Breakout page_order() to internal.h to avoid special knowledge of the buddy allocator

The statistics patch later needs to know what order a free page is on the free
lists.  Rather than having special knowledge of page_private() when
PageBuddy() is set, this patch places out page_order() in internal.h and adds
a VM_BUG_ON to catch using it on non-PageBuddy pages.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/mm/internal.h b/mm/internal.h
index a3110c02aea7..953f941ea867 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -37,4 +37,14 @@ static inline void __put_page(struct page *page)
 extern void fastcall __init __free_pages_bootmem(struct page *page,
                                                 unsigned int order);
 
+/*
+ * function for dealing with page's order in buddy system.
+ * zone->lock is already acquired when we use these.
+ * So, we don't need atomic page->flags operations here.
+ */
+static inline unsigned long page_order(struct page *page)
+{
+        VM_BUG_ON(!PageBuddy(page));
+        return page_private(page);
+}
 #endif