<< "$KDUMP_KERNELVER")
+	fi
+
+	# Use nondebug kernel if possible, because debug kernel will consume more memory and may oom.
+	if [[ -n $nondebug_kernelver ]]; then
+		dinfo "Trying to use $nondebug_kernelver."
+		debug_kernelver=$KDUMP_KERNELVER
+		KDUMP_KERNELVER=$nondebug_kernelver
+	fi
+
+	KDUMP_KERNEL=$(prepare_kdump_kernel "$KDUMP_KERNELVER")
+
+	if ! [[ -e $KDUMP_KERNEL ]]; then
+		if [[ -n $debug_kernelver ]]; then
+			dinfo "Fallback to using debug kernel"
+			KDUMP_KERNELVER=$debug_kernelver
+			KDUMP_KERNEL=$(prepare_kdump_kernel "$KDUMP_KERNELVER")
+		fi
+	fi
 
 	if ! [[ -e $KDUMP_KERNEL ]]; then
 		derror "Failed to detect kdump kernel location"
 		return 1
 	fi
 
+	if [[ "$KDUMP_KERNEL" == *"+debug" ]]; then
+		dwarn "Using debug kernel, you may need to set a larger crashkernel than the default value."
+	fi
+
 	# Set KDUMP_BOOTDIR to where kernel image is stored
 	KDUMP_BOOTDIR=$(dirname "$KDUMP_KERNEL")