On Tue, Mar 23, 2010 at 12:22:57PM -0500, Christoph Lameter wrote:
> On Tue, 23 Mar 2010, Mel Gorman wrote:
>
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index 98eaaf2..6eb1efe 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -603,6 +603,19 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
> > */
> > if (PageAnon(page)) {
> > rcu_read_lock();
> > +
> > + /*
> > + * If the page has no mappings any more, just bail. An
> > + * unmapped anon page is likely to be freed soon but worse,
> > + * it's possible its anon_vma disappeared between when
> > + * the page was isolated and when we reached here while
> > + * the RCU lock was not held
> > + */
> > + if (!page_mapcount(page)) {
> > + rcu_read_unlock();
> > + goto uncharge;
> > + }
> > +
> > rcu_locked = 1;
> > anon_vma = page_anon_vma(page);
> > atomic_inc(&anon_vma->migrate_refcount);
>
> A way to make this simpler would be to move "rcu_locked = 1" before the
> if statement and then do
>
> if (!page_mapcount(page))
> goto rcu_unlock;
>
True. Fixed.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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