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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 639A3C3F2C6 for ; Tue, 3 Mar 2020 19:23:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3BC39208C3 for ; Tue, 3 Mar 2020 19:23:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="cUtFbLLA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730305AbgCCTXT (ORCPT ); Tue, 3 Mar 2020 14:23:19 -0500 Received: from mail-il1-f195.google.com ([209.85.166.195]:37434 "EHLO mail-il1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729458AbgCCTXT (ORCPT ); Tue, 3 Mar 2020 14:23:19 -0500 Received: by mail-il1-f195.google.com with SMTP id a6so3828664ilc.4 for ; Tue, 03 Mar 2020 11:23:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=KiZbLVn4oUdQq37v8gihe8HTdDkjhp2c0YGGCKWw9Xs=; b=cUtFbLLAYh6gx9tm2hX9XXTHNvQbYYtQzHRgoECvT1iNpNhnaqHdzCG/CIyEeLM4gL Z1ePPKxytHV6jrshCuDSCg/F/Y3EhjB789IMGMhvLY5BjMF12XYa9P1fenpGS3wnUpiq 2ub+HBTb161Oel2xhswKj/mAZyHisH25WZK9vbaxjY6LTd9Hw0LO3CFy6e1A4xK6Rp8h B5RYOBiOga3ZtJu6UFkd/mh/wq7qjfsVdp483vXbAO26p9+WfSM398uJZlbzilANoMKh Fc8hK9CXNYQpui0/BpLv6RVXEYpV8KRigcO4x7aUkA1YZ0R/2aAWKkiiGy9dpnCH8Mco ACqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=KiZbLVn4oUdQq37v8gihe8HTdDkjhp2c0YGGCKWw9Xs=; b=I0pGZV+QO2R8O/kWZuldolN+dZKIra3jv7xegyM56GJ3U13nhEUQ9h1VtUdbAHtP4p TEcNEG/kTF/08/lsNydhA1ETWB+73db71ElrRGJ9ZXL+s64eGRgsFaTgVu+mF9XdX294 9G7MMHjxgNG1ON9J/M8eHuU9So1cAHu90h6vJEt2R7VEkj5JH9G2sEQbYs8BPJDuiXBv TsMAdeMvtf+ywcrSaljQz/vVekg/0bQm3VU8WFK79RczXYhMB4qMPu8xXECImAZsiH6v m8HIL525ZHNowvqAuQzWQCrRWXKss/PVhQhsF9qbjbwN4VQiaYbmjvjBcoiYZ8Zp9YmI kbgA== X-Gm-Message-State: ANhLgQ18U/Lnx0zOQyjVKW9FRjwrJ/QK4fc+E6W1avuQSgrGTHCN2zE+ o7oXmwk8jnSdPgH/w9fqRSIeWw== X-Google-Smtp-Source: ADFU+vsGYrEKxsUpTqs5b+dGZi3gm2OTFxMN1tCOScyWlCXapZO1C3KKgpKNsVOR0wDn9xAFuJJT4A== X-Received: by 2002:a92:9507:: with SMTP id y7mr1729545ilh.243.1583263398611; Tue, 03 Mar 2020 11:23:18 -0800 (PST) Received: from [192.168.1.159] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id f72sm8161736ilg.84.2020.03.03.11.23.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Mar 2020 11:23:18 -0800 (PST) Subject: Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17] To: Jeff Layton , Greg Kroah-Hartman , Jann Horn Cc: Miklos Szeredi , Karel Zak , David Howells , Ian Kent , Christian Brauner , James Bottomley , Steven Whitehouse , Miklos Szeredi , viro , Christian Brauner , "Darrick J. Wong" , Linux API , linux-fsdevel , lkml References: <1509948.1583226773@warthog.procyon.org.uk> <20200303113814.rsqhljkch6tgorpu@ws.net.home> <20200303130347.GA2302029@kroah.com> <20200303131434.GA2373427@kroah.com> <20200303134316.GA2509660@kroah.com> <20200303141030.GA2811@kroah.com> <20200303142407.GA47158@kroah.com> <030888a2-db3e-919d-d8ef-79dcc10779f9@kernel.dk> <7a05adc8-1ca9-c900-7b24-305f1b3a9b86@kernel.dk> From: Jens Axboe Message-ID: Date: Tue, 3 Mar 2020 12:23:16 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 3/3/20 12:02 PM, Jeff Layton wrote: > Basically, all you'd need to do is keep a pointer to struct file in the > internal state for the chain. Then, allow userland to specify some magic > fd value for subsequent chained operations that says to use that instead > of consulting the fdtable. Maybe use -4096 (-MAX_ERRNO - 1)? BTW, I think we need two magics here. One that says "result from previous is fd for next", and one that says "fd from previous is fd for next". The former allows inheritance from open -> read, the latter from read -> write. -- Jens Axboe