From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031102Ab2ERDGb (ORCPT ); Thu, 17 May 2012 23:06:31 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:40463 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762559Ab2ERCwd (ORCPT ); Thu, 17 May 2012 22:52:33 -0400 Message-Id: <20120518023255.315413519@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Fri, 18 May 2012 03:33:01 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Chris Metcalf , Mel Gorman , Hillf Danton , Hugh Dickins , Michal Hocko , KAMEZAWA Hiroyuki Subject: [ 07/53] hugetlb: prevent BUG_ON in hugetlb_fault() -> hugetlb_cow() In-Reply-To: <20120518023254.339945758@decadent.org.uk> X-SA-Exim-Connect-IP: 192.168.4.185 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Metcalf commit 4998a6c0edce7fae9c0a5463f6ec3fa585258ee7 upstream. Commit 66aebce747eaf ("hugetlb: fix race condition in hugetlb_fault()") added code to avoid a race condition by elevating the page refcount in hugetlb_fault() while calling hugetlb_cow(). However, one code path in hugetlb_cow() includes an assertion that the page count is 1, whereas it may now also have the value 2 in this path. The consensus is that this BUG_ON has served its purpose, so rather than extending it to cover both cases, we just remove it. Signed-off-by: Chris Metcalf Acked-by: Mel Gorman Acked-by: Hillf Danton Acked-by: Hugh Dickins Cc: Michal Hocko Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- mm/hugetlb.c | 1 - 1 file changed, 1 deletion(-) --- linux.orig/mm/hugetlb.c +++ linux/mm/hugetlb.c @@ -2405,7 +2405,6 @@ if (outside_reserve) { BUG_ON(huge_pte_none(pte)); if (unmap_ref_private(mm, vma, old_page, address)) { - BUG_ON(page_count(old_page) != 1); BUG_ON(huge_pte_none(pte)); spin_lock(&mm->page_table_lock); goto retry_avoidcopy;