mm, compaction: fix build errors with kcompactd

[Arnd Bergmann]

The newly added kcompactd code introduces multiple build errors:

include/linux/compaction.h:91:12: error: 'kcompactd_run' defined but not used [-Werror=unused-function]
mm/compaction.c:1953:2: error: implicit declaration of function 'hotcpu_notifier' [-Werror=implicit-function-declaration]

This marks the new empty wrapper functions as 'inline' to avoid unused-function warnings,
and includes linux/cpu.h to get the hotcpu_notifier declaration.

Fixes: 8364acdfa45a ("mm, compaction: introduce kcompactd")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
I stumbled over this while trying out the mmots patches today for an unrelated reason.

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 1367c0564d42..d7c8de583a23 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -88,15 +88,15 @@ static inline bool compaction_deferred(struct zone *zone, int order)
 	return true;
 }
 
-static int kcompactd_run(int nid)
+static inline int kcompactd_run(int nid)
 {
 	return 0;
 }
-static void kcompactd_stop(int nid)
+static inline void kcompactd_stop(int nid)
 {
 }
 
-static void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
+static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
 {
 }
 
diff --git a/mm/compaction.c b/mm/compaction.c
index 67bb651c56b1..4cb1c2ef5abb 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -7,6 +7,7 @@
  *
  * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@xxxxxxxxx>
  */
+#include <linux/cpu.h>
 #include <linux/swap.h>
 #include <linux/migrate.h>
 #include <linux/compaction.h>