[RFC PATCH 2/5] mm: page_owner: add support for splitting to any order in split page_owner.

[Zi Yan <zi.yan@sent.com>]

From: Zi Yan <ziy@nvidia.com>

It adds a new_order parameter to set new page order in page owner and
uses old_order instead of nr to make the parameters look consistent.
It prepares for upcoming changes to support split huge page to any
lower order.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 include/linux/page_owner.h | 12 +++++++-----
 mm/huge_memory.c           |  3 ++-
 mm/page_alloc.c            |  2 +-
 mm/page_owner.c            | 13 +++++++------
 4 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index 119a0c9d2a8b..16050cc89274 100644
--- a/include/linux/page_owner.h
+++ b/include/linux/page_owner.h
@@ -11,7 +11,8 @@ extern struct page_ext_operations page_owner_ops;
 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, unsigned int nr);
+extern void __split_page_owner(struct page *page, unsigned short old_order,
+			unsigned short 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);
@@ -31,10 +32,11 @@ static inline void set_page_owner(struct page *page,
 		__set_page_owner(page, order, gfp_mask);
 }
 
-static inline void split_page_owner(struct page *page, unsigned int nr)
+static inline void split_page_owner(struct page *page, unsigned int old_order,
+			unsigned int new_order)
 {
 	if (static_branch_unlikely(&page_owner_inited))
-		__split_page_owner(page, nr);
+		__split_page_owner(page, old_order, new_order);
 }
 static inline void folio_copy_owner(struct folio *newfolio, struct folio *old)
 {
@@ -56,11 +58,11 @@ static inline void reset_page_owner(struct page *page, unsigned short order)
 {
 }
 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,
-			unsigned short order)
+			unsigned short old_order, unsigned short new_order)
 {
 }
 static inline void folio_copy_owner(struct folio *newfolio, struct folio *folio)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 640040c386f0..fcfa46af6c4c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2367,6 +2367,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	struct lruvec *lruvec;
 	struct address_space *swap_cache = NULL;
 	unsigned long offset = 0;
+	unsigned int order = thp_order(head);
 	unsigned int nr = thp_nr_pages(head);
 	int i;
 
@@ -2408,7 +2409,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	unlock_page_lruvec(lruvec);
 	/* Caller disabled irqs, so they are still disabled here */
 
-	split_page_owner(head, nr);
+	split_page_owner(head, order, 0);
 
 	/* See comment in __split_huge_page_tail() */
 	if (PageAnon(head)) {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d982919b9e51..9cac40c26c58 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3514,7 +3514,7 @@ void split_page(struct page *page, unsigned int order)
 
 	for (i = 1; i < (1 << order); i++)
 		set_page_refcounted(page + i);
-	split_page_owner(page, 1 << order);
+	split_page_owner(page, order, 0);
 	split_page_memcg(page, 1 << order, 0);
 }
 EXPORT_SYMBOL_GPL(split_page);
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 0a9588506571..52013c846d19 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -202,19 +202,20 @@ void __set_page_owner_migrate_reason(struct page *page, int reason)
 	page_owner->last_migrate_reason = reason;
 }
 
-void __split_page_owner(struct page *page, unsigned int nr)
+void __split_page_owner(struct page *page, unsigned short old_order,
+			unsigned short new_order)
 {
-	int i;
-	struct page_ext *page_ext = lookup_page_ext(page);
+	int i, old_nr = 1 << old_order, new_nr = 1 << new_order;
+	struct page_ext *page_ext;
 	struct page_owner *page_owner;
 
 	if (unlikely(!page_ext))
 		return;
 
-	for (i = 0; i < nr; i++) {
+	for (i = 0; i < old_nr; i += new_nr) {
+		page_ext = lookup_page_ext(page + i);
 		page_owner = get_page_owner(page_ext);
-		page_owner->order = 0;
-		page_ext = page_ext_next(page_ext);
+		page_owner->order = new_order;
 	}
 }
 
-- 
2.35.1