Re: [PATCH 2/4] Add replace_page(), change the mapping of pte from one page into another

Christoph Lameter
2008-11-12T20:28:26Z

On Wed, 12 Nov 2008, Andrea Arcangeli wrote:

> On Tue, Nov 11, 2008 at 09:10:45PM -0600, Christoph Lameter wrote:
> > get_user_pages() cannot get to it since the pagetables have already been
> > modified. If get_user_pages runs then the fault handling will occur
> > which will block the thread until migration is complete.
>
> migrate.c does nothing for ptes pointing to swap entries and
> do_swap_page won't wait for them either. Assume follow_page in

If a anonymous page is a swap page then it has a mapping.
migrate_page_move_mapping() will lock the radix tree and ensure that no
additional reference (like done by do_swap_page) is established during
migration.

> However it's not exactly the same bug as the one in fork, I was
> talking about before, it's also not o_direct specific. Still

So far I have seen wild ideas not bugs.