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/[email protected]
Signed-off-by: Joonsoo Kim <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f07552f..a82b303 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2461,7 +2461,6 @@
 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 @@
 		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);