On Wed, Apr 12, 2017 at 03:04:57PM +0100, Punit Agrawal wrote:
> When memory failure is enabled, a poisoned hugepage pte is marked as a
> swap entry. huge_pte_offset() does not return the poisoned page table
> entries when it encounters PUD/PMD hugepages.
>
> This behaviour of huge_pte_offset() leads to error such as below when
> munmap is called on poisoned hugepages.
>
> [ 344.165544] mm/pgtable-generic.c:33: bad pmd 000000083af00074.
>
> Fix huge_pte_offset() to return the poisoned pte which is then
> appropriately handled by the generic layer code.
>
> Signed-off-by: Punit Agrawal <punit.agra...@arm.com>
> Cc: Catalin Marinas <catalin.mari...@arm.com>
> Cc: Steve Capper <steve.cap...@arm.com>
> Cc: David Woods <dwo...@mellanox.com>
> ---
> arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 7514a000e361..5f1832165d69 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -143,15 +143,24 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned
> long 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))
> - return NULL;
>
> - if (pud_huge(*pud))
> + pud = pud_offset(pgd, addr);
> + /*
> + * In case of HW Poisoning, a hugepage pud/pmd can contain
> + * poisoned entries. Poisoned entries are marked as swap
> + * entries.
> + *
> + * For puds/pmds that are not present, check to see if it
> + * could be a swap entry (!present and !none).
> + */
> + if ((!pte_present(pud_pte(*pud)) && !pud_none(*pud)) || pud_huge(*pud))
> return (pte_t *)pud;
Since we use puds as huge pages, can we just change pud_present() to
match the pmd_present()? I'd like to see similar checks for pud and pmd,
it would be easier to follow. Something like (unchecked):
if (pud_none(*pud))
return NULL;
/* swap or huge page */
if (!pud_present(*pud) || pud_huge(*pud))
return (pte_t *)pud;
/* table; check the next level */
> +
> pmd = pmd_offset(pud, addr);
> - if (!pmd_present(*pmd))
> + if (pmd_none(*pmd))
> return NULL;
> + if (!pmd_present(*pmd) && !pmd_none(*pmd))
> + return (pte_t *)pmd;
At this point, we already know that pmd_none(*pmd) is false, no ned to
check it again.
--
Catalin
