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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD94BC001E0 for ; Tue, 11 Jul 2023 15:24:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231919AbjGKPYQ (ORCPT ); Tue, 11 Jul 2023 11:24:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41162 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231846AbjGKPYO (ORCPT ); Tue, 11 Jul 2023 11:24:14 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FA5B10D4; Tue, 11 Jul 2023 08:24:13 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0D3C96155C; Tue, 11 Jul 2023 15:24:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46E26C433C8; Tue, 11 Jul 2023 15:23:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689089052; bh=nyE4suotIowU8lKnKt+Umw+WI2Pk9iMcLZepBf+apY8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oEo8yqXLBQcJ016nZmVI6o/nx3t9By5un0RV4fbIKnHDk0VPSpp+yaNMirBtqzWpT bol75aJRCGOWCT+N9yMrkrQVwEwDB8XWpgODtk3yI+ILPLq5smsYwABPzHWMi/M7KG kUQJPylWrx/7Ql611uTnEHF8Ca7MkikIUy5rcrlWGkGARPI3nHILM6AFuZYEin+imM n1HaEaVU7q0NQmuz7v6I6ZbkSVwp4NjRBykveJpCllqGcxPS/L657fKrCDqE1FNaLz 6d5tD55ouC0ebYXHDNhkXWIbv52u/QY77xgQ0vpiUD4ePJr/j3HQZKSAuDU9No0IwC 1j5Imns1pImTQ== Date: Tue, 11 Jul 2023 17:23:50 +0200 From: Alexey Gladkov To: Christian Brauner Cc: Arnd Bergmann , LKML , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, Alexander Viro , Palmer Dabbelt , "James E . J . Bottomley" , Arnaldo Carvalho de Melo , Alexander Shishkin , Jens Axboe , Benjamin Herrenschmidt , Christian Borntraeger , Borislav Petkov , Catalin Marinas , christian@brauner.io, Rich Felker , "David S . Miller" , Deepa Dinamani , Helge Deller , David Howells , fenghua.yu@intel.com, firoz.khan@linaro.org, Florian Weimer , Geert Uytterhoeven , glebfm@altlinux.org, gor@linux.ibm.com, hare@suse.com, heiko.carstens@de.ibm.com, "H. Peter Anvin" , Ivan Kokshaysky , jhogan@kernel.org, Kim Phillips , ldv@altlinux.org, linux-alpha@vger.kernel.org, Linux-Arch , linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, Russell King , linuxppc-dev@lists.ozlabs.org, Andy Lutomirski , Matt Turner , Ingo Molnar , Michal Simek , Michael Ellerman , Namhyung Kim , paul.burton@mips.com, Paul Mackerras , Peter Zijlstra , ralf@linux-mips.org, rth@twiddle.net, schwidefsky@de.ibm.com, sparclinux@vger.kernel.org, stefan@agner.ch, Thomas Gleixner , Tony Luck , tycho@tycho.ws, Will Deacon , x86@kernel.org, Yoshinori Sato Subject: Re: [PATCH v3 2/5] fs: Add fchmodat4() Message-ID: References: <87o8pscpny.fsf@oldenburg2.str.redhat.com> <83363cbb-2431-4520-81a9-0d71f420cb36@app.fastmail.com> <20230711-demolieren-nilpferd-80ffe47563ad@brauner> <20230711-verpennen-turnier-717bb9682e19@brauner> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230711-verpennen-turnier-717bb9682e19@brauner> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Jul 11, 2023 at 04:01:03PM +0200, Christian Brauner wrote: > On Tue, Jul 11, 2023 at 02:51:01PM +0200, Alexey Gladkov wrote: > > On Tue, Jul 11, 2023 at 01:52:01PM +0200, Christian Brauner wrote: > > > On Tue, Jul 11, 2023 at 01:42:19PM +0200, Arnd Bergmann wrote: > > > > On Tue, Jul 11, 2023, at 13:25, Alexey Gladkov wrote: > > > > > From: Palmer Dabbelt > > > > > > > > > > On the userspace side fchmodat(3) is implemented as a wrapper > > > > > function which implements the POSIX-specified interface. This > > > > > interface differs from the underlying kernel system call, which does not > > > > > have a flags argument. Most implementations require procfs [1][2]. > > > > > > > > > > There doesn't appear to be a good userspace workaround for this issue > > > > > but the implementation in the kernel is pretty straight-forward. > > > > > > > > > > The new fchmodat4() syscall allows to pass the AT_SYMLINK_NOFOLLOW flag, > > > > > unlike existing fchmodat. > > > > > > > > > > [1] > > > > > https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/fchmodat.c;h=17eca54051ee28ba1ec3f9aed170a62630959143;hb=a492b1e5ef7ab50c6fdd4e4e9879ea5569ab0a6c#l35 > > > > > [2] > > > > > https://git.musl-libc.org/cgit/musl/tree/src/stat/fchmodat.c?id=718f363bc2067b6487900eddc9180c84e7739f80#n28 > > > > > > > > > > Signed-off-by: Palmer Dabbelt > > > > > Signed-off-by: Alexey Gladkov > > > > > > > > I don't know the history of why we ended up with the different > > > > interface, or whether this was done intentionally in the kernel > > > > or if we want this syscall. > > > > > > > > Assuming this is in fact needed, I double-checked that the > > > > implementation looks correct to me and is portable to all the > > > > architectures, without the need for a compat wrapper. > > > > > > > > Acked-by: Arnd Bergmann > > > > > > The system call itself is useful afaict. But please, > > > > > > s/fchmodat4/fchmodat2/ > > > > Sure. I will. > > Thanks. Can you also wire this up for every architecture, please? > I don't see that this has been done in this series. Sure. I have already added in all architectures as far as I can tell: $ diff -s <(find arch/ -name '*.tbl' |sort -u) <(git grep -lw fchmodat2 arch/ |sort -u) Files /dev/fd/63 and /dev/fd/62 are identical -- Rgrds, legion