From 071ea2a277e5b57bd0734a59a107e5876b152ed8 Mon Sep 17 00:00:00 2001
From: Xunlei Pang <xlpang@redhat.com>
Date: Sat, 29 Apr 2017 09:15:00 +0800
Subject: [PATCH] kdumpctl: bail out earlier in case of no reserved memory

Some cloud people complained that VM boot speed is slower than
Ubuntu and other distributions, after some debugging, we found
that one of the causes is kdump service starts too slow(7seconds
according to the test result on the test VM), actually there is
no "crashkernel=X" specified. Although kdump service is parallel,
it affects the speed more or less especially on VMs with few cpus,
which is unacceptable. It is even worse when kdump initramfs is
built out in case of no reserved memory at first boot.

Commit afa4a35d3 ("kdumpctrl: kdump feasibility should fail if no
crash memory") can actually solve this issue.

This patch is a supplement of above-mentioned commit, we bail out
start() even earlier in case of no reserved memory.

Also made some cosmatic changes for check_crash_mem_reserved().

1) Before this patch
$ time kdumpctl start
No memory reserved for crash kernel.
Starting kdump: [FAILED]

real    0m0.282s
user    0m0.184s
sys     0m0.146s

2) After this patch
$ time kdumpctl start
No memory reserved for crash kernel
Starting kdump: [FAILED]

real    0m0.010s
user    0m0.008s
sys     0m0.001s

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Acked-by: Pratyush Anand <panand@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
---
 kdumpctl | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/kdumpctl b/kdumpctl
index 6b5be09..129cb6a 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -1074,10 +1074,11 @@ is_secure_boot_enforced()
 
 check_crash_mem_reserved()
 {
-	MEM_RESERVED=$(cat /sys/kernel/kexec_crash_size)
-	if [ $MEM_RESERVED -eq 0 ]
-	then
-		echo "No memory reserved for crash kernel." >&2
+	local mem_reserved
+
+	mem_reserved=$(cat /sys/kernel/kexec_crash_size)
+	if [ $mem_reserved -eq 0 ]; then
+		echo "No memory reserved for crash kernel"
 		return 1
 	fi
 
@@ -1163,6 +1164,12 @@ check_default_config()
 
 start()
 {
+	check_dump_feasibility
+	if [ $? -ne 0 ]; then
+		echo "Starting kdump: [FAILED]"
+		return 1
+	fi
+
 	check_config
 	if [ $? -ne 0 ]; then
 		echo "Starting kdump: [FAILED]"
@@ -1172,13 +1179,8 @@ start()
 	if sestatus 2>/dev/null | grep -q "SELinux status.*enabled"; then
 		selinux_relabel
 	fi
-	save_raw
-	if [ $? -ne 0 ]; then
-		echo "Starting kdump: [FAILED]"
-		return 1
-	fi
 
-	check_dump_feasibility
+	save_raw
 	if [ $? -ne 0 ]; then
 		echo "Starting kdump: [FAILED]"
 		return 1