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

[Lorenzo Stoakes (Oracle)]

On Tue, Mar 24, 2026 at 07:31:29PM +0800, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
>
> The nr_pages parameter of mem_cgroup_update_lru_size() should clearly
> be long instead of int, let's correct it.

Hmm, but are you ever going to be adding that many pages? I guess technically
correct though.

You should list all the callers and how they use long or unsigned long,
e.g. update_lru_sizes(), lruvec_reparent_lru(), lru_gen_reparent_memcg().

And maybe look a bit into why this was int, if there's any reason for it at
all :)

I'm assuming there's no weird 'let's intentionally let this overflow'
behaviour here.

>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>

This one looks correct overall, so, with commit message improved:

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

> ---
>  include/linux/memcontrol.h | 2 +-
>  mm/memcontrol.c            | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 0861589695298..dc3fa687759b4 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -878,7 +878,7 @@ 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 4a78550f6174e..6491ca74b3398 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1466,7 +1466,7 @@ 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;
> --
> 2.20.1
>