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

Fan Ni
2025-05-04T21:35:26Z

On Wed, Apr 30, 2025 at 09:58:35AM +0200, Oscar Salvador wrote:
> 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...

Hi Oscar,

Thanks for the feedback.
Since the sugguested change here is minor and does not affect the
function, and we do not have a aligned opinion here.
https://lore.kernel.org/linux-mm/b23ef51b-1284-4168-8157-432c3e045788@redhat.com/
I will leave it as it is until there are more pushes for the change.

>
> > 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.

Will update in the next version. Thanks.

Fan

>
>
>
> --
> Oscar Salvador
> SUSE Labs
>

--
Fan Ni