Re: mapcount corruption regression

[Yi Zhang]

Hi Dan
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index dfd82f51ba66..7ed99314dcdf 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -829,6 +829,7 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)
>          }
>
>          free_page((unsigned long)pmd_sv);
> +       pgtable_pmd_page_dtor(virt_to_page(pmd));
>          free_page((unsigned long)pmd);
>
>          return 1;
>
> In 2013 Kirill noticed that he missed a pmd page table free site:
>
>      c283610e44ec x86, mm: do not leak page->ptl for pmd page tables
>
> In 2018 Toshi added a new pmd page table free site without the destructor:
>
>      28ee90fe6048 x86/mm: implement free pmd/pte page interfaces
>
> In 2020 Willy adds PG_table accounting that flags the missing
> pgtable_pmd_page_dtor()
>
> Yi, I would appreciate a confirmation that the fix works for you.
I applied the patch to v5.10-rc3 ~ v5.10-rc6, and cannot reproduce this 
issue with my regression test now, feel free to add:
Tested-by: Yi Zhang <yi.zhang@xxxxxxxxxx>


Thanks
Yi