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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D0EE5C433E0 for ; Tue, 2 Jun 2020 23:37:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AFA8620663 for ; Tue, 2 Jun 2020 23:37:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728306AbgFBXhy (ORCPT ); Tue, 2 Jun 2020 19:37:54 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54659 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726223AbgFBXhx (ORCPT ); Tue, 2 Jun 2020 19:37:53 -0400 Received: from ip5f5af183.dynamic.kabel-deutschland.de ([95.90.241.131] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jgGTe-000281-Ps; Tue, 02 Jun 2020 23:37:50 +0000 Date: Wed, 3 Jun 2020 01:37:49 +0200 From: Christian Brauner To: Florian Weimer Cc: torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, Kyle Evans , Victor Stinner , viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, fweimer@redhat.com, jannh@google.com, oleg@redhat.com, arnd@arndb.de, shuah@kernel.org, dhowells@redhat.com, ldv@altlinux.org Subject: Re: [PATCH v5 1/3] open: add close_range() Message-ID: <20200602233749.mo65o2enokiypwiz@wittgenstein> References: <20200602204219.186620-1-christian.brauner@ubuntu.com> <20200602204219.186620-2-christian.brauner@ubuntu.com> <87d06hdozy.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87d06hdozy.fsf@mid.deneb.enyo.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 03, 2020 at 01:30:57AM +0200, Florian Weimer wrote: > * Christian Brauner: > > > The performance is striking. For good measure, comparing the following > > simple close_all_fds() userspace implementation that is essentially just > > glibc's version in [6]: > > > > static int close_all_fds(void) > > { > > int dir_fd; > > DIR *dir; > > struct dirent *direntp; > > > > dir = opendir("/proc/self/fd"); > > if (!dir) > > return -1; > > dir_fd = dirfd(dir); > > while ((direntp = readdir(dir))) { > > int fd; > > if (strcmp(direntp->d_name, ".") == 0) > > continue; > > if (strcmp(direntp->d_name, "..") == 0) > > continue; > > fd = atoi(direntp->d_name); > > if (fd == dir_fd || fd == 0 || fd == 1 || fd == 2) > > continue; > > close(fd); > > } > > closedir(dir); > > return 0; > > } > > > > > [6]: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/grantpt.c;h=2030e07fa6e652aac32c775b8c6e005844c3c4eb;hb=HEAD#l17 > > Note that this is an internal implementation that is not exported. > > Currently, libc seems to not provide an exported version of this > > because of missing kernel support to do this. > > Just to be clear, this code is not compiled into glibc anymore in > typical configurations. I have posted a patch to turn grantpt into a > no-op: That's great! (I remember commenting on that thread.)