From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753287AbYEORTs (ORCPT ); Thu, 15 May 2008 13:19:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751153AbYEORTk (ORCPT ); Thu, 15 May 2008 13:19:40 -0400 Received: from hellhawk.shadowen.org ([80.68.90.175]:3222 "EHLO hellhawk.shadowen.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbYEORTj (ORCPT ); Thu, 15 May 2008 13:19:39 -0400 From: Andy Whitcroft To: linux-mm@kvack.org Cc: Andrew Morton , Christoph Lameter , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Rik van Riel , Jeremy Fitzhardinge , linux-kernel@vger.kernel.org Subject: [PATCH 0/3] explicitly document overloaded page flags Message-ID: Date: Thu, 15 May 2008 18:19:38 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the recent page flag reorganisation we have a single enum which defines the valid page flags and their values, nice and clear. However there are a number of bits which are overloaded by different subsystems. Firstly there is PG_owner_priv_1 which is used by filesystems and by XEN. Secondly both SLOB and SLUB use a couple of extra page bits to manage internal state for pages they own; both overlay other bits. All of these "aliases" are scattered about the source making it very hard for a reader to know if the bits are safe to rely on in all contexts; confusion here is bad. As we now have a single place where the bits are clearly assigned it makes sense to clarify the reuse of bits by making the aliases explicit and visible with the original bit assignments. This patch creates explicit aliases within the enum itself for the overloaded bits and uses those aliases throughout. Andrew please consider for -mm. -apw