Re: [PATCH v3 3/3] mm: memcontrol: correct the nr_pages parameter type of mem_cgroup_update_lru_size()

[Lorenzo Stoakes (Oracle)]

On Fri, Mar 27, 2026 at 06:16:30PM +0800, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
>
> The nr_pages parameter of mem_cgroup_update_lru_size() represents a page
> count. During the reparenting of LRU folios, the value passed to it can
> potentially exceed the maximum value of a 32-bit integer. It should be
> declared as long instead of int to match the types used in lruvec size
> accounting and to prevent possible overflow.
>
> Update the parameter type to long to ensure correctness.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>

LGTM so:

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx>

> ---
>  include/linux/memcontrol.h | 2 +-
>  mm/memcontrol.c            | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 0782c72a1997b..4a7d8c4f55b48 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -874,7 +874,7 @@ static inline bool mem_cgroup_online(struct mem_cgroup *memcg)
>  }
>
>  void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
> -		int zid, int nr_pages);
> +		int zid, long nr_pages);
>
>  static inline
>  unsigned long mem_cgroup_get_zone_lru_size(struct lruvec *lruvec,
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 51d72ddf08119..bf74167d77c5b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1472,7 +1472,7 @@ struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
>   * to or just after a page is removed from an lru list.
>   */
>  void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
> -				int zid, int nr_pages)
> +				int zid, long nr_pages)
>  {
>  	struct mem_cgroup_per_node *mz;
>  	unsigned long *lru_size;
> @@ -1489,7 +1489,7 @@ void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
>
>  	size = *lru_size;
>  	if (WARN_ONCE(size < 0,
> -		"%s(%p, %d, %d): lru_size %ld\n",
> +		"%s(%p, %d, %ld): lru_size %ld\n",
>  		__func__, lruvec, lru, nr_pages, size)) {
>  		VM_BUG_ON(1);
>  		*lru_size = 0;
> --
> 2.20.1
>