From: Peter Zijlstra <a.p.zijlstra@chello.nl> 
Subject: [PATCH 04/31] mm: tag reseve pages
Patch-mainline: not yet

Tag pages allocated from the reserves with a non-zero page->reserve.
This allows us to distinguish and account reserve pages.

Since low-memory situations are transient, and unrelated the the actual
page (any page can be on the freelist when we run low), don't mark the
page in any permanent way - just pass along the information to the
allocatee.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
---
 include/linux/mm_types.h |    1 +
 mm/page_alloc.c          |    4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -71,6 +71,7 @@ struct page {
 	union {
 		pgoff_t index;		/* Our offset within mapping. */
 		void *freelist;		/* SLUB: freelist req. slab lock */
+		int reserve;		/* page_alloc: page is a reserve page */
 	};
 	struct list_head lru;		/* Pageout list, eg. active_list
 					 * protected by zone->lru_lock !
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1656,8 +1656,10 @@ zonelist_scan:
 try_this_zone:
 		page = buffered_rmqueue(preferred_zone, zone, order,
 						gfp_mask, migratetype);
-		if (page)
+		if (page) {
+			page->reserve = !!(alloc_flags & ALLOC_NO_WATERMARKS);
 			break;
+		}
 this_zone_full:
 		if (NUMA_BUILD)
 			zlc_mark_zone_full(zonelist, z);
