From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752584Ab0IFIMd (ORCPT ); Mon, 6 Sep 2010 04:12:33 -0400 Received: from smtp-out.google.com ([216.239.44.51]:52305 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752450Ab0IFIM2 (ORCPT ); Mon, 6 Sep 2010 04:12:28 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id: references:user-agent:mime-version:content-type:x-system-of-record; b=JcsMP/bQAvRw6PMQuQlAkZ52e1QeDSR0+zD49IT5XW/FrifNXaAEIY7AI74oshA+a weWdaP0MeKGgquTh1+c1g== Date: Mon, 6 Sep 2010 01:12:38 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@sister.anvils To: Andrew Morton cc: KAMEZAWA Hiroyuki , KOSAKI Motohiro , "Rafael J. Wysocki" , Ondrej Zary , Andrea Gelmini , Balbir Singh , Andrea Arcangeli , Nigel Cunningham , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/4] swap: prevent reuse during hibernation In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (LSU 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Move the hibernation check from scan_swap_map() into try_to_free_swap(): to catch not only the common case when hibernation's allocation itself triggers swap reuse, but also the less likely case when concurrent page reclaim (shrink_page_list) might happen to try_to_free_swap from a page. Hibernation already clears __GFP_IO from the gfp_allowed_mask, to stop reclaim from going to swap: check that to prevent swap reuse too. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro Cc: "Rafael J. Wysocki" Cc: Ondrej Zary Cc: Andrea Gelmini Cc: Balbir Singh Cc: Andrea Arcangeli Cc: Nigel Cunningham Cc: stable@kernel.org --- mm/swapfile.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) --- swap1/mm/swapfile.c 2010-09-05 22:37:07.000000000 -0700 +++ swap2/mm/swapfile.c 2010-09-05 22:45:54.000000000 -0700 @@ -318,10 +318,8 @@ checks: if (offset > si->highest_bit) scan_base = offset = si->lowest_bit; - /* reuse swap entry of cache-only swap if not hibernation. */ - if (vm_swap_full() - && usage == SWAP_HAS_CACHE - && si->swap_map[offset] == SWAP_HAS_CACHE) { + /* reuse swap entry of cache-only swap if not busy. */ + if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { int swap_was_freed; spin_unlock(&swap_lock); swap_was_freed = __try_to_reclaim_swap(si, offset); @@ -688,6 +686,24 @@ int try_to_free_swap(struct page *page) if (page_swapcount(page)) return 0; + /* + * Once hibernation has begun to create its image of memory, + * there's a danger that one of the calls to try_to_free_swap() + * - most probably a call from __try_to_reclaim_swap() while + * hibernation is allocating its own swap pages for the image, + * but conceivably even a call from memory reclaim - will free + * the swap from a page which has already been recorded in the + * image as a clean swapcache page, and then reuse its swap for + * another page of the image. On waking from hibernation, the + * original page might be freed under memory pressure, then + * later read back in from swap, now with the wrong data. + * + * Hibernation clears bits from gfp_allowed_mask to prevent + * memory reclaim from writing to disk, so check that here. + */ + if (!(gfp_allowed_mask & __GFP_IO)) + return 0; + delete_from_swap_cache(page); SetPageDirty(page); return 1;