[PATCH v9 4/7] mm: Change count_objcg_event() to count_objcg_events() for batch event updates.

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

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().

To facilitate this, the existing count_objcg_event() API is modified
to be count_objcg_events() that additionally accepts a count parameter.
The only existing calls to count_objcg_event() are in zswap.c - these
have been modified to call count_objcg_events() with a count of 1.

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
---
 include/linux/memcontrol.h | 12 +++++++-----
 mm/zswap.c                 |  6 +++---
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 15c2716f9aa3..524006313b0d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1764,8 +1764,9 @@ static inline int memcg_kmem_id(struct mem_cgroup *memcg)
 
 struct mem_cgroup *mem_cgroup_from_slab_obj(void *p);
 
-static inline void count_objcg_event(struct obj_cgroup *objcg,
-				     enum vm_event_item idx)
+static inline void count_objcg_events(struct obj_cgroup *objcg,
+				      enum vm_event_item idx,
+				      unsigned long count)
 {
 	struct mem_cgroup *memcg;
 
@@ -1774,7 +1775,7 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 
 	rcu_read_lock();
 	memcg = obj_cgroup_memcg(objcg);
-	count_memcg_events(memcg, idx, 1);
+	count_memcg_events(memcg, idx, count);
 	rcu_read_unlock();
 }
 
@@ -1829,8 +1830,9 @@ static inline struct mem_cgroup *mem_cgroup_from_slab_obj(void *p)
 	return NULL;
 }
 
-static inline void count_objcg_event(struct obj_cgroup *objcg,
-				     enum vm_event_item idx)
+static inline void count_objcg_events(struct obj_cgroup *objcg,
+				      enum vm_event_item idx,
+				      unsigned long count)
 {
 }
 
diff --git a/mm/zswap.c b/mm/zswap.c
index 0f281e50a034..69b9c025fd47 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1053,7 +1053,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 
 	count_vm_event(ZSWPWB);
 	if (entry->objcg)
-		count_objcg_event(entry->objcg, ZSWPWB);
+		count_objcg_events(entry->objcg, ZSWPWB, 1);
 
 	zswap_entry_free(entry);
 
@@ -1482,7 +1482,7 @@ bool zswap_store(struct folio *folio)
 
 	if (objcg) {
 		obj_cgroup_charge_zswap(objcg, entry->length);
-		count_objcg_event(objcg, ZSWPOUT);
+		count_objcg_events(objcg, ZSWPOUT, 1);
 	}
 
 	/*
@@ -1576,7 +1576,7 @@ bool zswap_load(struct folio *folio)
 
 	count_vm_event(ZSWPIN);
 	if (entry->objcg)
-		count_objcg_event(entry->objcg, ZSWPIN);
+		count_objcg_events(entry->objcg, ZSWPIN, 1);
 
 	if (swapcache) {
 		zswap_entry_free(entry);
-- 
2.27.0