From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933006AbXCZABB (ORCPT ); Sun, 25 Mar 2007 20:01:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933045AbXCZABA (ORCPT ); Sun, 25 Mar 2007 20:01:00 -0400 Received: from smtp.osdl.org ([65.172.181.24]:36478 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933006AbXCZAA7 (ORCPT ); Sun, 25 Mar 2007 20:00:59 -0400 Date: Sun, 25 Mar 2007 16:00:50 -0800 From: Andrew Morton To: Miklos Szeredi Cc: a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch 2/3] only allow nonlinear vmas for ram backed filesystems Message-Id: <20070325160050.fe7cb284.akpm@linux-foundation.org> In-Reply-To: References: 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 Sat, 24 Mar 2007 23:09:19 +0100 Miklos Szeredi wrote: > Dirty page accounting/limiting doesn't work for nonlinear mappings, Doesn't it? iirc the problem is that we don't correctly re-clean the ptes while starting writeout. And the dirty-page accounting is in fact correct (it'd darn well better be). > so > for non-ram backed filesystems emulate with linear mappings. This > retains ABI compatibility with previous kernels at minimal code cost. > > All known users of nonlinear mappings actually use tmpfs, so this > shouldn't have any negative effect. Unless someone is using remap_file_pages() against an ext3 file, in which case their application stops working? That would be a problem. These guys: http://www.technovelty.org/code/linux/fremap.html, for example, will be in for a little surprise.