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[2620:137:e000::1:20]) by mx.google.com with ESMTP id b17-20020a05640202d100b0051e3d383697si2205794edx.504.2023.07.11.07.17.09; Tue, 11 Jul 2023 07:17:34 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=uFC0KFw6; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233218AbjGKOBX (ORCPT + 99 others); Tue, 11 Jul 2023 10:01:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233182AbjGKOBV (ORCPT ); Tue, 11 Jul 2023 10:01:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B77DBB0; Tue, 11 Jul 2023 07:01:19 -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 554A861504; Tue, 11 Jul 2023 14:01:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ADD1DC433C7; Tue, 11 Jul 2023 14:01:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689084078; bh=cdE+rFjbrFVLmzVrU6vfdc/Au2vs/4K/KtQWUN2iOVE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uFC0KFw6/M6i8iNMypafGbl8Cu47AhRfSYX/xpea89PI4ZoMwe92EJqP3skNe1e6r wdNiag9bpyADI4zIDbvsfEfC5gi5cG0LiI+uy+iziLVFM+p32F6ViRjBHJmXzejh3K hGryvnrWcowWB4v9G6Utb47tLMTtfXf0Jk5KlXTXblJ68+Ehl7NBgEro6SYLZcBbuG SEhMMw8zZvhNH953cv8zDMYVJb4nE9cNKmW9VcGjlVykyXZpRuOY205drYPWTtbPxy Nee7XyVCXNFnj+xKEgPCEgPFhFOWJaEQgr+bospaDMUJydxlVz0ktUF8W7K96PF8x7 FoGj2nXcIV0Uw== Date: Tue, 11 Jul 2023 16:01:03 +0200 From: Christian Brauner To: Alexey Gladkov 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: <20230711-verpennen-turnier-717bb9682e19@brauner> References: <87o8pscpny.fsf@oldenburg2.str.redhat.com> <83363cbb-2431-4520-81a9-0d71f420cb36@app.fastmail.com> <20230711-demolieren-nilpferd-80ffe47563ad@brauner> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.