[PATCH v8 4/8] mm: Provide a new count_objcg_events() API for batch event updates.

[Kanchana P Sridhar <kanchana.p.sridhar@intel.com>]

With the introduction of zswap_store() swapping out large folios,
we need to efficiently update the objcg's memcg events once per
successfully stored folio. For instance, the 'ZSWPOUT' event needs
to be incremented by folio_nr_pages().

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
---
 include/linux/memcontrol.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 15c2716f9aa3..f47fd00c5eea 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1778,6 +1778,21 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 	rcu_read_unlock();
 }
 
+static inline void count_objcg_events(struct obj_cgroup *objcg,
+				      enum vm_event_item idx,
+				      unsigned long count)
+{
+	struct mem_cgroup *memcg;
+
+	if (!memcg_kmem_online())
+		return;
+
+	rcu_read_lock();
+	memcg = obj_cgroup_memcg(objcg);
+	count_memcg_events(memcg, idx, count);
+	rcu_read_unlock();
+}
+
 #else
 static inline bool mem_cgroup_kmem_disabled(void)
 {
@@ -1834,6 +1849,11 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 {
 }
 
+static inline void count_objcg_events(struct obj_cgroup *objcg,
+				      enum vm_event_item idx,
+				      unsigned long count)
+{
+}
 #endif /* CONFIG_MEMCG */
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP)
-- 
2.27.0