[RFC PATCH 2/6] mm: memcg: make memcg huge page split support any order split.

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

From: Zi Yan <ziy@nvidia.com>

It reads thp_nr_pages and splits to provided new_nr. It prepares for
upcoming changes to support split huge page to any lower order.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 include/linux/memcontrol.h | 5 +++--
 mm/huge_memory.c           | 2 +-
 mm/memcontrol.c            | 4 ++--
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0f4dd7829fb2..b3bac79ceed6 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1105,7 +1105,7 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm,
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-void mem_cgroup_split_huge_fixup(struct page *head);
+void mem_cgroup_split_huge_fixup(struct page *head, unsigned int new_nr);
 #endif
 
 #else /* CONFIG_MEMCG */
@@ -1451,7 +1451,8 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
 	return 0;
 }
 
-static inline void mem_cgroup_split_huge_fixup(struct page *head)
+static inline void mem_cgroup_split_huge_fixup(struct page *head,
+					       unsigned int new_nr)
 {
 }
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c4fead5ead31..f599f5b9bf7f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2429,7 +2429,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	lruvec = mem_cgroup_page_lruvec(head, pgdat);
 
 	/* complete memcg works before add pages to LRU */
-	mem_cgroup_split_huge_fixup(head);
+	mem_cgroup_split_huge_fixup(head, 1);
 
 	if (PageAnon(head) && PageSwapCache(head)) {
 		swp_entry_t entry = { .val = page_private(head) };
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 33f632689cee..e9705ba6bbcc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3247,7 +3247,7 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
  * Because tail pages are not marked as "used", set it. We're under
  * pgdat->lru_lock and migration entries setup in all page mappings.
  */
-void mem_cgroup_split_huge_fixup(struct page *head)
+void mem_cgroup_split_huge_fixup(struct page *head, unsigned int new_nr)
 {
 	struct mem_cgroup *memcg = page_memcg(head);
 	int i;
@@ -3255,7 +3255,7 @@ void mem_cgroup_split_huge_fixup(struct page *head)
 	if (mem_cgroup_disabled())
 		return;
 
-	for (i = 1; i < thp_nr_pages(head); i++) {
+	for (i = new_nr; i < thp_nr_pages(head); i += new_nr) {
 		css_get(&memcg->css);
 		head[i].memcg_data = (unsigned long)memcg;
 	}
-- 
2.28.0