On Mon, 10 May 2010, Mel Gorman wrote:

> > A simple way to disallow migration of pages is to increment the refcount
> > of a page.
> I guess it could be done by walking the page-tables in advance of the move
> and elevating the page count of any pages faulted and then finding those
> pages afterwards.  The fail path would be a bit of a pain though if the page
> tables are partially moved though. It's unnecessarily complicated when the
> temporary stack can be easily avoided.

Faulting during exec? Dont we hold mmap_sem for write? A get_user_pages()
or so on the range will increment the refcount.