mm/page_owner: introduce split_page_owner and replace manual handling

split_page() calls set_page_owner() to set up page_owner to each pages.
But, it has a drawback that head page and the others have different
stacktrace because callsite of set_page_owner() is slightly differnt.
To avoid this problem, this patch copies head page's page_owner to the
others.  It needs to introduce new function, split_page_owner() but it
also remove the other function, get_page_owner_gfp() so looks good to
do.

Link: http://lkml.kernel.org/r/1464230275-25791-4-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/page_owner.h

@@ -10,7 +10,7 @@ extern struct page_ext_operations page_owner_ops;
 extern void __reset_page_owner(struct page *page, unsigned int order);
 extern void __set_page_owner(struct page *page,
 			unsigned int order, gfp_t gfp_mask);
-extern gfp_t __get_page_owner_gfp(struct page *page);
+extern void __split_page_owner(struct page *page, unsigned int order);
 extern void __copy_page_owner(struct page *oldpage, struct page *newpage);
 extern void __set_page_owner_migrate_reason(struct page *page, int reason);
 extern void __dump_page_owner(struct page *page);
@@ -28,12 +28,10 @@ static inline void set_page_owner(struct page *page,
 		__set_page_owner(page, order, gfp_mask);
 }
 
-static inline gfp_t get_page_owner_gfp(struct page *page)
+static inline void split_page_owner(struct page *page, unsigned int order)
 {
 	if (static_branch_unlikely(&page_owner_inited))
-		return __get_page_owner_gfp(page);
-	else
-		return 0;
+		__split_page_owner(page, order);
 }
 static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
 {
@@ -58,9 +56,9 @@ static inline void set_page_owner(struct page *page,
 			unsigned int order, gfp_t gfp_mask)
 {
 }
-static inline gfp_t get_page_owner_gfp(struct page *page)
+static inline void split_page_owner(struct page *page,
+			unsigned int order)
 {
-	return 0;
 }
 static inline void copy_page_owner(struct page *oldpage, struct page *newpage)
 {

mm/page_alloc.c

@@ -2461,7 +2461,6 @@ void free_hot_cold_page_list(struct list_head *list, bool cold)
 void split_page(struct page *page, unsigned int order)
 {
 	int i;
-	gfp_t gfp_mask;
 
 	VM_BUG_ON_PAGE(PageCompound(page), page);
 	VM_BUG_ON_PAGE(!page_count(page), page);
@@ -2475,12 +2474,9 @@ void split_page(struct page *page, unsigned int order)
 		split_page(virt_to_page(page[0].shadow), order);
 #endif
 
-	gfp_mask = get_page_owner_gfp(page);
-	set_page_owner(page, 0, gfp_mask);
-	for (i = 1; i < (1 << order); i++) {
+	for (i = 1; i < (1 << order); i++)
 		set_page_refcounted(page + i);
-		set_page_owner(page + i, 0, gfp_mask);
-	}
+	split_page_owner(page, order);
 }
 EXPORT_SYMBOL_GPL(split_page);
 

mm/page_owner.c

@@ -94,17 +94,17 @@ void __set_page_owner_migrate_reason(struct page *page, int reason)
 	page_ext->last_migrate_reason = reason;
 }
 
-gfp_t __get_page_owner_gfp(struct page *page)
+void __split_page_owner(struct page *page, unsigned int order)
 {
+	int i;
 	struct page_ext *page_ext = lookup_page_ext(page);
-	if (unlikely(!page_ext))
-		/*
-		 * The caller just returns 0 if no valid gfp
-		 * So return 0 here too.
-		 */
-		return 0;
 
-	return page_ext->gfp_mask;
+	if (unlikely(!page_ext))
+		return;
+
+	page_ext->order = 0;
+	for (i = 1; i < (1 << order); i++)
+		__copy_page_owner(page, page + i);
 }
 
 void __copy_page_owner(struct page *oldpage, struct page *newpage)