[PATCH v3 08/11] mm: memcontrol: constify the memcg and lruvec stat readers

[Tal Zussman]

The memcg_page_state(), memcg_events(), and lruvec_page_state()
families only read counters. Constify them.

Use container_of_const() in the lruvec_page_state() family while at it,
so the const isn't silently cast away.

Signed-off-by: Tal Zussman <tz2294@xxxxxxxxxxxx>
---
 include/linux/memcontrol.h | 23 ++++++++++++-----------
 mm/memcontrol-v1.h         |  6 +++---
 mm/memcontrol.c            | 30 +++++++++++++++---------------
 3 files changed, 30 insertions(+), 29 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 22067899eb6c..9beb065c0879 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -971,15 +971,16 @@ static inline void mod_memcg_page_state(const struct page *page,
 	rcu_read_unlock();
 }
 
-unsigned long memcg_events(struct mem_cgroup *memcg, int event);
-unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx);
-unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item);
+unsigned long memcg_events(const struct mem_cgroup *memcg, int event);
+unsigned long memcg_page_state(const struct mem_cgroup *memcg, int idx);
+unsigned long memcg_page_state_output(const struct mem_cgroup *memcg, int item);
 bool memcg_stat_item_valid(int idx);
 bool memcg_vm_event_item_valid(enum vm_event_item idx);
-unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx);
-unsigned long lruvec_page_state_monotonic(struct lruvec *lruvec,
+unsigned long lruvec_page_state(const struct lruvec *lruvec,
+				enum node_stat_item idx);
+unsigned long lruvec_page_state_monotonic(const struct lruvec *lruvec,
 					  enum node_stat_item idx);
-unsigned long lruvec_page_state_local(struct lruvec *lruvec,
+unsigned long lruvec_page_state_local(const struct lruvec *lruvec,
 				      enum node_stat_item idx);
 
 void mem_cgroup_flush_stats(struct mem_cgroup *memcg);
@@ -1412,12 +1413,12 @@ static inline void mod_memcg_page_state(const struct page *page,
 {
 }
 
-static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
+static inline unsigned long memcg_page_state(const struct mem_cgroup *memcg, int idx)
 {
 	return 0;
 }
 
-static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item)
+static inline unsigned long memcg_page_state_output(const struct mem_cgroup *memcg, int item)
 {
 	return 0;
 }
@@ -1432,19 +1433,19 @@ static inline bool memcg_vm_event_item_valid(enum vm_event_item idx)
 	return false;
 }
 
-static inline unsigned long lruvec_page_state(struct lruvec *lruvec,
+static inline unsigned long lruvec_page_state(const struct lruvec *lruvec,
 					      enum node_stat_item idx)
 {
 	return node_page_state(lruvec_pgdat(lruvec), idx);
 }
 
-static inline unsigned long lruvec_page_state_monotonic(struct lruvec *lruvec,
+static inline unsigned long lruvec_page_state_monotonic(const struct lruvec *lruvec,
 							enum node_stat_item idx)
 {
 	return node_page_state_monotonic(lruvec_pgdat(lruvec), idx);
 }
 
-static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec,
+static inline unsigned long lruvec_page_state_local(const struct lruvec *lruvec,
 						    enum node_stat_item idx)
 {
 	return node_page_state(lruvec_pgdat(lruvec), idx);
diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h
index b9a21f0fd2c3..f6d128da443e 100644
--- a/mm/memcontrol-v1.h
+++ b/mm/memcontrol-v1.h
@@ -34,9 +34,9 @@ static inline bool do_memsw_account(void)
 	return !cgroup_subsys_on_dfl(memory_cgrp_subsys);
 }
 
-unsigned long memcg_events_local(struct mem_cgroup *memcg, int event);
-unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx);
-unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item);
+unsigned long memcg_events_local(const struct mem_cgroup *memcg, int event);
+unsigned long memcg_page_state_local(const struct mem_cgroup *memcg, int idx);
+unsigned long memcg_page_state_local_output(const struct mem_cgroup *memcg, int item);
 bool memcg1_alloc_events(struct mem_cgroup *memcg);
 void memcg1_free_events(struct mem_cgroup *memcg);
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4b7c01daebce..b13f5ed74a5a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -490,9 +490,9 @@ struct lruvec_stats {
 	long state_pending[NR_MEMCG_NODE_STAT_ITEMS];
 };
 
-unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx)
+unsigned long lruvec_page_state(const struct lruvec *lruvec, enum node_stat_item idx)
 {
-	struct mem_cgroup_per_node *pn;
+	const struct mem_cgroup_per_node *pn;
 	long x;
 	int i;
 
@@ -503,7 +503,7 @@ unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx)
 	if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
 		return 0;
 
-	pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
+	pn = container_of_const(lruvec, struct mem_cgroup_per_node, lruvec);
 	x = READ_ONCE(pn->lruvec_stats->state[i]);
 #ifdef CONFIG_SMP
 	if (x < 0)
@@ -531,10 +531,10 @@ unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx)
  * monotonically-incremented event counters are stored in
  * enum node_stat_item.
  */
-unsigned long lruvec_page_state_monotonic(struct lruvec *lruvec,
+unsigned long lruvec_page_state_monotonic(const struct lruvec *lruvec,
 					  enum node_stat_item idx)
 {
-	struct mem_cgroup_per_node *pn;
+	const struct mem_cgroup_per_node *pn;
 	int i;
 
 	if (mem_cgroup_disabled())
@@ -544,14 +544,14 @@ unsigned long lruvec_page_state_monotonic(struct lruvec *lruvec,
 	if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
 		return 0;
 
-	pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
+	pn = container_of_const(lruvec, struct mem_cgroup_per_node, lruvec);
 	return (unsigned long)READ_ONCE(pn->lruvec_stats->state[i]);
 }
 
-unsigned long lruvec_page_state_local(struct lruvec *lruvec,
+unsigned long lruvec_page_state_local(const struct lruvec *lruvec,
 				      enum node_stat_item idx)
 {
-	struct mem_cgroup_per_node *pn;
+	const struct mem_cgroup_per_node *pn;
 	long x;
 	int i;
 
@@ -562,7 +562,7 @@ unsigned long lruvec_page_state_local(struct lruvec *lruvec,
 	if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
 		return 0;
 
-	pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
+	pn = container_of_const(lruvec, struct mem_cgroup_per_node, lruvec);
 	x = READ_ONCE(pn->lruvec_stats->state_local[i]);
 #ifdef CONFIG_SMP
 	if (x < 0)
@@ -827,7 +827,7 @@ static void flush_memcg_stats_dwork(struct work_struct *w)
 	queue_delayed_work(system_dfl_wq, &stats_flush_dwork, FLUSH_TIME);
 }
 
-unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
+unsigned long memcg_page_state(const struct mem_cgroup *memcg, int idx)
 {
 	long x;
 	int i = memcg_stats_index(idx);
@@ -950,7 +950,7 @@ void mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx,
 
 #ifdef CONFIG_MEMCG_V1
 /* idx can be of type enum memcg_stat_item or node_stat_item. */
-unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx)
+unsigned long memcg_page_state_local(const struct mem_cgroup *memcg, int idx)
 {
 	long x;
 	int i = memcg_stats_index(idx);
@@ -1113,7 +1113,7 @@ void count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx,
 	put_cpu();
 }
 
-unsigned long memcg_events(struct mem_cgroup *memcg, int event)
+unsigned long memcg_events(const struct mem_cgroup *memcg, int event)
 {
 	int i = memcg_events_index(event);
 
@@ -1132,7 +1132,7 @@ bool memcg_vm_event_item_valid(enum vm_event_item idx)
 }
 
 #ifdef CONFIG_MEMCG_V1
-unsigned long memcg_events_local(struct mem_cgroup *memcg, int event)
+unsigned long memcg_events_local(const struct mem_cgroup *memcg, int event)
 {
 	int i = memcg_events_index(event);
 
@@ -1715,14 +1715,14 @@ static int memcg_page_state_output_unit(int item)
 	}
 }
 
-unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item)
+unsigned long memcg_page_state_output(const struct mem_cgroup *memcg, int item)
 {
 	return memcg_page_state(memcg, item) *
 		memcg_page_state_output_unit(item);
 }
 
 #ifdef CONFIG_MEMCG_V1
-unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item)
+unsigned long memcg_page_state_local_output(const struct mem_cgroup *memcg, int item)
 {
 	return memcg_page_state_local(memcg, item) *
 		memcg_page_state_output_unit(item);

-- 
2.39.5