mm: introduce free_pages_prepare()

free_hot_cold_page() and __free_pages_ok() have very similar freeing
preparation.  Consolidate them.

[akpm@linux-foundation.org: fix busted coding style]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -620,20 +620,23 @@ static void free_one_page(struct zone *zone, struct page *page, int order,
 	spin_unlock(&zone->lock);
 }
 
-static void __free_pages_ok(struct page *page, unsigned int order)
+static bool free_pages_prepare(struct page *page, unsigned int order)
 {
-	unsigned long flags;
 	int i;
 	int bad = 0;
-	int wasMlocked = __TestClearPageMlocked(page);
 
 	trace_mm_page_free_direct(page, order);
 	kmemcheck_free_shadow(page, order);
 
-	for (i = 0 ; i < (1 << order) ; ++i)
-		bad += free_pages_check(page + i);
+	for (i = 0; i < (1 << order); i++) {
+		struct page *pg = page + i;
+
+		if (PageAnon(pg))
+			pg->mapping = NULL;
+		bad += free_pages_check(pg);
+	}
 	if (bad)
-		return;
+		return false;
 
 	if (!PageHighMem(page)) {
 		debug_check_no_locks_freed(page_address(page),PAGE_SIZE<<order);
@@ -643,6 +646,17 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 	arch_free_page(page, order);
 	kernel_map_pages(page, 1 << order, 0);
 
+	return true;
+}
+
+static void __free_pages_ok(struct page *page, unsigned int order)
+{
+	unsigned long flags;
+	int wasMlocked = __TestClearPageMlocked(page);
+
+	if (!free_pages_prepare(page, order))
+		return;
+
 	local_irq_save(flags);
 	if (unlikely(wasMlocked))
 		free_page_mlock(page);
@@ -1128,21 +1142,9 @@ void free_hot_cold_page(struct page *page, int cold)
 	int migratetype;
 	int wasMlocked = __TestClearPageMlocked(page);
 
-	trace_mm_page_free_direct(page, 0);
-	kmemcheck_free_shadow(page, 0);
-
-	if (PageAnon(page))
-		page->mapping = NULL;
-	if (free_pages_check(page))
+	if (!free_pages_prepare(page, 0))
 		return;
 
-	if (!PageHighMem(page)) {
-		debug_check_no_locks_freed(page_address(page), PAGE_SIZE);
-		debug_check_no_obj_freed(page_address(page), PAGE_SIZE);
-	}
-	arch_free_page(page, 0);
-	kernel_map_pages(page, 1, 0);
-
 	migratetype = get_pageblock_migratetype(page);
 	set_page_private(page, migratetype);
 	local_irq_save(flags);