Re: [PATCH v4 07/12] mm/swapfile: Add batched version of folio_dup_swap

["David Hildenbrand (Arm)" <david@kernel.org>]

On 5/26/26 08:36, Dev Jain wrote:
> Add folio_dup_swap_pages to handle a batch of consecutive pages. Note
> that folio_dup_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_dup_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_dup_swap() if it
> wants to operate on the entire folio.
> 
> Signed-off-by: Dev Jain <dev.jain@arm.com>
> ---
>  mm/rmap.c     |  2 +-
>  mm/shmem.c    |  2 +-
>  mm/swap.h     | 19 +++++++++++++++++--
>  mm/swapfile.c | 14 ++++++--------
>  4 files changed, 25 insertions(+), 12 deletions(-)
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index ead031361bc61..3065d384cadf8 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -2331,7 +2331,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>  				goto finish_unmap;
>  			}
>  
> -			if (folio_dup_swap(folio, subpage) < 0) {
> +			if (folio_dup_swap_pages(folio, subpage, 1) < 0) {
>  				set_pte_at(mm, address, pvmw.pte, pteval);
>  				goto walk_abort;
>  			}
> diff --git a/mm/shmem.c b/mm/shmem.c
> index bab3529af23c5..5e4f521399847 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1698,7 +1698,7 @@ int shmem_writeout(struct folio *folio, struct swap_iocb **plug,
>  			spin_unlock(&shmem_swaplist_lock);
>  		}
>  
> -		folio_dup_swap(folio, NULL);
> +		folio_dup_swap(folio);
>  		shmem_delete_from_page_cache(folio, swp_to_radix_entry(folio->swap));
>  
>  		BUG_ON(folio_mapped(folio));
> diff --git a/mm/swap.h b/mm/swap.h
> index b57547c25ffc9..36c69b2788c77 100644
> --- a/mm/swap.h
> +++ b/mm/swap.h
> @@ -206,7 +206,8 @@ extern int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp);
>   * folio_put_swap(): does the opposite thing of folio_dup_swap().
>   */
>  int folio_alloc_swap(struct folio *folio);
> -int folio_dup_swap(struct folio *folio, struct page *page);
> +int folio_dup_swap_pages(struct folio *folio, struct page *page,
> +			 unsigned long nr_pages);

Nit: \tab\tab

-- 
Cheers,

David