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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 19A36C43461 for ; Thu, 10 Sep 2020 16:34:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBBEB214F1 for ; Thu, 10 Sep 2020 16:34:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727026AbgIJQe3 (ORCPT ); Thu, 10 Sep 2020 12:34:29 -0400 Received: from brightrain.aerifal.cx ([216.12.86.13]:52454 "EHLO brightrain.aerifal.cx" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726675AbgIJQdg (ORCPT ); Thu, 10 Sep 2020 12:33:36 -0400 Date: Thu, 10 Sep 2020 11:45:17 -0400 From: Rich Felker To: Al Viro Cc: linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vfs: add fchmodat2 syscall Message-ID: <20200910154516.GH3265@brightrain.aerifal.cx> References: <20200910142335.GG3265@brightrain.aerifal.cx> <20200910151828.GD1236603@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200910151828.GD1236603@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Sep 10, 2020 at 04:18:28PM +0100, Al Viro wrote: > On Thu, Sep 10, 2020 at 10:23:37AM -0400, Rich Felker wrote: > > > It was determined (see glibc issue #14578 and commit a492b1e5ef) that, > > on some filesystems, performing chmod on the link itself produces a > > change in the inode's access mode, but returns an EOPNOTSUPP error. > > Which filesystem types are those? It's been a long time and I don't know if the details were recorded. It was reported for xfs but I believe we later found it happening for others. See: https://sourceware.org/bugzilla/show_bug.cgi?id=14578#c17 https://sourceware.org/legacy-ml/libc-alpha/2020-02/msg00467.html and especially: https://sourceware.org/legacy-ml/libc-alpha/2020-02/msg00518.html where Christoph seems to have endorsed the approach in my patch. I'm fine with doing it differently if you'd prefer, though. Rich