Re: [PATCH 17/19 v2] parisc/mm/fault.c: Port OOM changes to do_page_fault

[Kautuk Consul <consul.kautuk@xxxxxxxxx>]

Hi,

Can you please review this patch ?

Many archs have actually accepted this change so I think maybe this is okay. :)

Thanks,
Kautuk.

On Sat, Mar 31, 2012 at 5:36 PM, Kautuk Consul <consul.kautuk@xxxxxxxxx> wrote:
> Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
> (mm: retry page fault when blocking on disk transfer) and
> commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
> (x86,mm: make pagefault killable)
>
> The above commits introduced changes into the x86 pagefault handler
> for making the page fault handler retryable as well as killable.
>
> These changes reduce the mmap_sem hold time, which is crucial
> during OOM killer invocation.
>
> Signed-off-by: Kautuk Consul <consul.kautuk@xxxxxxxxx>
> ---
>  arch/parisc/mm/fault.c |   29 ++++++++++++++++++++++++-----
>  1 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
> index 18162ce..bd66ed6 100644
> --- a/arch/parisc/mm/fault.c
> +++ b/arch/parisc/mm/fault.c
> @@ -175,10 +175,12 @@ void do_page_fault(struct pt_regs *regs, unsigned long code,
>        struct mm_struct *mm = tsk->mm;
>        unsigned long acc_type;
>        int fault;
> +       unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
>
>        if (in_atomic() || !mm)
>                goto no_context;
>
> +retry:
>        down_read(&mm->mmap_sem);
>        vma = find_vma_prev(mm, address, &prev_vma);
>        if (!vma || address < vma->vm_start)
> @@ -201,7 +203,12 @@ good_area:
>         * fault.
>         */
>
> -       fault = handle_mm_fault(mm, vma, address, (acc_type & VM_WRITE) ? FAULT_FLAG_WRITE : 0);
> +       fault = handle_mm_fault(mm, vma, address,
> +                       flags | ((acc_type & VM_WRITE) ? FAULT_FLAG_WRITE : 0));
> +
> +       if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
> +               return;
> +
>        if (unlikely(fault & VM_FAULT_ERROR)) {
>                /*
>                 * We hit a shared mapping outside of the file, or some
> @@ -214,10 +221,22 @@ good_area:
>                        goto bad_area;
>                BUG();
>        }
> -       if (fault & VM_FAULT_MAJOR)
> -               current->maj_flt++;
> -       else
> -               current->min_flt++;
> +       if (flags & FAULT_FLAG_ALLOW_RETRY) {
> +               if (fault & VM_FAULT_MAJOR)
> +                       current->maj_flt++;
> +               else
> +                       current->min_flt++;
> +               if (fault & VM_FAULT_RETRY) {
> +                       flags &= ~FAULT_FLAG_ALLOW_RETRY;
> +
> +                        /* No need to up_read(&mm->mmap_sem) as we would
> +                        * have already released it in __lock_page_or_retry
> +                        * in mm/filemap.c.
> +                        */
> +
> +                       goto retry;
> +               }
> +       }
>        up_read(&mm->mmap_sem);
>        return;
>
> --
> 1.7.5.4
>
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