On Thu, Aug 28, 2025 at 12:01:22AM +0200, David Hildenbrand wrote:
> nth_page() is no longer required when iterating over pages within a
> single folio, so let's just drop it when recording subpages.
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
This looks correct to me, so notwithtsanding suggestion below, LGTM and:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> ---
> mm/gup.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index b2a78f0291273..89ca0813791ab 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -488,12 +488,11 @@ static int record_subpages(struct page *page, unsigned long sz,
> unsigned long addr, unsigned long end,
> struct page **pages)
> {
> - struct page *start_page;
> int nr;
>
> - start_page = nth_page(page, (addr & (sz - 1)) >> PAGE_SHIFT);
> + page += (addr & (sz - 1)) >> PAGE_SHIFT;
> for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
> - pages[nr] = nth_page(start_page, nr);
> + pages[nr] = page++;
This is really nice, but I wonder if (while we're here) we can't be even
more clear as to what's going on here, e.g.:
static int record_subpages(struct page *page, unsigned long sz,
unsigned long addr, unsigned long end,
struct page **pages)
{
size_t offset_in_folio = (addr & (sz - 1)) >> PAGE_SHIFT;
struct page *subpage = page + offset_in_folio;
for (; addr != end; addr += PAGE_SIZE)
*pages++ = subpage++;
return nr;
}
Or some variant of that with the masking stuff self-documented.
>
> return nr;
> }
> @@ -1512,7 +1511,7 @@ static long __get_user_pages(struct mm_struct *mm,
> }
>
> for (j = 0; j < page_increm; j++) {
> - subpage = nth_page(page, j);
> + subpage = page + j;
> pages[i + j] = subpage;
> flush_anon_page(vma, subpage, start + j * PAGE_SIZE);
> flush_dcache_page(subpage);
> --
> 2.50.1
>
Cheers, Lorenzo
