Re: [PATCH 02/14] mm: fix major/minor fault accounting on retried fault

[Ying Han <yinghan@google.com>]

On Tue, Apr 7, 2009 at 12:17 AM, Wu Fengguang <fengguang.wu@intel.com> wrote:
> VM_FAULT_RETRY does make major/minor faults accounting a bit twisted..
>
> Cc: Ying Han <yinghan@google.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
>  arch/x86/mm/fault.c |    2 ++
>  mm/memory.c         |   22 ++++++++++++++--------
>  2 files changed, 16 insertions(+), 8 deletions(-)
>
> --- mm.orig/arch/x86/mm/fault.c
> +++ mm/arch/x86/mm/fault.c
> @@ -1160,6 +1160,8 @@ good_area:
>        if (fault & VM_FAULT_RETRY) {
>                if (retry_flag) {
>                        retry_flag = 0;
> +                       tsk->maj_flt++;
> +                       tsk->min_flt--;
>                        goto retry;
>                }
>                BUG();
sorry, little bit confuse here. are we assuming the retry path will
return min_flt as always?


> --- mm.orig/mm/memory.c
> +++ mm/mm/memory.c
> @@ -2882,26 +2882,32 @@ int handle_mm_fault(struct mm_struct *mm
>        pud_t *pud;
>        pmd_t *pmd;
>        pte_t *pte;
> +       int ret;
>
>        __set_current_state(TASK_RUNNING);
>
> -       count_vm_event(PGFAULT);
> -
> -       if (unlikely(is_vm_hugetlb_page(vma)))
> -               return hugetlb_fault(mm, vma, address, write_access);
> +       if (unlikely(is_vm_hugetlb_page(vma))) {
> +               ret = hugetlb_fault(mm, vma, address, write_access);
> +               goto out;
> +       }
>
> +       ret = VM_FAULT_OOM;
>        pgd = pgd_offset(mm, address);
>        pud = pud_alloc(mm, pgd, address);
>        if (!pud)
> -               return VM_FAULT_OOM;
> +               goto out;
>        pmd = pmd_alloc(mm, pud, address);
>        if (!pmd)
> -               return VM_FAULT_OOM;
> +               goto out;
>        pte = pte_alloc_map(mm, pmd, address);
>        if (!pte)
> -               return VM_FAULT_OOM;
> +               goto out;
>
> -       return handle_pte_fault(mm, vma, address, pte, pmd, write_access);
> +       ret = handle_pte_fault(mm, vma, address, pte, pmd, write_access);
> +out:
> +       if (!(ret & VM_FAULT_RETRY))
> +               count_vm_event(PGFAULT);
> +       return ret;
>  }
>
>  #ifndef __PAGETABLE_PUD_FOLDED
>
> --
>
>