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

David Laight
2026-03-26T14:37:44Z

On Thu, 26 Mar 2026 09:19:29 +0000
"Lorenzo Stoakes (Oracle)" <ljs@kernel.org> wrote:

> 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.

Won't that are be true on 32bit systems?
Which means the underlying values need to be u64 not long.

David

> >
> > 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
> >
>