From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758306AbcG0Epm (ORCPT ); Wed, 27 Jul 2016 00:45:42 -0400 Received: from mail-eopbgr40116.outbound.protection.outlook.com ([40.107.4.116]:65184 "EHLO EUR03-DB5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750701AbcG0Epk (ORCPT ); Wed, 27 Jul 2016 00:45:40 -0400 X-Greylist: delayed 3650 seconds by postgrey-1.27 at vger.kernel.org; Wed, 27 Jul 2016 00:45:39 EDT Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=avagin@virtuozzo.com; Date: Tue, 26 Jul 2016 12:11:02 -0700 From: Andrew Vagin To: "W. Trevor King" CC: "Michael Kerrisk (man-pages)" , Serge Hallyn , Andrey Vagin , Linux API , Linux Containers , LKML , "criu@openvz.org" , "Eric W. Biederman" , linux-fsdevel , "James Bottomley" , Alexander Viro Subject: Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces Message-ID: <20160726191101.GB328@outlook.office365.com> References: <1515f5f2-5a49-fcab-61f4-8b627d3ba3e2@gmail.com> <87lh0pg8jx.fsf@x220.int.ebiederm.org> <44ca0e41-dc92-45b1-2a6c-c41a048a072d@gmail.com> <87r3ahepb4.fsf@x220.int.ebiederm.org> <20160726025455.GC26206@outlook.office365.com> <3390535b-0660-757f-aeba-c03d936b3485@gmail.com> <20160726182524.GA328@outlook.office365.com> <20160726183224.GN24913@odin.tremily.us> MIME-Version: 1.0 Content-Type: text/plain; charset="koi8-r" Content-Disposition: inline In-Reply-To: <20160726183224.GN24913@odin.tremily.us> User-Agent: Mutt/1.6.2 (2016-07-01) X-Originating-IP: [162.246.95.100] X-ClientProxiedBy: BY2PR04CA0075.namprd04.prod.outlook.com (10.255.247.43) To HE1PR0801MB1977.eurprd08.prod.outlook.com (10.168.94.147) X-MS-Office365-Filtering-Correlation-Id: f7dfaeb2-7f2f-4121-6622-08d3b588a335 X-Microsoft-Exchange-Diagnostics: 1;HE1PR0801MB1977;2:6XOe483UHs+O6C9su8QFLr9xL5EJlBDhT/VRz+mesMfpph8teOBmtduFpLKMLwN5nLqTn33dpYk5J8hBj2ItEYSJ7JNij44xlPo3nMHV3eaDkDB5kEnLT0Ri7sceLg+IQHobQ4LgEU/xsfcn+11qVspsNT5501ShY7COb8f70e6yIBM0laa8DvqT5Wq0lxFU;3:KKQNCf0DSgLIcWfIxvMNJyiQRHrKJWc2pOFK7jbvlY9Z9amJjnNU7yhs6ca/jRbZJ3bLjtHcZcW+CExn4EDImRHRPSUOsjc/9gwwmiwsmtQQt3J4UfiW0rFa9cBtDbFK;25:Ye4LdHwAjRAdYOP+paz+JNqvpi+ugL0f6ugR9wRPuEgA1dxikHoJ769cZ1uOvleSwuqIUFwrXyVHS5rWQAjMxpy7mVcIBWTDzos9zzq+QmgCjAGNfVfpIc6bByw2rCBV9leCzL9JcKRFc0m0D7OFJeFUVlRHxeIpsW1bm21bCB9Bnb8HdJDmFY+DZqrQYLjd2E7JLRi5SnVWc523xxIoQwMf+E+9xGQhXpQWCXVw1n8P/CzT0URwO6wVoSjHwfVSG2Hj5zwyZhIMwNFjcQGzJ4xOqvn/fpu6UqK++6hd29qA8tjTarjCQSbFNCu7x8o7JyQvVqa8Z2lXSCyOkJWbQFMOjnI/XqZDwjXpZy1sywnM/QPRo+yF1VwE7W+D0EGLqNAu/+pr1NPaQFQKBdOHCnDKQosfpjl1RGOAm/LOFqQ= X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:HE1PR0801MB1977; 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Trevor King wrote: > On Tue, Jul 26, 2016 at 11:25:24AM -0700, Andrew Vagin wrote: > > Sure. If a process wants to compare two namespaces, it needs to get file > > descriptors for them (open /proc/PID/ns/XXX, use new ioctl-s, find a > > process which has them), > > and then it calls kcmp(pid1, pid2, KCMP_NSFD, ns_fd1, ns_fd2) > > If you use the new ioctl-s to get ns_fd2, do you walk your local /proc > to find pid2? If you use the new ioctl-s to get nf_fd2, you will have it in the current process, so pid2 will be getpid(). pidX identifies a process where to find fdX. man 2 kcmp: The kcmp() system call can be used to check whether the two processes identified by pid1 and pid2 share a kernel resource such as virtual memory, file descriptors, and so on. > > Cheers, > Trevor > > -- > This email may be signed or encrypted with GnuPG (http://www.gnupg.org). > For more information, see http://en.wikipedia.org/wiki/Pretty_Good_Privacy