[PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages
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From: Mel Gorman on 12 Mar 2010 11:50 rmap_walk_anon() was triggering errors in memory compaction that looks like use-after-free errors in anon_vma. The problem appears to be that between the page being isolated from the LRU and rcu_read_lock() being taken, the mapcount of the page dropped to 0 and the anon_vma was freed. This patch skips the migration of anon pages that are not mapped by anyone. Signed-off-by: Mel Gorman <mel(a)csn.ul.ie> Acked-by: Rik van Riel <riel(a)redhat.com> --- mm/migrate.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 98eaaf2..3c491e3 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -602,6 +602,16 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, * just care Anon page here. */ if (PageAnon(page)) { + /* + * 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)) + goto uncharge; + rcu_read_lock(); rcu_locked = 1; anon_vma = page_anon_vma(page); -- 1.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |