Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752413Ab0BRSDE (ORCPT ); Thu, 18 Feb 2010 13:03:04 -0500 Received: from gir.skynet.ie ([193.1.99.77]:44658 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750993Ab0BRSCp (ORCPT ); Thu, 18 Feb 2010 13:02:45 -0500 From: Mel Gorman To: Andrea Arcangeli Cc: Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , KOSAKI Motohiro , Rik van Riel , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 02/12] mm,migration: Do not try to migrate unmapped anonymous pages Date: Thu, 18 Feb 2010 18:02:32 +0000 Message-Id: <1266516162-14154-3-git-send-email-mel@csn.ul.ie> X-Mailer: git-send-email 1.6.5 In-Reply-To: <1266516162-14154-1-git-send-email-mel@csn.ul.ie> References: <1266516162-14154-1-git-send-email-mel@csn.ul.ie> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1421 Lines: 40 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 --- mm/migrate.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 63addfa..1ce6a2f 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -606,6 +606,16 @@ 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/