| Date | Tue, 23 Mar 2010 12:22:57 -0500 (CDT) | From | Christoph Lameter <> | Subject | Re: [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages |
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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;
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