[PATCH v2 1/4] mm: memcontrol: correct the type of stats_updates to unsigned long

Qi Zheng
2026-03-25T14:14:08Z

From: Qi Zheng <zhengqi.arch@bytedance.com>

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@bytedance.com>
---
mm/memcontrol.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a47fb68dd65f1..7fb9cbc10dfbb 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)
@@ -4406,8 +4406,8 @@ 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