From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751272AbaFZSXK (ORCPT ); Thu, 26 Jun 2014 14:23:10 -0400 Received: from mga09.intel.com ([134.134.136.24]:9282 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750862AbaFZSXI (ORCPT ); Thu, 26 Jun 2014 14:23:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,554,1400050800"; d="scan'208";a="564021718" From: Andi Kleen To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, tony.luck@intel.com, linux-kernel@vger.kernel.org, Andi Kleen , Naoya Horiguchi , dave.hansen@linux.intel.com Subject: [PATCH] hwpoison: Fix race with changing page during offlining Date: Thu, 26 Jun 2014 11:22:52 -0700 Message-Id: <1403806972-14267-1-git-send-email-andi@firstfloor.org> X-Mailer: git-send-email 1.9.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andi Kleen While running the mcelog test suite on 3.14 I hit the following VM_BUG_ON: soft_offline: 0x56d4: unknown non LRU page type 3ffff800008000 page:ffffea000015b400 count:3 mapcount:2097169 mapping: (null) index:0xffff8800056d7000 page flags: 0x3ffff800004081(locked|slab|head) ------------[ cut here ]------------ kernel BUG at mm/rmap.c:1495! I think what happened is that a LRU page turned into a slab page in parallel with offlining. memory_failure initially tests for this case, but doesn't retest later after the page has been locked. This patch fixes this race. It also check for the case that the page changed compound pages. Unfortunately since it's a race I wasn't able to reproduce later, so the specific case is not tested. Cc: Naoya Horiguchi Cc: dave.hansen@linux.intel.com Signed-off-by: Andi Kleen --- mm/memory-failure.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 90002ea..e277726a 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1143,6 +1143,22 @@ int memory_failure(unsigned long pfn, int trapno, int flags) lock_page(hpage); /* + * The page could have turned into a non LRU page or + * changed compound pages during the locking. + * If this happens just bail out. + */ + if (compound_head(p) != hpage) { + action_result(pfn, "different compound page after locking", IGNORED); + res = -EBUSY; + goto out; + } + if (!PageLRU(hpage)) { + action_result(pfn, "non LRU after locking", IGNORED); + res = -EBUSY; + goto out; + } + + /* * We use page flags to determine what action should be taken, but * the flags can be modified by the error containment action. One * example is an mlocked page, where PG_mlocked is cleared by -- 1.9.3