Re: [PATCH 6/7] mm/gup: Accelerate thp gup even for "pages != NULL"

[Matthew Wilcox]

On Tue, Jun 13, 2023 at 05:53:45PM -0400, Peter Xu wrote:
> +			if (page_increm > 1)
> +				WARN_ON_ONCE(
> +				    try_grab_folio(compound_head(page),

You don't need to call compound_head() here; try_grab_folio() works
on tail pages just fine.

> +						   page_increm - 1,
> +						   foll_flags) == NULL);
> +
> +			for (j = 0; j < page_increm; j++) {
> +				subpage = nth_page(page, j);
> +				pages[i+j] = subpage;
> +				flush_anon_page(vma, subpage, start + j * PAGE_SIZE);
> +				flush_dcache_page(subpage);

You're better off calling flush_dcache_folio() right at the end.