On Wed, Nov 11, 2020 at 03:30:22PM +0000, Matthew Wilcox wrote:
> This confuses me. Why only special-case hugetlbfs pages here? Should
> they really be treated differently from THP? If you want to consider
> that we might be mapping a page that's twice as big as a PUD entry and
> this is only half of it, then the simple way is:
>
> if (pud_leaf(pud)) {
> #ifdef pud_page
> page = compound_head(pud_page(*pud));
> return page_size(page);
Also; this is 'wrong'. The purpose of this function is to return the
hardware TLB size of a given address. The above will return the compound
size, for any random compound page, which would be myrads of reasons.
So the PageHuge() thing tells us it is a HugeTLB page and those are
(barring hardware TLB promotion/demotion) guaranteed to reflect the
actual TLB size.
> #else
> return 1ULL << PUD_SHIFT;
> #endif
> }
