From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754330AbaFWNcg (ORCPT ); Mon, 23 Jun 2014 09:32:36 -0400 Received: from static.92.5.9.176.clients.your-server.de ([176.9.5.92]:46286 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754462AbaFWNcc (ORCPT ); Mon, 23 Jun 2014 09:32:32 -0400 Date: Mon, 23 Jun 2014 15:32:30 +0200 From: "Serge E. Hallyn" To: "chenhanxiao@cn.fujitsu.com" Cc: Richard Weinberger , "containers@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , Pavel Emelyanov , "linux-api@vger.kernel.org" , Serge Hallyn , Oleg Nesterov , David Howells , "Eric W. Biederman" , Al Viro Subject: Re: [PATCH v2] ns: introduce getnspid syscall Message-ID: <20140623133230.GA31817@mail.hallyn.com> References: <1403259512-10510-1-git-send-email-chenhanxiao@cn.fujitsu.com> <53A414B2.20108@nod.at> <5871495633F38949900D2BF2DC04883E54ECC5@G08CNEXMBPEKD02.g08.fujitsu.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5871495633F38949900D2BF2DC04883E54ECC5@G08CNEXMBPEKD02.g08.fujitsu.local> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting chenhanxiao@cn.fujitsu.com (chenhanxiao@cn.fujitsu.com): > Hi > > > -----Original Message----- > > From: Richard Weinberger [mailto:richard@nod.at] > > Sent: Friday, June 20, 2014 7:02 PM > > To: Chen, Hanxiao/陈 晗霄; containers@lists.linux-foundation.org; > > linux-kernel@vger.kernel.org > > Cc: Eric W. Biederman; Serge Hallyn; Daniel P. Berrange; Oleg Nesterov; Al Viro; > > David Howells; Pavel Emelyanov; Vasiliy Kulikov; Gotou, Yasunori/五島 康文; > > linux-api@vger.kernel.org > > Subject: Re: [PATCH v2] ns: introduce getnspid syscall > > > > Am 20.06.2014 12:18, schrieb Chen Hanxiao: > > > We need a direct method of getting the pid inside containers. > > > If some issues occurred inside container guest, host user > > > could not know which process is in trouble just by guest pid: > > > the users of container guest only knew the pid inside containers. > > > This will bring obstacle for trouble shooting. > > > > > > int getnspid(pid_t pid, int fd1, int fd2); > > > > > > pid: the pid number need to be translated. > > > > > > fd: a file descriptor referring to one of > > > the namespace entries in a /proc/[pid]/ns/pid. > > > fd1 for destination ns(ns1), where the pid came from. > > > fd2 for reference ns(ns2), while fd2 = -2 means for current ns. > > > > > > return value: > > > >0 : translated pid in ns1(fd1) seen from ns2(fd2). > > > <=0: on failure. > > > > > > > I don't think that adding a new system call for this is a good solution. > > We need a more generic way. I bet people are interested in more than just PID > > numbers. > > Could you please give some hints on how to expand this interface? > > > > > I agree with Eric that a procfs solution is more appropriate. > > > > Procfs is a good solution, but syscall is not bad though. I might be inclined to agree, except that in this case you are still needing mounted procfs anyway to get the proc/$pid/ns/pid fds. I'm sorry, I've not been watching this thread, so this probably has been considered and decided against, but I'm going to ask anyway. Keeping in mind both checkpoint-restart and and introspection for use in a setns'd commend, why not make it pid_t getnspid(pid_t query_pid, pid_t observer_pid) which returns the process id of query_pid as seen from observer_pid's pidns? > Procfs works for me, but that seems could not fit > Pavel's requirement. > His opinion is that a syscall is a more generic interface > than proc files, and also very helpful. > And syscall could tell whether a pid lives in a specific pid namespace, > much convenient than procfs. > > Thanks, > - Chen > _______________________________________________ > Containers mailing list > Containers@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/containers