Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753144AbdLNOyw (ORCPT ); Thu, 14 Dec 2017 09:54:52 -0500 Received: from mail-wr0-f195.google.com ([209.85.128.195]:35172 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753029AbdLNOyr (ORCPT ); Thu, 14 Dec 2017 09:54:47 -0500 X-Google-Smtp-Source: ACJfBotk7EjcCI+gfWikxDrWruZhm+tfpjj1xfmCTt9DguDLLCrnpfQXn3h+USZW3ZiPN8sL8wJ4WQ== Date: Thu, 14 Dec 2017 14:54:43 +0000 From: Edward Napierala To: Michal Hocko Cc: Andrew Morton , linux-api@vger.kernel.org, Khalid Aziz , Michael Ellerman , Russell King - ARM Linux , Andrea Arcangeli , linux-mm@kvack.org, LKML , linux-arch@vger.kernel.org, Florian Weimer , John Hubbard , Matthew Wilcox , Abdul Haleem , Joel Stanley , Kees Cook , jasone@google.com, davidtgoldblatt@gmail.com Subject: Re: [PATCH v2 0/2] mm: introduce MAP_FIXED_SAFE Message-ID: <20171214145443.GA2202@brick> References: <20171213092550.2774-1-mhocko@kernel.org> <20171213163210.6a16ccf8753b74a6982ef5b6@linux-foundation.org> <20171214131526.GM16951@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171214131526.GM16951@dhcp22.suse.cz> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1363 Lines: 25 On 1214T1415, Michal Hocko wrote: > On Thu 14-12-17 12:44:17, Edward Napierala wrote: > > Regarding the name - how about adopting MAP_EXCL? It was introduced in > > FreeBSD, > > and seems to do exactly this; quoting mmap(2): > > > > MAP_FIXED Do not permit the system to select a different address > > than the one specified. If the specified address > > cannot be used, mmap() will fail. If MAP_FIXED is > > specified, addr must be a multiple of the page size. > > If MAP_EXCL is not specified, a successful MAP_FIXED > > request replaces any previous mappings for the > > process' pages in the range from addr to addr + len. > > In contrast, if MAP_EXCL is specified, the request > > will fail if a mapping already exists within the > > range. > > I am not familiar with the FreeBSD implementation but from the above it > looks like MAP_EXCL is a MAP_FIXED mofifier which is not how we are > going to implement it in linux due to reasons mentioned in this cover > letter. Using the same name would be more confusing than helpful I am > afraid. Sorry, missed that. Indeed, reusing a name with a different semantics would be a bad idea.