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=-3.8 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 C5F86C433DB for ; Sun, 24 Jan 2021 02:00:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8AA5E227BF for ; Sun, 24 Jan 2021 02:00:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726484AbhAXCAF (ORCPT ); Sat, 23 Jan 2021 21:00:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56962 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726288AbhAXCAC (ORCPT ); Sat, 23 Jan 2021 21:00:02 -0500 Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [IPv6:2607:5300:60:148a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F3D6C0613D6 for ; Sat, 23 Jan 2021 17:59:22 -0800 (PST) Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94 #2 (Red Hat Linux)) id 1l3UgD-005Cgl-3r; Sun, 24 Jan 2021 01:59:05 +0000 Date: Sun, 24 Jan 2021 01:59:05 +0000 From: Al Viro To: Andres Freund Cc: Lennert Buytenhek , Jens Axboe , linux-kernel@vger.kernel.org, io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org Subject: Re: [RFC PATCH] io_uring: add support for IORING_OP_GETDENTS64 Message-ID: <20210124015905.GH740243@zeniv-ca> References: <20210123114152.GA120281@wantstofly.org> <20210123235055.azmz5jm2lwyujygc@alap3.anarazel.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210123235055.azmz5jm2lwyujygc@alap3.anarazel.de> Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 23, 2021 at 03:50:55PM -0800, Andres Freund wrote: > As there's only a shared lock, seems like both would end up with the > same ctx->pos and end up updating f_pos to the same offset (assuming the > same count). > > Am I missing something? This: f = fdget_pos(fd); if (!f.file) return -EBADF; in the callers. Protection of struct file contents belongs to struct file, *not* struct inode. Specifically, file->f_pos_lock. *IF* struct file in question happens to be shared and the file is a regular or directory (sockets don't need any exclusion on read(2), etc.)