From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx128.postini.com [74.125.245.128]) by kanga.kvack.org (Postfix) with SMTP id 5897C6B0074 for ; Tue, 21 Aug 2012 11:16:25 -0400 (EDT) Message-ID: <1345562166.23018.109.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 17:16:06 +0200 In-Reply-To: <20120821135223.GA7117@redhat.com> References: <20120821135223.GA7117@redhat.com> 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: "Michael S. Tsirkin" Cc: Rafael Aquini , linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , Rik van Riel , Mel Gorman , Andi Kleen , Andrew Morton , Konrad Rzeszutek Wilk , Minchan Kim On Tue, 2012-08-21 at 16:52 +0300, Michael S. Tsirkin wrote: > > + rcu_read_lock(); > > + mapping =3D rcu_dereference(page->mapping); > > + if (mapping_balloon(mapping)) > > + ret =3D true; > > + rcu_read_unlock(); >=20 > This looks suspicious: you drop rcu_read_unlock > so can't page switch from balloon to non balloon?=20 RCU read lock is a non-exclusive lock, it cannot avoid anything like that. -- 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