Re: [PATCH] mm: Simplify calling a compound page destructor

[David Hildenbrand <david@redhat.com>]

On 17.05.20 12:50, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> None of the three callers of get_compound_page_dtor() want to know
> the value; they just want to call the function.  Replace it with
> destroy_compound_page() which calls the dtor for them.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  include/linux/mm.h | 4 ++--
>  mm/swap.c          | 5 +----
>  mm/vmscan.c        | 4 ++--
>  3 files changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 31ec312e8903..688558c57751 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -865,10 +865,10 @@ static inline void set_compound_page_dtor(struct page *page,
>  	page[1].compound_dtor = compound_dtor;
>  }
>  
> -static inline compound_page_dtor *get_compound_page_dtor(struct page *page)
> +static inline void destroy_compound_page(struct page *page)
>  {
>  	VM_BUG_ON_PAGE(page[1].compound_dtor >= NR_COMPOUND_DTORS, page);
> -	return compound_page_dtors[page[1].compound_dtor];
> +	compound_page_dtors[page[1].compound_dtor](page);
>  }
>  
>  static inline unsigned int compound_order(struct page *page)
> diff --git a/mm/swap.c b/mm/swap.c
> index a37bd7b202ac..416fb89c86c1 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -83,8 +83,6 @@ static void __put_single_page(struct page *page)
>  
>  static void __put_compound_page(struct page *page)
>  {
> -	compound_page_dtor *dtor;
> -
>  	/*
>  	 * __page_cache_release() is supposed to be called for thp, not for
>  	 * hugetlb. This is because hugetlb page does never have PageLRU set
> @@ -93,8 +91,7 @@ static void __put_compound_page(struct page *page)
>  	 */
>  	if (!PageHuge(page))
>  		__page_cache_release(page);
> -	dtor = get_compound_page_dtor(page);
> -	(*dtor)(page);
> +	destroy_compound_page(page);
>  }
>  
>  void __put_page(struct page *page)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index cc555903a332..d96e18726751 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1442,7 +1442,7 @@ static unsigned int shrink_page_list(struct list_head *page_list,
>  		 * appear not as the counts should be low
>  		 */
>  		if (unlikely(PageTransHuge(page)))
> -			(*get_compound_page_dtor(page))(page);
> +			destroy_compound_page(page);
>  		else
>  			list_add(&page->lru, &free_pages);
>  		continue;
> @@ -1870,7 +1870,7 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
>  
>  			if (unlikely(PageCompound(page))) {
>  				spin_unlock_irq(&pgdat->lru_lock);
> -				(*get_compound_page_dtor(page))(page);
> +				destroy_compound_page(page);
>  				spin_lock_irq(&pgdat->lru_lock);
>  			} else
>  				list_add(&page->lru, &pages_to_free);
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb