On Wed, 15 Sep 2010, Andrea Arcangeli wrote:
> From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
>
> The below bug in fork lead to the rmap walk finding the parent huge-pmd twice
> instead of just one, because the anon_vma_chain objects of the child vma still
> point to the vma->vm_mm of the parent. The below patch fixes it by making the
> rmap walk accurate during fork. It's not a big deal normally but it
> worth being accurate considering the cost is the same.
>
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
> ---
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -360,10 +360,10 @@ static int dup_mmap(struct mm_struct *mm
> if (IS_ERR(pol))
> goto fail_nomem_policy;
> vma_set_policy(tmp, pol);
> + tmp->vm_mm = mm;
> if (anon_vma_fork(tmp, mpnt))
> goto fail_nomem_anon_vma_fork;
> tmp->vm_flags &= ~VM_LOCKED;
> - tmp->vm_mm = mm;
> tmp->vm_next = tmp->vm_prev = NULL;
> file = tmp->vm_file;
> if (file) {
--
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