mm/memcontrol: support MEMORY_DEVICE_PRIVATE

HMM pages (private or public device pages) are ZONE_DEVICE page and thus
need special handling when it comes to lru or refcount.  This patch make
sure that memcontrol properly handle those when it face them.  Those pages
are use like regular pages in a process address space either as anonymous
page or as file back page.  So from memcg point of view we want to handle
them like regular page for now at least.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jérôme Glisse <[email protected]>
Acked-by: Balbir Singh <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Aneesh Kumar <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: David Nellans <[email protected]>
Cc: Evgeny Baskakov <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Mark Hairgrove <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Sherry Cheung <[email protected]>
Cc: Subhash Gutti <[email protected]>
Cc: Bob Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/memremap.c

@@ -516,6 +516,7 @@ void put_zone_device_private_page(struct page *page)
 		__ClearPageWaiters(page);
 
 		page->mapping = NULL;
+		mem_cgroup_uncharge(page);
 
 		page->pgmap->page_free(page, page->pgmap->data);
 	} else if (!count)