mm: page_alloc: use get_freepage_migratetype() instead of page_private()

The page allocator uses set_page_private and page_private for handling
migratetype when it frees page.  Let's replace them with [set|get]
_freepage_migratetype to make it more clear.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -237,6 +237,18 @@ struct inode;
 #define page_private(page)		((page)->private)
 #define set_page_private(page, v)	((page)->private = (v))
 
+/* It's valid only if the page is free path or free_list */
+static inline void set_freepage_migratetype(struct page *page, int migratetype)
+{
+	set_page_private(page, migratetype);
+}
+
+/* It's valid only if the page is free path or free_list */
+static inline int get_freepage_migratetype(struct page *page)
+{
+	return page_private(page);
+}
+
 /*
  * FIXME: take this include out, include page-flags.h in
  * files which need it (119 of them)

mm/page_alloc.c

@@ -674,7 +674,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
 			page = list_entry(list->prev, struct page, lru);
 			/* must delete as __free_one_page list manipulates */
 			list_del(&page->lru);
-			mt = page_private(page);
+			mt = get_freepage_migratetype(page);
 			/* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
 			__free_one_page(page, zone, 0, mt);
 			trace_mm_page_pcpu_drain(page, 0, mt);
@@ -1143,7 +1143,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
 			if (!is_migrate_cma(mt) && mt != MIGRATE_ISOLATE)
 				mt = migratetype;
 		}
-		set_page_private(page, mt);
+		set_freepage_migratetype(page, mt);
 		list = &page->lru;
 		if (is_migrate_cma(mt))
 			__mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
@@ -1313,7 +1313,7 @@ void free_hot_cold_page(struct page *page, int cold)
 		return;
 
 	migratetype = get_pageblock_migratetype(page);
-	set_page_private(page, migratetype);
+	set_freepage_migratetype(page, migratetype);
 	local_irq_save(flags);
 	if (unlikely(wasMlocked))
 		free_page_mlock(page);

mm/page_isolation.c

@@ -203,7 +203,7 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn)
 		if (PageBuddy(page))
 			pfn += 1 << page_order(page);
 		else if (page_count(page) == 0 &&
-				page_private(page) == MIGRATE_ISOLATE)
+			get_freepage_migratetype(page) == MIGRATE_ISOLATE)
 			pfn += 1;
 		else
 			break;