2 files changed, 12 insertions, 8 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 083cc0ba2384..4310f80ce956 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1313,6 +1313,7 @@ extern void free_initmem(void);
  */
 extern unsigned long free_reserved_area(void *start, void *end,
                                         int poison, char *s);
+
 #ifdef  CONFIG_HIGHMEM
 /*
  * Free a highmem page into the buddy system, adjusting totalhigh_pages
@@ -1321,10 +1322,7 @@ extern unsigned long free_reserved_area(void *start, void *end,
 extern void free_highmem_page(struct page *page);
 #endif
 
-static inline void adjust_managed_page_count(struct page *page, long count)
-{
-        totalram_pages += count;
-}
+extern void adjust_managed_page_count(struct page *page, long count);
 
 /* Free the reserved page into the buddy system, so it gets managed. */
 static inline void __free_reserved_page(struct page *page)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e511f9429f1e..09d381b71fd8 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -474,10 +474,16 @@ struct zone {
          * frequently read in proximity to zone->lock.  It's good to
          * give them a chance of being in the same cacheline.
          *
-         * Write access to present_pages and managed_pages at runtime should
-         * be protected by lock_memory_hotplug()/unlock_memory_hotplug().
-         * Any reader who can't tolerant drift of present_pages and
-         * managed_pages should hold memory hotplug lock to get a stable value.
+         * Write access to present_pages at runtime should be protected by
+         * lock_memory_hotplug()/unlock_memory_hotplug().  Any reader who can't
+         * tolerant drift of present_pages should hold memory hotplug lock to
+         * get a stable value.
+         *
+         * Read access to managed_pages should be safe because it's unsigned
+         * long. Write access to zone->managed_pages and totalram_pages are
+         * protected by managed_page_count_lock at runtime. Idealy only
+         * adjust_managed_page_count() should be used instead of directly
+         * touching zone->managed_pages and totalram_pages.
          */
         unsigned long           spanned_pages;
         unsigned long           present_pages;