From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758703AbZFCPHt (ORCPT ); Wed, 3 Jun 2009 11:07:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758955AbZFCPH2 (ORCPT ); Wed, 3 Jun 2009 11:07:28 -0400 Received: from mx2.redhat.com ([66.187.237.31]:56802 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758951AbZFCPH0 (ORCPT ); Wed, 3 Jun 2009 11:07:26 -0400 Date: Wed, 3 Jun 2009 16:47:23 +0200 From: Andrea Arcangeli To: akpm@linux-foundation.org Cc: hugh@veritas.com, linux-kernel@vger.kernel.org, Izik Eidus , nickpiggin@yahoo.com.au, chrisw@redhat.com, linux-mm@kvack.org, riel@redhat.com Subject: [PATCH] ksm: fix losing visibility of part of rmap_item->next list Message-ID: <20090603144723.GC30426@random.random> References: <20090603144552.GB30426@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090603144552.GB30426@random.random> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrea Arcangeli The tree_item->rmap_item is the head of the list and as such it must not be overwritten except in the case that the element we removed (rmap_item) was the previous head of the list, in which case it would also have rmap_item->prev set to null. Signed-off-by: Andrea Arcangeli --- diff --git a/mm/ksm.c b/mm/ksm.c index 74d921b..6d8dfee 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -397,10 +397,10 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) free_tree_item(tree_item); nnodes_stable_tree--; } else if (!rmap_item->prev) { + BUG_ON(tree_item->rmap_item != rmap_item); tree_item->rmap_item = rmap_item->next; - } else { - tree_item->rmap_item = rmap_item->prev; - } + } else + BUG_ON(tree_item->rmap_item == rmap_item); } else { /* * We dont rb_erase(&tree_item->node) here, beacuse