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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 7BD52C433DF for ; Sun, 19 Jul 2020 17:55:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61E6F21744 for ; Sun, 19 Jul 2020 17:55:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726073AbgGSRzN (ORCPT ); Sun, 19 Jul 2020 13:55:13 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:38660 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725783AbgGSRzN (ORCPT ); Sun, 19 Jul 2020 13:55:13 -0400 Received: from ip5f5af08c.dynamic.kabel-deutschland.de ([95.90.240.140] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jxDWl-0001P4-0X; Sun, 19 Jul 2020 17:55:07 +0000 Date: Sun, 19 Jul 2020 19:55:06 +0200 From: Christian Brauner To: Al Viro Cc: David Howells , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Michael Kerrisk Subject: Re: [PATCH 0/4] fs: add mount_setattr() Message-ID: <20200719175506.fwxsb6r6pfrdhvxb@wittgenstein> References: <20200714161415.3886463-1-christian.brauner@ubuntu.com> <20200719171054.GK2786714@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200719171054.GK2786714@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Sun, Jul 19, 2020 at 06:10:54PM +0100, Al Viro wrote: > On Tue, Jul 14, 2020 at 06:14:11PM +0200, Christian Brauner wrote: > > > mount_setattr() can be expected to grow over time and is designed with > > extensibility in mind. It follows the extensible syscall pattern we have > > used with other syscalls such as openat2(), clone3(), > > sched_{set,get}attr(), and others. > > I.e. it's a likely crap insertion vector; any patches around that thing > will require the same level of review as addition of a brand new syscall. Which is just how we should and hopefully treat any meaningful extension, yes. Otherwise let's just never add a flag argument to any syscall and only have dup()- and accept()-like syscalls. > And they will be harder to spot - consider the likely subjects for such > patches and compare to open addition of a new syscall... In the new revision I have dropped the atime argument because David already plumbed setting atime into fsmount() via flags and making userspace jump through more hoops by adding more constants seems pointless. So the additional arguments can be moved up because we're below the 6 syscall args limit. Though I really want to stress that while I see the worry it is less a technial argument but one for our review process where we should treat extensions to syscalls as strict as syscall additions. Which yes, very much so. Thanks! Christian