compound pages: Add new support functions

compound_pages(page)	-> Determines base pages of a compound page

compound_shift(page)	-> Determine the page shift of a compound page

compound_size(page)	-> Determine the size of a compound page

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 include/linux/mm.h |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

Index: vps/include/linux/mm.h
===================================================================
--- vps.orig/include/linux/mm.h	2007-06-11 15:56:37.000000000 -0700
+++ vps/include/linux/mm.h	2007-06-12 19:06:28.000000000 -0700
@@ -365,6 +365,21 @@ static inline void set_compound_order(st
 	page[1].lru.prev = (void *)order;
 }
 
+static inline int compound_pages(struct page *page)
+{
+ 	return 1 << compound_order(page);
+}
+
+static inline int compound_shift(struct page *page)
+{
+ 	return PAGE_SHIFT + compound_order(page);
+}
+
+static inline int compound_size(struct page *page)
+{
+	return PAGE_SIZE << compound_order(page);
+}
+
 /*
  * Multiple processes may "see" the same page. E.g. for untouched
  * mappings of /dev/null, all processes see the same page full of