From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx147.postini.com [74.125.245.147]) by kanga.kvack.org (Postfix) with SMTP id EECD26B005D for ; Tue, 21 Aug 2012 11:20:23 -0400 (EDT) Message-ID: <1345562411.23018.111.camel@twins> Subject: Re: [PATCH v8 1/5] mm: introduce a common interface for balloon pages mobility From: Peter Zijlstra Date: Tue, 21 Aug 2012 17:20:11 +0200 In-Reply-To: References: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Rafael Aquini Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel , Mel Gorman , Andi Kleen , Andrew Morton , Konrad Rzeszutek Wilk , Minchan Kim , paulmck On Tue, 2012-08-21 at 09:47 -0300, Rafael Aquini wrote: > + mapping =3D rcu_access_pointer(page->mapping); > + if (mapping) > + mapping =3D mapping->assoc_mapping;=20 The comment near rcu_access_pointer() explicitly says: * Return the value of the specified RCU-protected pointer, but omit the * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful * when the value of this pointer is accessed, but the pointer is not * dereferenced, Yet you dereference the pointer... smells like fail to me. -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754848Ab2HUPUd (ORCPT ); Tue, 21 Aug 2012 11:20:33 -0400 Received: from merlin.infradead.org ([205.233.59.134]:51472 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751521Ab2HUPU2 convert rfc822-to-8bit (ORCPT ); Tue, 21 Aug 2012 11:20:28 -0400 Message-ID: <1345562411.23018.111.camel@twins> Subject: Re: [PATCH v8 1/5] mm: introduce a common interface for balloon pages mobility From: Peter Zijlstra To: Rafael Aquini Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel , Mel Gorman , Andi Kleen , Andrew Morton , Konrad Rzeszutek Wilk , Minchan Kim , paulmck Date: Tue, 21 Aug 2012 17:20:11 +0200 In-Reply-To: References: Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-08-21 at 09:47 -0300, Rafael Aquini wrote: > + mapping = rcu_access_pointer(page->mapping); > + if (mapping) > + mapping = mapping->assoc_mapping; The comment near rcu_access_pointer() explicitly says: * Return the value of the specified RCU-protected pointer, but omit the * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful * when the value of this pointer is accessed, but the pointer is not * dereferenced, Yet you dereference the pointer... smells like fail to me.