[PATCH v4 3/7] mm: memcg: make memcg huge page split support any order split.

[Zi Yan <zi.yan@xxxxxxxx>]

From: Zi Yan <ziy@xxxxxxxxxx>

It sets memcg information for the pages after the split. A new parameter
new_order is added to tell the order of subpages in the new page, always 0
for now. It prepares for upcoming changes to support split huge page to
any lower order.

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 include/linux/memcontrol.h |  4 ++--
 mm/huge_memory.c           |  2 +-
 mm/memcontrol.c            | 11 ++++++-----
 mm/page_alloc.c            |  4 ++--
 4 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 173bbb53c1ec..9a2dea92be0e 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1163,7 +1163,7 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm,
 	rcu_read_unlock();
 }
 
-void split_page_memcg(struct page *head, int order);
+void split_page_memcg(struct page *head, int old_order, int new_order);
 
 unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
 						gfp_t gfp_mask,
@@ -1621,7 +1621,7 @@ void count_memcg_event_mm(struct mm_struct *mm, enum vm_event_item idx)
 {
 }
 
-static inline void split_page_memcg(struct page *head, int order)
+static inline void split_page_memcg(struct page *head, int old_order, int new_order)
 {
 }
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f079b02f1f59..3d30eccd3a7f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2880,7 +2880,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	int order = folio_order(folio);
 
 	/* complete memcg works before add pages to LRU */
-	split_page_memcg(head, order);
+	split_page_memcg(head, order, 0);
 
 	if (folio_test_anon(folio) && folio_test_swapcache(folio)) {
 		offset = swp_offset(folio->swap);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 404e529644c0..27d53715d8dc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3608,23 +3608,24 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
 /*
  * Because page_memcg(head) is not set on tails, set it now.
  */
-void split_page_memcg(struct page *head, int order)
+void split_page_memcg(struct page *head, int old_order, int new_order)
 {
 	struct folio *folio = page_folio(head);
 	struct mem_cgroup *memcg = folio_memcg(folio);
 	int i;
-	unsigned int nr = 1 << order;
+	unsigned int old_nr = 1 << old_order;
+	unsigned int new_nr = 1 << new_order;
 
 	if (mem_cgroup_disabled() || !memcg)
 		return;
 
-	for (i = 1; i < nr; i++)
+	for (i = new_nr; i < old_nr; i += new_nr)
 		folio_page(folio, i)->memcg_data = folio->memcg_data;
 
 	if (folio_memcg_kmem(folio))
-		obj_cgroup_get_many(__folio_objcg(folio), nr - 1);
+		obj_cgroup_get_many(__folio_objcg(folio), old_nr / new_nr - 1);
 	else
-		css_get_many(&memcg->css, nr - 1);
+		css_get_many(&memcg->css, old_nr / new_nr - 1);
 }
 
 #ifdef CONFIG_SWAP
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b6e8fe6fed67..9d4dd41d0647 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2653,7 +2653,7 @@ 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, order);
-	split_page_memcg(page, order);
+	split_page_memcg(page, order, 0);
 }
 EXPORT_SYMBOL_GPL(split_page);
 
@@ -4838,7 +4838,7 @@ static void *make_alloc_exact(unsigned long addr, unsigned int order,
 		struct page *last = page + nr;
 
 		split_page_owner(page, order);
-		split_page_memcg(page, order);
+		split_page_memcg(page, order, 0);
 		while (page < --last)
 			set_page_refcounted(last);
 
-- 
2.43.0