Re: [PATCH 05/13] mm: Make use of the anon_vma ref count

Christian Ehrhardt
2010-04-09T07:04:16Z

Hi,

On Thu, Apr 08, 2010 at 09:17:42PM +0200, Peter Zijlstra wrote:
> @@ -302,23 +307,33 @@ again:
> goto out;
>
> anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
> - spin_lock(&anon_vma->lock);
> + if (!atomic_inc_not_zero(&anon_vma->ref))
> + anon_vma = NULL;
>
> if (page_rmapping(page) != anon_vma) {
> - spin_unlock(&anon_vma->lock);
> + anon_vma_put(anon_vma);
> goto again;
> }

AFAICS anon_vma_put might be called with anon_vma == NULL here which
will oops on the ref count. Not sure if

page_rmapping(page) == anon_vma == NULL

is possible, too.

regards Christian