Re: [PATCH 09/16] debug_vm_pgtable/set_pud: Don't use set_pud_at to update an existing pud entry

[Anshuman Khandual]

On 08/12/2020 12:03 PM, Aneesh Kumar K.V wrote:
> set_pud_at() should not be used to set a pte entry at locations that
> already holds a valid pte entry. Architectures like ppc64 don't do TLB
> invalidate in set_pud_at() and hence expect it to be used to set locations
> that are not a valid PTE.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
> ---
>  mm/debug_vm_pgtable.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 60bf876081b8..644d28861ce9 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -278,9 +278,6 @@ static void __init pud_advanced_tests(struct mm_struct 
> *mm,
>       WARN_ON(pud_write(pud));
>  
>  #ifndef __PAGETABLE_PMD_FOLDED
> -
> -     pud = pud_mkhuge(pfn_pud(pfn, prot));
> -     set_pud_at(mm, vaddr, pudp, pud);
>       pudp_huge_get_and_clear(mm, vaddr, pudp);
>       pud = READ_ONCE(*pudp);
>       WARN_ON(!pud_none(pud));
> @@ -302,6 +299,11 @@ static void __init pud_advanced_tests(struct mm_struct 
> *mm,
>       pud = READ_ONCE(*pudp);
>       WARN_ON(!(pud_write(pud) && pud_dirty(pud)));
>  
> +     pudp_huge_get_and_clear_full(vma, vaddr, pudp, 1);
> +     pud = READ_ONCE(*pudp);
> +     WARN_ON(!pud_none(pud));
> +
> +     pud = pud_mkhuge(pfn_pud(pfn, prot));
>       pud = pud_mkyoung(pud);
>       set_pud_at(mm, vaddr, pudp, pud);
>       pudp_test_and_clear_young(vma, vaddr, pudp);

Very similar to [PATCH 3/16] wrt set_pte_at(), please fold it.