[PATCH 1/4] pull out the page pre-release and sanity check logic for reuse

[Andy Whitcroft <apw@shadowen.org>]

When we are about to release a page we perform a number of actions
on that page.  We clear down any anonymous mappings, confirm that
the page is safe to release, check for freeing locks, before mapping
the page should that be required.  Pull this processing out into a
helper function for reuse in a later patch.

Note that we do not convert the similar cleardown in free_hot_cold_page()
as the optimiser is unable to squash the loops during the inline.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
---
 mm/page_alloc.c |   43 ++++++++++++++++++++++++++++++-------------
 1 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8aa93f3..758ecf1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -468,6 +468,35 @@ static inline int free_pages_check(struct page *page)
 }
 
 /*
+ * Prepare this page for release to the buddy.  Sanity check the page.
+ * Returns 1 if the page is safe to free.
+ */
+static inline int free_page_prepare(struct page *page, int order)
+{
+	int i;
+	int reserved = 0;
+
+	if (PageAnon(page))
+		page->mapping = NULL;
+
+	for (i = 0 ; i < (1 << order) ; ++i)
+		reserved += free_pages_check(page + i);
+	if (reserved)
+		return 0;
+
+	if (!PageHighMem(page)) {
+		debug_check_no_locks_freed(page_address(page),
+							PAGE_SIZE << order);
+		debug_check_no_obj_freed(page_address(page),
+					   PAGE_SIZE << order);
+	}
+	arch_free_page(page, order);
+	kernel_map_pages(page, 1 << order, 0);
+
+	return 1;
+}
+
+/*
  * Frees a list of pages. 
  * Assumes all pages on list are in same zone, and of same order.
  * count is the number of pages to free.
@@ -508,22 +537,10 @@ static void free_one_page(struct zone *zone, struct page *page, int order)
 static void __free_pages_ok(struct page *page, unsigned int order)
 {
 	unsigned long flags;
-	int i;
-	int reserved = 0;
 
-	for (i = 0 ; i < (1 << order) ; ++i)
-		reserved += free_pages_check(page + i);
-	if (reserved)
+	if (!free_page_prepare(page, order))
 		return;
 
-	if (!PageHighMem(page)) {
-		debug_check_no_locks_freed(page_address(page),PAGE_SIZE<<order);
-		debug_check_no_obj_freed(page_address(page),
-					   PAGE_SIZE << order);
-	}
-	arch_free_page(page, order);
-	kernel_map_pages(page, 1 << order, 0);
-
 	local_irq_save(flags);
 	__count_vm_events(PGFREE, 1 << order);
 	free_one_page(page_zone(page), page, order);
-- 
1.5.6.1.201.g3e7d3