Will Deacon <will.dea...@arm.com> writes:
> On Wed, Jun 07, 2017 at 03:30:37PM +0100, Catalin Marinas wrote:
>> On Wed, Jun 07, 2017 at 02:47:32PM +0100, Will Deacon wrote:
>> > On Wed, May 17, 2017 at 04:23:34PM +0100, Punit Agrawal wrote:
>> > > --- a/arch/arm64/mm/hugetlbpage.c
>> > > +++ b/arch/arm64/mm/hugetlbpage.c
>> > > @@ -136,36 +136,27 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
>> > > unsigned long addr)
>> > > {
>> > > pgd_t *pgd;
>> > > pud_t *pud;
>> > > - pmd_t *pmd = NULL;
>> > > - pte_t *pte = NULL;
>> > > + pmd_t *pmd;
>> > >
>> > > pgd = pgd_offset(mm, addr);
>> > > pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
>> > > if (!pgd_present(*pgd))
>> > > return NULL;
>> > > +
>> > > pud = pud_offset(pgd, addr);
>> > > - if (!pud_present(*pud))
>> > > + if (pud_none(*pud))
>> > > return NULL;
>> >
>> > Do you actually need this special case?
>> >
>> > > -
>> > > - if (pud_huge(*pud))
>> > > + /* swap or huge page */
>> > > + if (!pud_present(*pud) || pud_huge(*pud))
>> >
>> > ... couldn't you just add a '|| pud_none(*pud)' in here?
>> >
I think an earlier version took this approach but...
>> > > return (pte_t *)pud;
>>
>> But then you no longer return NULL if *pud == 0.
>
> Does that actually matter? The bits of hugetlb code I looked at will
> deferenced the returned pud and handle the huge_pte_none case correctly.
For hugetlb fault handling (hugetlb_fault()), returning NULL vs pointer
to the pud/pmd results in different behaviour. If we return the pud when
pud_none(), then we lose the resulting hugepage size check we get from
huge_pte_alloc().
>
> Will
