From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id CF1E06B0099 for ; Thu, 18 Feb 2010 13:03:26 -0500 (EST) From: Mel Gorman 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> 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: owner-linux-mm@kvack.org 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org