[PATCH v3 1/3] mm: memcontrol: correct the type of stats_updates to unsigned long

[Qi Zheng]

From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>

The memcg_rstat_updated() tracks updates for vmstats_percpu->state
and lruvec_stats_percpu->state. Since these state values are of type long,
change the val parameter passed to memcg_rstat_updated() to long as well.

Correspondingly, change the type of stats_updates in struct
memcg_vmstats_percpu and struct memcg_vmstats from unsigned int and
atomic_t to unsigned long and atomic_long_t respectively to prevent
potential overflow when handling large state updates during the
reparenting of LRU folios.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx>
---
 mm/memcontrol.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ac7b46c4d67e4..3daab9b46429a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -608,7 +608,7 @@ static inline int memcg_events_index(enum vm_event_item idx)
 
 struct memcg_vmstats_percpu {
 	/* Stats updates since the last flush */
-	unsigned int			stats_updates;
+	unsigned long			stats_updates;
 
 	/* Cached pointers for fast iteration in memcg_rstat_updated() */
 	struct memcg_vmstats_percpu __percpu	*parent_pcpu;
@@ -639,7 +639,7 @@ struct memcg_vmstats {
 	unsigned long		events_pending[NR_MEMCG_EVENTS];
 
 	/* Stats updates since the last flush */
-	atomic_t		stats_updates;
+	atomic_long_t		stats_updates;
 };
 
 /*
@@ -665,16 +665,16 @@ static u64 flush_last_time;
 
 static bool memcg_vmstats_needs_flush(struct memcg_vmstats *vmstats)
 {
-	return atomic_read(&vmstats->stats_updates) >
+	return atomic_long_read(&vmstats->stats_updates) >
 		MEMCG_CHARGE_BATCH * num_online_cpus();
 }
 
-static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val,
+static inline void memcg_rstat_updated(struct mem_cgroup *memcg, long val,
 				       int cpu)
 {
 	struct memcg_vmstats_percpu __percpu *statc_pcpu;
 	struct memcg_vmstats_percpu *statc;
-	unsigned int stats_updates;
+	unsigned long stats_updates;
 
 	if (!val)
 		return;
@@ -697,7 +697,7 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val,
 			continue;
 
 		stats_updates = this_cpu_xchg(statc_pcpu->stats_updates, 0);
-		atomic_add(stats_updates, &statc->vmstats->stats_updates);
+		atomic_long_add(stats_updates, &statc->vmstats->stats_updates);
 	}
 }
 
@@ -705,7 +705,7 @@ static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force)
 {
 	bool needs_flush = memcg_vmstats_needs_flush(memcg->vmstats);
 
-	trace_memcg_flush_stats(memcg, atomic_read(&memcg->vmstats->stats_updates),
+	trace_memcg_flush_stats(memcg, atomic_long_read(&memcg->vmstats->stats_updates),
 		force, needs_flush);
 
 	if (!force && !needs_flush)
@@ -4446,8 +4446,8 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu)
 	}
 	WRITE_ONCE(statc->stats_updates, 0);
 	/* We are in a per-cpu loop here, only do the atomic write once */
-	if (atomic_read(&memcg->vmstats->stats_updates))
-		atomic_set(&memcg->vmstats->stats_updates, 0);
+	if (atomic_long_read(&memcg->vmstats->stats_updates))
+		atomic_long_set(&memcg->vmstats->stats_updates, 0);
 }
 
 static void mem_cgroup_fork(struct task_struct *task)
-- 
2.20.1