On Fri, Nov 04, 2016 at 09:48:14AM -0600, Catalin Marinas wrote: > On Fri, Nov 04, 2016 at 10:52:17AM +0800, Huang Shijie wrote: > > On Thu, Nov 03, 2016 at 06:16:16PM -0600, Catalin Marinas wrote: > > > On Thu, Nov 03, 2016 at 10:27:38AM +0800, Huang Shijie wrote: > > > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > > > > index 2e49bd2..4811ef1 100644 > > > > --- a/arch/arm64/mm/hugetlbpage.c > > > > +++ b/arch/arm64/mm/hugetlbpage.c > > > > @@ -61,10 +61,6 @@ static int find_num_contig(struct mm_struct *mm, > > > > unsigned long addr, > > > > return 1; > > > > } > > > > pmd = pmd_offset(pud, addr); > > > > - if (!pmd_present(*pmd)) { > > > > - VM_BUG_ON(!pmd_present(*pmd)); > > > > - return 1; > > > > - } > > > > if ((pte_t *)pmd == ptep) { > > > > *pgsize = PMD_SIZE; > > > > return CONT_PMDS; > > > > > > BTW, for the !pud_present() and !pgd_present() cases, shouldn't > > > find_num_contig() actually return 0? These are more likely real bugs, so > > > no point in setting the huge pte. > > > > The kernel will not call the find_num_contig() if the PGD/PUD are empty. > > Please see the code in the hugetlb_fault(). > > > > ------------------------------------------------------ > > ptep = huge_pte_offset(mm, address); > > if (ptep) { > > ............................... > > } else { > > ptep = huge_pte_alloc(mm, address, huge_page_size(h)); > > if (!ptep) > > return VM_FAULT_OOM; > > } > > ------------------------------------------------------ > > Exactly. So what is the reason for returning 1 if !pgd_present()? Would I think the author was too cautious for returning 1 if !pgd_present(). :) > removing the checks entirely or adding BUG() be a better option? I will remove the checks in the next version.
Thanks Huang Shijie