Re: [PATCH v2 2/4] mm: memcontrol: change val type to long in __mod_memcg_{lruvec_}state()

Lorenzo Stoakes (Oracle)
2026-03-26T09:19:41Z

On Wed, Mar 25, 2026 at 10:13:23PM +0800, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@bytedance.com>
>
> The __mod_memcg_state() and __mod_memcg_lruvec_state() functions are also
> used to reparent non-hierarchical stats. In this scenario, the values
> passed to them are accumulated statistics that might be extremely large
> and exceed the upper limit of a 32-bit integer.
>
> Change the val parameter type from int to long in these functions and
> their corresponding tracepoints (memcg_rstat_stats) to prevent potential
> overflow issues.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>

LGTM, so:

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>

> ---
> include/trace/events/memcg.h | 10 +++++-----
> mm/memcontrol.c | 8 ++++----
> 2 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/include/trace/events/memcg.h b/include/trace/events/memcg.h
> index dfe2f51019b4c..51b62c5931fc2 100644
> --- a/include/trace/events/memcg.h
> +++ b/include/trace/events/memcg.h
> @@ -11,14 +11,14 @@
>
> DECLARE_EVENT_CLASS(memcg_rstat_stats,
>
> - TP_PROTO(struct mem_cgroup *memcg, int item, int val),
> + TP_PROTO(struct mem_cgroup *memcg, int item, long val),
>
> TP_ARGS(memcg, item, val),
>
> TP_STRUCT__entry(
> __field(u64, id)
> __field(int, item)
> - __field(int, val)
> + __field(long, val)
> ),
>
> TP_fast_assign(
> @@ -27,20 +27,20 @@ DECLARE_EVENT_CLASS(memcg_rstat_stats,
> __entry->val = val;
> ),
>
> - TP_printk("memcg_id=%llu item=%d val=%d",
> + TP_printk("memcg_id=%llu item=%d val=%ld",
> __entry->id, __entry->item, __entry->val)
> );
>
> DEFINE_EVENT(memcg_rstat_stats, mod_memcg_state,
>
> - TP_PROTO(struct mem_cgroup *memcg, int item, int val),
> + TP_PROTO(struct mem_cgroup *memcg, int item, long val),
>
> TP_ARGS(memcg, item, val)
> );
>
> DEFINE_EVENT(memcg_rstat_stats, mod_memcg_lruvec_state,
>
> - TP_PROTO(struct mem_cgroup *memcg, int item, int val),
> + TP_PROTO(struct mem_cgroup *memcg, int item, long val),
>
> TP_ARGS(memcg, item, val)
> );
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 7fb9cbc10dfbb..4a78550f6174e 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -527,7 +527,7 @@ unsigned long lruvec_page_state_local(struct lruvec *lruvec,
>
> #ifdef CONFIG_MEMCG_V1
> static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node *pn,
> - enum node_stat_item idx, int val);
> + enum node_stat_item idx, long val);
>
> void reparent_memcg_lruvec_state_local(struct mem_cgroup *memcg,
> struct mem_cgroup *parent, int idx)
> @@ -784,7 +784,7 @@ static int memcg_page_state_unit(int item);
> * Normalize the value passed into memcg_rstat_updated() to be in pages. Round
> * up non-zero sub-page updates to 1 page as zero page updates are ignored.
> */
> -static int memcg_state_val_in_pages(int idx, int val)
> +static long memcg_state_val_in_pages(int idx, long val)
> {
> int unit = memcg_page_state_unit(idx);
>
> @@ -831,7 +831,7 @@ static inline void get_non_dying_memcg_end(void)
> #endif
>
> static void __mod_memcg_state(struct mem_cgroup *memcg,
> - enum memcg_stat_item idx, int val)
> + enum memcg_stat_item idx, long val)
> {
> int i = memcg_stats_index(idx);
> int cpu;
> @@ -896,7 +896,7 @@ void reparent_memcg_state_local(struct mem_cgroup *memcg,
> #endif
>
> static void __mod_memcg_lruvec_state(struct mem_cgroup_per_node *pn,
> - enum node_stat_item idx, int val)
> + enum node_stat_item idx, long val)
> {
> struct mem_cgroup *memcg = pn->memcg;
> int i = memcg_stats_index(idx);
> --
> 2.20.1
>