Re: [PATCH v3 3/4] mm/hugetlb: Refactor __unmap_hugepage_range() to take folio instead of page

Oscar Salvador
2025-04-30T07:58:42Z

On Mon, Apr 28, 2025 at 10:11:46AM -0700, nifan.cxl@gmail.com wrote:
> From: Fan Ni <fan.ni@samsung.com>
>
> The function __unmap_hugepage_range() has two kinds of users:
> 1) unmap_hugepage_range(), which passes in the head page of a folio.
> Since unmap_hugepage_range() already takes folio and there are no other
> uses of the folio struct in the function, it is natural for
> __unmap_hugepage_range() to take folio also.
> 2) All other uses, which pass in NULL pointer.
>
> In both cases, we can pass in folio. Refactor __unmap_hugepage_range() to
> take folio.
>
> Signed-off-by: Fan Ni <fan.ni@samsung.com>

Reviewed-by: Oscar Salvador <osalvador@suse.de>

But:

> void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
> unsigned long start, unsigned long end,
> - struct page *ref_page, zap_flags_t zap_flags)
> + struct folio *folio, zap_flags_t zap_flags)

I think we are kinda losing information here. ref_ was a good hint
and...

> struct mm_struct *mm = vma->vm_mm;
> unsigned long address;
> @@ -5885,8 +5885,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
> * page is being unmapped, not a range. Ensure the page we
> * are about to unmap is the actual page of interest.
> */
> - if (ref_page) {
> - if (page != ref_page) {
> + if (folio) {
> + if (page_folio(page) != folio) {

You have to update the comment above, since we are not passing a
reference page anymore but a folio.

--
Oscar Salvador
SUSE Labs