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 00E7DC04FDF for ; Tue, 11 Jul 2023 11:52:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230182AbjGKLwX (ORCPT ); Tue, 11 Jul 2023 07:52:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229612AbjGKLwS (ORCPT ); Tue, 11 Jul 2023 07:52:18 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25AE6B1; Tue, 11 Jul 2023 04:52:17 -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 AD68D61461; Tue, 11 Jul 2023 11:52:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00B5DC433C8; Tue, 11 Jul 2023 11:52:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689076336; bh=FEYwsW8eEVWKaDxjSpsLJzH203pRDz88SghdcKEI1Cc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=djo5kRUxcwGp9ZdqEH8AfNMhg0qsCG7bCvPx452SCCqbjaEm9+RUsFZgu/4Zib58z 5wxZbVUvaLPjWynxuO9RjNWPxwRPiLlpBdpq7u67qP6VP0a5PV7Uq/N8eVnqF7Ktse bN/LatBa45dmE7fM0H3vOwVGIv+ESV5MlxzwYjjKXjjGFgQCBBr1R1dqqxW1RDhTHc BWhV6dQRSlMUIxiZQOE2JLF8NE1hMXxoZ08a4cE6AuaFymusAbOhm10YCvIc5/7Agj whDEvFt+uIB5AOK9f11RR8rXlvAFr5opLcAF5l/puWqcOG6Aj8zCTnMsnaYx+/nGRM iFCAZ/+dDnSMg== Date: Tue, 11 Jul 2023 13:52:01 +0200 From: Christian Brauner To: Arnd Bergmann Cc: Alexey Gladkov , 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: <20230711-demolieren-nilpferd-80ffe47563ad@brauner> References: <87o8pscpny.fsf@oldenburg2.str.redhat.com> <83363cbb-2431-4520-81a9-0d71f420cb36@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <83363cbb-2431-4520-81a9-0d71f420cb36@app.fastmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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/ With very few exceptions we don't version by argument number but by revision and we should stick to one scheme: openat()->openat2() eventfd()->eventfd2() clone()/clone2()->clone3() dup()->dup2()->dup3() // coincides with nr of arguments pipe()->pipe2() // coincides with nr of arguments renameat()->renameat2()