From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 15 May 2008 10:26:25 -0700 (PDT) From: Christoph Lameter Subject: Re: [PATCH 0/3] explicitly document overloaded page flags In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andy Whitcroft Cc: linux-mm@kvack.org, Andrew Morton , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Rik van Riel , Jeremy Fitzhardinge , linux-kernel@vger.kernel.org List-ID: On Thu, 15 May 2008, Andy Whitcroft wrote: > 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. Ahh. Great! I considered doing that work too but never got around to it. -- 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