From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751983AbaEaGHV (ORCPT ); Sat, 31 May 2014 02:07:21 -0400 Received: from mail-la0-f47.google.com ([209.85.215.47]:49371 "EHLO mail-la0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751121AbaEaGHT (ORCPT ); Sat, 31 May 2014 02:07:19 -0400 Date: Sat, 31 May 2014 10:07:13 +0400 From: Vasily Kulikov To: Pavel Emelyanov Cc: Richard Weinberger , containers@lists.linux-foundation.org, Serge Hallyn , linux-kernel@vger.kernel.org, Oleg Nesterov , David Howells , "Eric W. Biederman" , Andrew Morton , Al Viro Subject: Re: [PATCH v2] /proc/pid/status: show all sets of pid according to ns Message-ID: <20140531060713.GA5315@cachalot> References: <1401272683-1659-1-git-send-email-chenhanxiao@cn.fujitsu.com> <5385DA19.2060008@parallels.com> <20140528182824.GA5057@cachalot> <53863889.9080509@parallels.com> <20140529055954.GA10354@cachalot> <5386F8EA.8050501@parallels.com> <20140529111236.GA14576@cachalot> <53871A92.9000004@parallels.com> <20140529115946.GA19889@cachalot> <53872DAD.1070502@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <53872DAD.1070502@parallels.com> 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 On Thu, May 29, 2014 at 16:53 +0400, Pavel Emelyanov wrote: > On 05/29/2014 03:59 PM, Vasily Kulikov wrote: > > On Thu, May 29, 2014 at 15:31 +0400, Pavel Emelyanov wrote: > >> On 05/29/2014 03:12 PM, Vasily Kulikov wrote: > >>> On Thu, May 29, 2014 at 13:07 +0400, Pavel Emelyanov wrote: > >>>> On 05/29/2014 09:59 AM, Vasily Kulikov wrote: > >>>>> On Wed, May 28, 2014 at 23:27 +0400, Pavel Emelyanov wrote: > >>>>> ] 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. > >>>>> > >>>>> A new syscall might complicate trouble shooting by admin. > >>>> > >>>> Pure syscall -- yes. What if we teach the ps and top utilities to show additional > >>>> info? I think that would help. > >>> > >>> I like the idea with low level non-shell API which can be used by > >>> utility like ps (or implementation of a new tool to work with complex > >>> namespace hierarchies). It should fit for troublesooting. Then there > >>> should be no reason to implement two different APIs for observation from > >>> shell via FS and from applications. > >> > >> Maybe we can reuse the existing kcmp() system call? We would have to store > >> the collected pid values in some hash/tree anyway, and kcmp() provides us > >> good comparing function for doing this. > >> > >> Like we can call kcmp(pid1, pid2, KCMP_PID, nsfd1, nsfd2) which will mean > >> "Are tasks with pid1 in namespace pointed by nsfd1 and with pid2 in namespace > >> nsfd2 the same?" > >> > >> What do you think? > > > > kcmp() is not needed, just compare inode numbers: > > > > # ls -il /proc/{43,self}/ns/mnt > > 208182 lrwxrwxrwx 1 root root 0 мая 29 15:52 /proc/43/ns/mnt -> mnt:[4026531856] > > 216556 lrwxrwxrwx 1 root root 0 мая 29 15:57 /proc/self/ns/mnt -> mnt:[4026531840] > > But that's for comparing the namespaces, while I'm proposing the kcmp to > check for PIDs. Hm, right. What about the following solution: export global process ID (PID in init ns) which is visible inside of any namespace. Then you can compare numbers regardless in what namespace you are. -- Vasily Kulikov http://www.openwall.com - bringing security into open computing environments