Re: [PATCH 3/6] mm/page_io: use swap entries directly in zeromap helpers

[Lorenzo Stoakes (ARM)]

On Thu, Aug 06, 2026 at 06:55:35PM -0400, Tal Zussman wrote:
> Increment swp_entry_t::val directly instead of recomputing each entry
> with page_swap_entry(). This removes the last struct page usage in
> page_io.c and saves one call to compound_head() per page.
>
> Signed-off-by: Tal Zussman <tz2294@xxxxxxxxxxxx>

Lord I just looked at page_swap_entry() and... yeah. This is an improvement
thanks :)

I haven't looked at the rest of the series so maybe you already did it but I
wonder if we could remove it altogether?

Should we rename page_io.c to folio_io.c now? :P

Anyway LGTM so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>

> ---
>  mm/page_io.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/mm/page_io.c b/mm/page_io.c
> index 43b4383a4729..c6d0949b3f1e 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -159,7 +159,7 @@ static void swap_zeromap_folio_set(struct folio *folio)
>  	struct obj_cgroup *objcg = get_obj_cgroup_from_folio(folio);
>  	int nr_pages = folio_nr_pages(folio);
>  	struct swap_cluster_info *ci;
> -	swp_entry_t entry;
> +	swp_entry_t entry = folio->swap;
>  	unsigned int i;
>
>  	VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
> @@ -167,8 +167,8 @@ static void swap_zeromap_folio_set(struct folio *folio)
>
>  	ci = swap_cluster_get_and_lock(folio);
>  	for (i = 0; i < folio_nr_pages(folio); i++) {
> -		entry = page_swap_entry(folio_page(folio, i));
>  		__swap_table_set_zero(ci, swp_cluster_offset(entry));
> +		entry.val++;
>  	}
>  	swap_cluster_unlock(ci);
>
> @@ -182,7 +182,7 @@ static void swap_zeromap_folio_set(struct folio *folio)
>  static void swap_zeromap_folio_clear(struct folio *folio)
>  {
>  	struct swap_cluster_info *ci;
> -	swp_entry_t entry;
> +	swp_entry_t entry = folio->swap;
>  	unsigned int i;
>
>  	VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
> @@ -190,8 +190,8 @@ static void swap_zeromap_folio_clear(struct folio *folio)
>
>  	ci = swap_cluster_get_and_lock(folio);
>  	for (i = 0; i < folio_nr_pages(folio); i++) {
> -		entry = page_swap_entry(folio_page(folio, i));
>  		__swap_table_clear_zero(ci, swp_cluster_offset(entry));
> +		entry.val++;
>  	}
>  	swap_cluster_unlock(ci);
>  }
>
> --
> 2.39.5
>

--
Cheers, Lorenzo