Introduce accessor function set_max_mapnr() to set global variable
max_mapnr.

Also unify condition compilation for max_mapnr with
CONFIG_NEED_MULTIPLE_NODES instead of CONFIG_DISCONTIGMEM.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
 include/linux/mm.h |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f9f9f3c..497ebaf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -25,8 +25,15 @@ struct file_ra_state;
 struct user_struct;
 struct writeback_control;
 
-#ifndef CONFIG_DISCONTIGMEM          /* Don't use mapnrs, do it properly */
+#ifndef CONFIG_NEED_MULTIPLE_NODES	/* Don't use mapnrs, do it properly */
 extern unsigned long max_mapnr;
+
+static inline void set_max_mapnr(unsigned long limit)
+{
+	max_mapnr = limit;
+}
+#else
+static inline void set_max_mapnr(unsigned long limit) { }
 #endif
 
 extern unsigned long totalram_pages;
-- 
1.7.9.5