Re: [PATCH 2/3] mm: Simplify split_page_memcg()

[Zi Yan <ziy@nvidia.com>]

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On 4 Nov 2024, at 16:05, Matthew Wilcox (Oracle) wrote:

> The last argument to split_page_memcg() is now always 0, so remove it,
> effectively reverting commit b8791381d7ed.

You forgot to cc me about this.

>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  include/linux/memcontrol.h |  4 ++--
>  mm/memcontrol.c            | 26 ++++++++++++++------------
>  mm/page_alloc.c            |  4 ++--
>  3 files changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 5502aa8e138e..a787080f814f 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1044,7 +1044,7 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm,
>  	rcu_read_unlock();
>  }
>
> -void split_page_memcg(struct page *head, int old_order, int new_order);
> +void split_page_memcg(struct page *first, int order);
>
>  #else /* CONFIG_MEMCG */
>
> @@ -1463,7 +1463,7 @@ void count_memcg_event_mm(struct mm_struct *mm, enum vm_event_item idx)
>  {
>  }
>
> -static inline void split_page_memcg(struct page *head, int old_order, int new_order)
> +static inline void split_page_memcg(struct page *first, int order)
>  {
>  }
>  #endif /* CONFIG_MEMCG */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5e44d6e7591e..506439a5dcfe 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3034,25 +3034,27 @@ void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
>  }
>
>  /*
> - * Because folio_memcg(head) is not set on tails, set it now.
> + * The memcg data is only set on the first page, now transfer it to all the
> + * other pages.
>   */
> -void split_page_memcg(struct page *head, int old_order, int new_order)
> +void split_page_memcg(struct page *first, int order)

So split_page_memcg() only handles kmem pages, it is better to rename it
to split_kmem_page_memcg() to avoid confusion. Especially if this patchset
is merged before my folio_split() patchset and I did not notice it, my
patchset would cause memcg issues, since I was still using split_page_memcg()
during folio split.


--
Best Regards,
Yan, Zi

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