From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752235AbXCZLu6 (ORCPT ); Mon, 26 Mar 2007 07:50:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752234AbXCZLu6 (ORCPT ); Mon, 26 Mar 2007 07:50:58 -0400 Received: from smtp.osdl.org ([65.172.181.24]:54787 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752140AbXCZLu5 (ORCPT ); Mon, 26 Mar 2007 07:50:57 -0400 Date: Mon, 26 Mar 2007 03:50:27 -0800 From: Andrew Morton To: David Howells Cc: bryan.wu@analog.com, Pekka Enberg , linux-kernel@vger.kernel.org, Hugh Dickins Subject: Re: [PATCH -mm] Revoke core code: fix nommu arch compiling error bug Message-Id: <20070326035027.c522cdf5.akpm@linux-foundation.org> In-Reply-To: <6017.1174908318@redhat.com> References: <20070326024143.a226c9b2.akpm@linux-foundation.org> <1174904637.32691.86.camel@roc-desktop> <6017.1174908318@redhat.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 26 Mar 2007 12:25:18 +0100 David Howells wrote: > Andrew Morton wrote: > > > Offending patch is > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc4/2.6.21-rc4-mm1/broken-out/nommu-hide-vm_mm-in-nommu-mode.patch, > > which seems rather dumb. Or at least, its changelog does a good job of > > making it look dumb. > > vm_mm is always NULL under NOMMU as it currently stands. As far as I know, > this has been true since the NOMMU mm stuff was first included (I'm not sure > the VMAs of the first NOMMU mm code *had* a vm_mm). Hugh (I think it was) > suggested that since this was always NULL, then it should be excised from the > struct in NOMMU-mode. > > The reason is that, at the moment, VMAs are a global *shared* resource in > NOMMU-mode. Each process has a list of global VMAs that it subscribes to, but > that's it. This (a) slightly reduces the amount of metadata allocated > (possibly), and (b) makes sharing of executables and libraries much easier. whoa. You live and learn. Logical, I guess. I agree that in that case, we just don't want vm_mm to exist in NOMMU builds - it's better to fail at compile time. I'll touch up the changelog for nommu-hide-vm_mm-in-nommu-mode.patch and then I'll temporarily drop it so the blackfin guys can test their work, I guess.