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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 296CDECE587 for ; Mon, 14 Oct 2019 15:10:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 03AE82133F for ; Mon, 14 Oct 2019 15:10:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eL0KkC/q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733270AbfJNPKa (ORCPT ); Mon, 14 Oct 2019 11:10:30 -0400 Received: from mail-oi1-f195.google.com ([209.85.167.195]:45934 "EHLO mail-oi1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732647AbfJNPKa (ORCPT ); Mon, 14 Oct 2019 11:10:30 -0400 Received: by mail-oi1-f195.google.com with SMTP id o205so14004077oib.12 for ; Mon, 14 Oct 2019 08:10:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=n8mZzQYgCJoh/U/LtDTWoqHWL38rFTI9nqBb83t1F0I=; b=eL0KkC/qG5Sqdy3584kkE+iz33uqISxvsXEGdERUa7Qba35awyW4wPPpCaQDK4Vf1r A3DLF2XrRN3Lwh4n2M6qxwxu2T46oy32FbABZOdyiBDH2LNz67ggJr+I5OhDY4eeapth bIGYmB1CSf53TZI51DGqJab6Wjwy5z7eYIb7P7XsOHgHr1mbV/Jf08+om+Jr88+Wba5R oTzg3htSuDlhpSRZS3B1U76DkyOGgI+M99HxgN9w9xoR6tCXMFWhLG44qctxm9vFjIrm 5i5FtAqJuGamLA8VvOY1RqJRFB8jEkEhrNIziL8n1p3hBxPQloscS8mtFR/Ak1n5qkBB 6+dQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=n8mZzQYgCJoh/U/LtDTWoqHWL38rFTI9nqBb83t1F0I=; b=XPsqaJg2EHVz5otrhNea3Eyto55GeZ1rFSnl9AU1h9tZn8DX2lgKlsYYZcgHxd+XXJ J8OPdkVKRgjLyq4Nj0nM2Lu1MB1hDTM51+Tj1wKrfK52P8S6CI2hLqiiAK1PBVyCcdP0 kh0ETHxmXe92YEkJcS8mvnyzI65wdCgD6YyFQE9SMIoZHa7y6xPtl07nj4N37lXF3n10 mPsj22//lrzK9HZxxHFbNfr+qYYxDRryfvXeEu2CvjCFKAAgNf0lonkmzYA+5f9VjzO9 coEDwTHR5yf0u1Wa6RiIGHQF59vJHPrf5EXk1J/cR1qd7EuNsot2dnFwpBj1R4l6t30a 16nQ== X-Gm-Message-State: APjAAAXVBiYMGfBEgjCPBehHdHARn61S2kLzH7AYmrLgIoHVtl3IDHFB 0U2SCO9phgyAg6MAfVxx/kwwiliCz76SzaSjurscfA== X-Google-Smtp-Source: APXvYqzcVFFImqZI58K41aEG21TM6C60Hd0B7GL6/+3YeLE94vV5SzMbABckyJbt3DVKWbg2bM0mT6UlrjQp+Ume+Q4= X-Received: by 2002:a05:6808:95:: with SMTP id s21mr25075773oic.68.1571065827544; Mon, 14 Oct 2019 08:10:27 -0700 (PDT) MIME-Version: 1.0 References: <20191012101922.24168-1-christian.brauner@ubuntu.com> <20191012102119.qq2adlnxjxrkslca@wittgenstein> <20191014103157.h2wph2ujjidsrhyw@wittgenstein> In-Reply-To: <20191014103157.h2wph2ujjidsrhyw@wittgenstein> From: Jann Horn Date: Mon, 14 Oct 2019 17:10:01 +0200 Message-ID: Subject: Re: [PATCH] pidfd: add NSpid entries to fdinfo To: Christian Brauner Cc: Christian Kellner , Andrea Arcangeli , Andrew Morton , Aleksa Sarai , Elena Reshetova , Roman Gushchin , "Dmitry V. Levin" , Linux API , kernel list , Michal Hocko , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Al Viro Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 14, 2019 at 12:32 PM Christian Brauner wrote: > On Mon, Oct 14, 2019 at 11:43:01AM +0200, Christian Kellner wrote: > > On Sat, 2019-10-12 at 12:21 +0200, Christian Brauner wrote: > > > I tried to think of cases where the first entry of Pid is not > > > identical > > > to the first entry of NSpid but I came up with none. Maybe you do, > > > Jann? > > Yeah, I don't think that can be the case. By looking at the source of > > 'pid_nr_ns(pid, ns)' a non-zero return means that a) 'pid' valid, ie. > > non-null and b) 'ns' is in the pid namespace hierarchy of 'pid' (at > > pid->level, i.e. "pid->numbers[ns->level].ns == ns"). Agreed. > You could probably do: > > #ifdef CONFIG_PID_NS > seq_put_decimal_ull(m, "\nNSpid:\t", nr); > for (i = ns->level + 1; i <= pid->level && nr; i++) > seq_put_decimal_ull(m, "\t", pid->numbers[i].nr); > #endif Personally, I dislike hiding the precondition for running the loop in the loop statement like that. While it makes the code more concise, it somewhat obfuscates the high-level logic at a first glance.