Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754133AbdLDK5M (ORCPT ); Mon, 4 Dec 2017 05:57:12 -0500 Received: from mx2.suse.de ([195.135.220.15]:50658 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754108AbdLDK5F (ORCPT ); Mon, 4 Dec 2017 05:57:05 -0500 Date: Mon, 4 Dec 2017 11:55:49 +0100 From: Cyril Hrubis To: john.hubbard@gmail.com Cc: Michael Kerrisk , linux-man , linux-api@vger.kernel.org, Michael Ellerman , linux-mm@kvack.org, LKML , linux-arch@vger.kernel.org, Jann Horn , Matthew Wilcox , Michal Hocko , John Hubbard Subject: Re: [PATCH v2] mmap.2: MAP_FIXED updated documentation Message-ID: <20171204105549.GA31332@rei> References: <20171204021411.4786-1-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171204021411.4786-1-jhubbard@nvidia.com> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 709 Lines: 19 Hi! I know that we are not touching the rest of the existing description for MAP_FIXED however the second sentence in the manual page says that "addr must be a multiple of the page size." Which however is misleading as this is not enough on some architectures. Code in the wild seems to (mis)use SHMLBA for aligment purposes but I'm not sure that we should advise something like that in the manpages. So what about something as: "addr must be suitably aligned, for most architectures multiple of page size is sufficient, however some may impose additional restrictions for page mapping addresses." Which should at least hint the reader that this is architecture specific. -- Cyril Hrubis chrubis@suse.cz