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=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 1000CECE587 for ; Mon, 14 Oct 2019 10:32:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E382220663 for ; Mon, 14 Oct 2019 10:32:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731470AbfJNKcJ (ORCPT ); Mon, 14 Oct 2019 06:32:09 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:34117 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731127AbfJNKcI (ORCPT ); Mon, 14 Oct 2019 06:32:08 -0400 Received: from [212.86.36.32] (helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1iJxdv-0001ho-5b; Mon, 14 Oct 2019 10:31:59 +0000 Date: Mon, 14 Oct 2019 12:31:58 +0200 From: Christian Brauner To: Christian Kellner Cc: jannh@google.com, aarcange@redhat.com, akpm@linux-foundation.org, cyphar@cyphar.com, elena.reshetova@intel.com, guro@fb.com, ldv@altlinux.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, mhocko@suse.com, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, viro@zeniv.linux.org.uk Subject: Re: [PATCH] pidfd: add NSpid entries to fdinfo Message-ID: <20191014103157.h2wph2ujjidsrhyw@wittgenstein> References: <20191012101922.24168-1-christian.brauner@ubuntu.com> <20191012102119.qq2adlnxjxrkslca@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 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 11:43:01AM +0200, Christian Kellner wrote: > On Sat, 2019-10-12 at 12:21 +0200, Christian Brauner wrote: > > I think this might be more what we want. > Yep, indeed. > > > 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"). > > > Christian, this is just a quick stab I took. Feel free to pick this > > up as a template. > Thanks! I slightly re-worked it, with the reasoning above in mind, to > get rid of one of the branches: Thanks! > > +#ifdef CONFIG_PID_NS > + seq_put_decimal_ull(m, "\nNSpid:\t", nr); > + if (nr) { > + int i; > + > + /* If nr is non-zero it means that 'pid' is valid and that > + * ns, i.e. the pid namespace associated with the procfs > + * instance, is in the pid namespace hierarchy of pid. > + * Start at one level below and print all descending pids. > + */ > + for (i = ns->level + 1; i <= pid->level; i++) { > + ns = pid->numbers[i].ns; I'm not a fan of overriding the "ns" pointer. It's not a huge deal but it's rather subtle. > + seq_put_decimal_ull(m, "\t", pid_nr_ns(pid, ns)); > + } > + } > +#endif > > But I now just realized that with the very same reasoning, if nr is > non-zero, we don't need to redo all the checks and can just do: > > for (i = ns->level + 1; i <= pid->level; i++) > seq_put_decimal_ull(m, "\t", pid->numbers[i].nr); > > If this sounds good to you I resend the patches with the change above. 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 Christian