Re: [PATCH v1 19/36] io_uring/zcrx: remove nth_page() usage within folio

On Thu, Aug 28, 2025 at 12:01:23AM +0200, David Hildenbrand wrote:
> Within a folio/compound page, nth_page() is no longer required.
> Given that we call folio_test_partial_kmap()+kmap_local_page(), the code
> would already be problematic if the pages would span multiple folios.
>
> So let's just assume that all src pages belong to a single
> folio/compound page and can be iterated ordinarily. The dst page is
> currently always a single page, so we're not actually iterating
> anything.
>
> Reviewed-by: Pavel Begunkov <[email protected]>
> Cc: Jens Axboe <[email protected]>
> Cc: Pavel Begunkov <[email protected]>
> Signed-off-by: David Hildenbrand <[email protected]>

On basis of src pages being within the same folio, LGTM, so:

Reviewed-by: Lorenzo Stoakes <[email protected]>

> ---
>  io_uring/zcrx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
> index e5ff49f3425e0..18c12f4b56b6c 100644
> --- a/io_uring/zcrx.c
> +++ b/io_uring/zcrx.c
> @@ -975,9 +975,9 @@ static ssize_t io_copy_page(struct io_copy_cache *cc, struct page *src_page,
>
>  		if (folio_test_partial_kmap(page_folio(dst_page)) ||
>  		    folio_test_partial_kmap(page_folio(src_page))) {
> -			dst_page = nth_page(dst_page, dst_offset / PAGE_SIZE);
> +			dst_page += dst_offset / PAGE_SIZE;
>  			dst_offset = offset_in_page(dst_offset);
> -			src_page = nth_page(src_page, src_offset / PAGE_SIZE);
> +			src_page += src_offset / PAGE_SIZE;
>  			src_offset = offset_in_page(src_offset);
>  			n = min(PAGE_SIZE - src_offset, PAGE_SIZE - dst_offset);
>  			n = min(n, len);
> --
> 2.50.1
>