From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758419Ab0CLQle (ORCPT ); Fri, 12 Mar 2010 11:41:34 -0500 Received: from gir.skynet.ie ([193.1.99.77]:40205 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756987Ab0CLQl3 (ORCPT ); Fri, 12 Mar 2010 11:41:29 -0500 From: Mel Gorman To: Andrew Morton Cc: Andrea Arcangeli , 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 02/11] mm,migration: Do not try to migrate unmapped anonymous pages Date: Fri, 12 Mar 2010 16:41:18 +0000 Message-Id: <1268412087-13536-3-git-send-email-mel@csn.ul.ie> X-Mailer: git-send-email 1.6.5 In-Reply-To: <1268412087-13536-1-git-send-email-mel@csn.ul.ie> References: <1268412087-13536-1-git-send-email-mel@csn.ul.ie> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Acked-by: Rik van Riel --- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 30FB66B0152 for ; Fri, 12 Mar 2010 11:42:12 -0500 (EST) From: Mel Gorman Subject: [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages Date: Fri, 12 Mar 2010 16:41:18 +0000 Message-Id: <1268412087-13536-3-git-send-email-mel@csn.ul.ie> In-Reply-To: <1268412087-13536-1-git-send-email-mel@csn.ul.ie> References: <1268412087-13536-1-git-send-email-mel@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Andrea Arcangeli , 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 Acked-by: Rik van Riel --- 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, 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