mm: page_owner: add support for splitting to any order in split page_owner

It adds a new_order parameter to set new page order in page owner. It
prepares for upcoming changes to support split huge page to any lower
order.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Zi Yan <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Acked-by: David Hildenbrand <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: Luis Chamberlain <[e-mail]>
Cc: "Matthew Wilcox (Oracle)" <[e-mail]>
Cc: Michal Koutny <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Ryan Roberts <[e-mail]>
Cc: Yang Shi <[e-mail]>
Cc: Yu Zhao <[e-mail]>
Cc: Zach O'Keefe <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/page_owner.h

···
 extern void __reset_page_owner(struct page *page, unsigned short order);
 extern void __set_page_owner(struct page *page,
 			unsigned short order, gfp_t gfp_mask);
-extern void __split_page_owner(struct page *page, int order);
+extern void __split_page_owner(struct page *page, int old_order,
+			int new_order);
 extern void __folio_copy_owner(struct folio *newfolio, struct folio *old);
 extern void __set_page_owner_migrate_reason(struct page *page, int reason);
 extern void __dump_page_owner(const struct page *page);
···
 		__set_page_owner(page, order, gfp_mask);
 }
 
-static inline void split_page_owner(struct page *page, int order)
+static inline void split_page_owner(struct page *page, int old_order,
+			int new_order)
 {
 	if (static_branch_unlikely(&page_owner_inited))
-		__split_page_owner(page, order);
+		__split_page_owner(page, old_order, new_order);
 }
 static inline void folio_copy_owner(struct folio *newfolio, struct folio *old)
 {
···
 {
 }
 static inline void set_page_owner(struct page *page,
-			unsigned int order, gfp_t gfp_mask)
+			unsigned short order, gfp_t gfp_mask)
 {
 }
-static inline void split_page_owner(struct page *page, int order)
+static inline void split_page_owner(struct page *page, int old_order,
+			int new_order)
 {
 }
 static inline void folio_copy_owner(struct folio *newfolio, struct folio *folio)

mm/huge_memory.c

···
 	unlock_page_lruvec(lruvec);
 	/* Caller disabled irqs, so they are still disabled here */
 
-	split_page_owner(head, order);
+	split_page_owner(head, order, 0);
 
 	/* See comment in __split_huge_page_tail() */
 	if (PageAnon(head)) {

mm/page_alloc.c

···
 
 	for (i = 1; i < (1 << order); i++)
 		set_page_refcounted(page + i);
-	split_page_owner(page, order);
+	split_page_owner(page, order, 0);
 	split_page_memcg(page, order, 0);
 }
 EXPORT_SYMBOL_GPL(split_page);
···
 		struct page *page = virt_to_page((void *)addr);
 		struct page *last = page + nr;
 
-		split_page_owner(page, order);
+		split_page_owner(page, order, 0);
 		split_page_memcg(page, order, 0);
 		while (page < --last)
 			set_page_refcounted(last);

mm/page_owner.c

···
 	page_ext_put(page_ext);
 }
 
-void __split_page_owner(struct page *page, int order)
+void __split_page_owner(struct page *page, int old_order, int new_order)
 {
 	int i;
 	struct page_ext *page_ext = page_ext_get(page);
 	struct page_owner *page_owner;
-	unsigned int nr = 1 << order;
 
 	if (unlikely(!page_ext))
 		return;
 
-	for (i = 0; i < nr; i++) {
+	for (i = 0; i < (1 << old_order); i++) {
 		page_owner = get_page_owner(page_ext);
-		page_owner->order = 0;
+		page_owner->order = new_order;
 		page_ext = page_ext_next(page_ext);
 	}
 	page_ext_put(page_ext);