Re: [PATCH 3/7] mm/hugetlb: Add page_mask for hugetlb_follow_page_mask()

[David Hildenbrand]

On 19.06.23 23:43, Peter Xu wrote:
> On Tue, Jun 13, 2023 at 05:53:42PM -0400, Peter Xu wrote:
> > @@ -6506,6 +6507,7 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
> >   		 * because we hold the ptl lock and have verified pte_present().
> >   		 */
> >   		WARN_ON_ONCE(try_grab_page(page, flags));
> > +		*page_mask = huge_page_mask(h);
>
> Sorry, I was wrong this line.  It should be:
>
> 		*page_mask = ~huge_page_mask(h) >> PAGE_SHIFT;

That's ... surprising. It feels like either page_mask or 
huge_page_mask() has a misleading name ....

h->mask = ~(huge_page_size(h) - 1);


For PMDs, we do

ctx->page_mask = HPAGE_PMD_NR - 1;


Maybe

*page_mask = PHYS_PFN(huge_page_size(h)) - 1;

Would be clearer.

I guess "page_mask" should actually be "pfn_mask" ... but the meaning 
regarding PAGE_MASK are still inverted ...

--
Cheers,

David / dhildenb