Re: 2.6.22-rc4-mm1

Andrew Morton
2007-06-07T15:35:38Z

On Thu, 7 Jun 2007 21:47:06 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> Question.
>
> While writing memory unplug, I noticed this code.
> ==
> static int
> fixup_anon_page(pte_t *pte, unsigned long start, unsigned long end, void *priv)
> {
> struct vm_area_struct *vma = priv;
> struct page *page = vm_normal_page(vma, start, *pte);
>
> if (page && PageAnon(page))
> page->index = linear_page_index(vma, start);
>
> return 0;
> }
>
> static int fixup_anon_pages(struct vm_area_struct *vma)
> {
> struct mm_walk walk = {
> .pte_entry = fixup_anon_page,
> };
>
> return walk_page_range(vma->vm_mm,
> vma->vm_start, vma->vm_end, &walk, vma);
> }

I assume the above is your code - it's not in the tree?

>
> I think that 'pte' passed to fixup_anon_page() by walk_page_range()
> is not guaranteed to be 'Present'.

yup - the pagewalker only checks for !pte_none().

> Then, vm_normal_page() will show print_bad_pte().

> If this never occur now, I'll add my own check code for memory migration by kernel here.

Yes, you'll need to perform additional filtering where appropriate.

> (Sorry, I can't find who should be CCed.)

Matt and David did most of the work here.