mm: only define hashdist variable when needed

For !CONFIG_NUMA, hashdist will always be 0, since it's setter is
otherwise compiled out.  So we can save 4 bytes of data and some .text
(although mostly in __init functions) by only defining it for
CONFIG_NUMA.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index 0995c2d..f589222 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -357,12 +357,12 @@
 /* Only NUMA needs hash distribution. 64bit NUMA architectures have
  * sufficient vmalloc space.
  */
-#if defined(CONFIG_NUMA) && defined(CONFIG_64BIT)
-#define HASHDIST_DEFAULT 1
-#else
-#define HASHDIST_DEFAULT 0
-#endif
+#ifdef CONFIG_NUMA
+#define HASHDIST_DEFAULT IS_ENABLED(CONFIG_64BIT)
 extern int hashdist;		/* Distribute hashes across NUMA nodes? */
+#else
+#define hashdist (0)
+#endif
 
 
 #endif /* _LINUX_BOOTMEM_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ebffa0e..159dbbc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6013,9 +6013,9 @@
 	return ret;
 }
 
+#ifdef CONFIG_NUMA
 int hashdist = HASHDIST_DEFAULT;
 
-#ifdef CONFIG_NUMA
 static int __init set_hashdist(char *str)
 {
 	if (!str)