Re: [PATCH v8 2/3] mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios

[Yosry Ahmed]

On Thu, Sep 5, 2024 at 5:11 PM Barry Song <21cnbao@xxxxxxxxx> wrote:
>
> From: Barry Song <v-songbaohua@xxxxxxxx>
>
> With large folios swap-in, we might need to uncharge multiple entries all
> together, add nr argument in mem_cgroup_swapin_uncharge_swap().
>
> For the existing two users, just pass nr=1.
>
> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>

Reviewed-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>

> Acked-by: Chris Li <chrisl@xxxxxxxxxx>
> Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Gao Xiang <xiang@xxxxxxxxxx>
> Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Kairui Song <kasong@xxxxxxxxxxx>
> Cc: Kairui Song <ryncsn@xxxxxxxxx>
> Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Nhat Pham <nphamcs@xxxxxxxxx>
> Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
> Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
> Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Cc: Yang Shi <shy828301@xxxxxxxxx>
> Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> ---
>  include/linux/memcontrol.h | 5 +++--
>  mm/memcontrol.c            | 7 ++++---
>  mm/memory.c                | 2 +-
>  mm/swap_state.c            | 2 +-
>  4 files changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 2ef94c74847d..34d2da05f2f1 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -699,7 +699,8 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
>
>  int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
>                                   gfp_t gfp, swp_entry_t entry);
> -void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry);
> +
> +void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
>
>  void __mem_cgroup_uncharge(struct folio *folio);
>
> @@ -1206,7 +1207,7 @@ static inline int mem_cgroup_swapin_charge_folio(struct folio *folio,
>         return 0;
>  }
>
> -static inline void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
> +static inline void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry, unsigned int nr)
>  {
>  }
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index bda6f75d22ff..c0d36ca20332 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4559,14 +4559,15 @@ int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
>
>  /*
>   * mem_cgroup_swapin_uncharge_swap - uncharge swap slot
> - * @entry: swap entry for which the page is charged
> + * @entry: the first swap entry for which the pages are charged
> + * @nr_pages: number of pages which will be uncharged
>   *
>   * Call this function after successfully adding the charged page to swapcache.
>   *
>   * Note: This function assumes the page for which swap slot is being uncharged
>   * is order 0 page.
>   */
> -void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
> +void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
>  {
>         /*
>          * Cgroup1's unified memory+swap counter has been charged with the
> @@ -4586,7 +4587,7 @@ void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
>                  * let's not wait for it.  The page already received a
>                  * memory+swap charge, drop the swap entry duplicate.
>                  */
> -               mem_cgroup_uncharge_swap(entry, 1);
> +               mem_cgroup_uncharge_swap(entry, nr_pages);
>         }
>  }
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 42674c0748cb..cdf03b39a92c 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4100,7 +4100,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>                                         ret = VM_FAULT_OOM;
>                                         goto out_page;
>                                 }
> -                               mem_cgroup_swapin_uncharge_swap(entry);
> +                               mem_cgroup_swapin_uncharge_swap(entry, 1);
>
>                                 shadow = get_shadow_from_swap_cache(entry);
>                                 if (shadow)
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index a042720554a7..4669f29cf555 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -522,7 +522,7 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
>         if (add_to_swap_cache(new_folio, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
>                 goto fail_unlock;
>
> -       mem_cgroup_swapin_uncharge_swap(entry);
> +       mem_cgroup_swapin_uncharge_swap(entry, 1);
>
>         if (shadow)
>                 workingset_refault(new_folio, shadow);
> --
> 2.34.1
>