Re: [PATCH v4 08/12] mm/swapfile: Add batched version of folio_put_swap

[David Hildenbrand (Arm)]

On 5/26/26 08:36, Dev Jain wrote:
> Add folio_put_swap_pages to handle a batch of consecutive pages. Note
> that folio_put_swap already can handle a subset of this: nr_pages == 1 and
> nr_pages == folio_nr_pages(folio). Generalize this to any nr_pages.
> 
> Currently we have a not-so-nice logic of passing in subpage == NULL if
> we mean to exercise the logic on the entire folio, and subpage != NULL if
> we want to exercise the logic on only that subpage. Remove this
> indirection: the caller invokes folio_put_swap_pages() if it wants to
> operate on a range of pages in the folio (i.e nr_pages may be anything
> between 1 till folio_nr_pages()), and invokes folio_put_swap() if it

"between 1 and folio_nr_pages()" ?

> wants to operate on the entire folio.
> 
> Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
> ---


[...]

> +++ b/mm/swap.h
> @@ -208,7 +208,8 @@ extern int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp);
>  int folio_alloc_swap(struct folio *folio);
>  int folio_dup_swap_pages(struct folio *folio, struct page *page,
>  			 unsigned long nr_pages);
> -void folio_put_swap(struct folio *folio, struct page *page);
> +void folio_put_swap_pages(struct folio *folio, struct page *page,
> +			  unsigned long nr_pages);

Nit \tab\tab (same below)

>  
>  /* For internal use */
>  extern void __swap_cluster_free_entries(struct swap_info_struct *si,
> @@ -397,7 +398,8 @@ static inline int folio_dup_swap_pages(struct folio *folio, struct page *page,
>  	return -EINVAL;
>  }
>  


[...]

>  
>  	swap_put_entries_cluster(si, swp_offset(entry), nr_pages, false);
>  }
> @@ -2499,7 +2497,8 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
>  		new_pte = pte_mkuffd_wp(new_pte);
>  setpte:
>  	set_pte_at(vma->vm_mm, addr, pte, new_pte);
> -	folio_put_swap(swapcache, folio_file_page(swapcache, swp_offset(entry)));
> +	folio_put_swap_pages(swapcache,
> +			     folio_file_page(swapcache, swp_offset(entry)), 1);
>  out:
>  	if (pte)
>  		pte_unmap_unlock(pte, ptl);


We could consider having a simple folio_put_swap_page() helper. But maybe most
of these will be converted to batching in the long run either way.

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David