From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422754AbXDXRiq (ORCPT ); Tue, 24 Apr 2007 13:38:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422838AbXDXRiq (ORCPT ); Tue, 24 Apr 2007 13:38:46 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:36895 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1422754AbXDXRip (ORCPT ); Tue, 24 Apr 2007 13:38:45 -0400 Date: Tue, 24 Apr 2007 10:38:44 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Hugh Dickins cc: Andrew Morton , Nick Piggin , linux-kernel@vger.kernel.org, pj@sgi.com Subject: Re: Pagecache: find_or_create_page does not call a proper page allocator function In-Reply-To: Message-ID: References: <20070423142919.5809e03f.akpm@linux-foundation.org> <20070423154224.15ebf8f7.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 24 Apr 2007, Hugh Dickins wrote: > I've not yet looked at the patch under discussion, but this remark > prompts me... a couple of days ago I got very worried by the various > hard-wired GFP_HIGHUSER allocations in mm/migrate.c and mm/mempolicy.c, > and wondered how those would work out if someone has a blockdev mmap'ed. Hmmm.... These not that critical given that 32 bit NUMA systems are a bit rare. And if a page is in the wrong area then it can be bounced before I/O is performed on it. > (If vma->vm_file is non-NULL, we can be sure vma->vm_file->f_mapping > is non-NULL, can't we? Some common code assumes that, some does not: > I've avoided cargo-cult safety below, but don't let me make it unsafe.) > > > Is there a problem with page migration to HIGHMEM, if pages were > mapped from a GFP_USER block device? I failed to demonstrate any > problem, but here's a quick fix if needed. If a page is migrated into a different zone and then a write attempt is made on it then the page will be bounced into a zone from which the device can write from.