From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63C5DC46475 for ; Tue, 23 Oct 2018 17:01:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1906720665 for ; Tue, 23 Oct 2018 17:01:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1906720665 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728662AbeJXBZw (ORCPT ); Tue, 23 Oct 2018 21:25:52 -0400 Received: from mx2.suse.de ([195.135.220.15]:44674 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727758AbeJXBZw (ORCPT ); Tue, 23 Oct 2018 21:25:52 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 34C92AF8E; Tue, 23 Oct 2018 17:01:39 +0000 (UTC) Date: Tue, 23 Oct 2018 19:01:36 +0200 From: Michal Hocko To: Dan Williams Cc: Andrew Morton , =?iso-8859-1?B?Suly9G1l?= Glisse , Christoph Hellwig , Linux MM , Linux Kernel Mailing List Subject: Re: [PATCH v7 1/7] mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL Message-ID: <20181023170136.GV18839@dhcp22.suse.cz> References: <153936657159.1198040.4489957977352276272.stgit@dwillia2-desk3.amr.corp.intel.com> <153936657702.1198040.119388737535638846.stgit@dwillia2-desk3.amr.corp.intel.com> <20181017081753.GG18839@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 17-10-18 09:30:58, Dan Williams wrote: > On Wed, Oct 17, 2018 at 1:18 AM Michal Hocko wrote: [...] > > > Again, devm_memremap_pagex() exposes and relies upon core kernel > > > internal assumptions and will continue to evolve along with 'struct > > > page', memory hotplug, and support for new memory types / topologies. > > > Only an in-kernel GPL-only driver is expected to keep up with this > > > ongoing evolution. This interface, and functionality derived from this > > > interface, is not suitable for kernel-external drivers. > > > > I do not follow this line of argumentation though. We generally do not > > care about out-of-tree modules and breaking them if the interface has to > > be updated. > > Exactly right. The EXPORT_SYMBOL_GPL is there to say that this api has > deep enough ties into the core kernel to lower the confidence that the > API will stay stable from one kernel revision to the next. It's also > an api that is attracting widening and varied reuse and the long term > health of the implementation depends on being able to peer deeply into > its users and refactor the interface and the core kernel as a result. I am sorry I do not follow. For in-tree modules you have to update users whether the export is GPL or not and we do not care _at all_ about out of tree because we do not guarantee _any_ kABI/API stability (Documentation/process/stable-api-nonsense.rst). Anyway, I do not really care much, but I find the way of the argumentation dubious. I can clearly understand a simple line "me as the author want this GPL - live with that". -- Michal Hocko SUSE Labs