Hi Andrew,

After merging the akpm-current tree, today's linux-next build (arm
multi_v7_defconfig) failed like this:

arm-linux-gnueabi-ld: kernel/sysctl.o: in function `.LANCHOR0':
sysctl.c:(.data+0x7b4): undefined reference to `fragment_stall_order_sysctl_handler'

Caused by commit

  a247ff3201c1 ("mm: stall movable allocations until kswapd progresses during serious external fragmentation event")

The fragment_stall_order_sysctl_handler() definition is protected by
CONFIG_NUMA, so I added this fix patch for today:

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Wed, 5 Dec 2018 16:05:51 +1100
Subject: [PATCH] mm: fix for "stall movable allocations until kswapd
 progresses during serious external fragmentation event"

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
 kernel/sysctl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2f445c82fe38..93352cfb3239 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1487,6 +1487,7 @@ static struct ctl_table vm_table[] = {
 		.extra1		= &one,
 		.extra2		= &one_thousand,
 	},
+#ifdef CONFIG_NUMA
 	{
 		.procname	= "fragment_stall_order",
 		.data		= &fragment_stall_order,
@@ -1496,6 +1497,7 @@ static struct ctl_table vm_table[] = {
 		.extra1		= &zero,
 		.extra2		= &max_order,
 	},
+#endif
 	{
 		.procname	= "percpu_pagelist_fraction",
 		.data		= &percpu_pagelist_fraction,
-- 
2.19.1

-- 
Cheers,
Stephen Rothwell