On Thu, Jun 08, 2017 at 01:59:46PM +0100, Mark Rutland wrote: > On Thu, Jun 08, 2017 at 11:35:48AM +0000, Ard Biesheuvel wrote: > > @@ -287,10 +288,10 @@ struct page *vmalloc_to_page(const void *vmalloc_addr) > > if (p4d_none(*p4d)) > > return NULL; > > pud = pud_offset(p4d, addr); > > - if (pud_none(*pud)) > > + if (pud_none(*pud) || WARN_ON_ONCE(pud_huge(*pud))) > > return NULL; > > pmd = pmd_offset(pud, addr); > > - if (pmd_none(*pmd)) > > + if (pmd_none(*pmd) || WARN_ON_ONCE(pmd_huge(*pmd))) > > return NULL; > > I think it might be better to use p*d_bad() here, since that doesn't > depend on CONFIG_HUGETLB_PAGE. > > While the cross-arch semantics are a little fuzzy, my understanding is > those should return true if an entry is not a pointer to a next level of > table (so pXd_huge(p) implies pXd_bad(p)). Ugh; it turns out this isn't universally true. I see that at least arch/hexagon's pmd_bad() always returns 0, and they support CONFIG_HUGETLB_PAGE. So I guess there isn't an arch-neutral, always-available way of checking this. Sorry for having mislead you. For arm64, p*d_bad() would still be preferable, so maybe we should check both? Thanks, Mark. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
