From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753862AbZHMJFp (ORCPT ); Thu, 13 Aug 2009 05:05:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753704AbZHMJFp (ORCPT ); Thu, 13 Aug 2009 05:05:45 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:48579 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752531AbZHMJFn (ORCPT ); Thu, 13 Aug 2009 05:05:43 -0400 To: Sukadev Bhattiprolu Cc: linux-kernel@vger.kernel.org, Oren Laadan , serue@us.ibm.com, Alexey Dobriyan , Pavel Emelyanov , Andrew Morton , torvalds@linux-foundation.org, mikew@google.com, mingo@elte.hu, hpa@zytor.com, Containers , sukadev@us.ibm.com, Oleg Nesterov References: <20090807061103.GA19343@us.ibm.com> <20090813080049.GA16639@us.ibm.com> From: ebiederm@xmission.com (Eric W. Biederman) Date: Thu, 13 Aug 2009 02:05:33 -0700 In-Reply-To: <20090813080049.GA16639@us.ibm.com> (Sukadev Bhattiprolu's message of "Thu\, 13 Aug 2009 01\:00\:49 -0700") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in02.mta.xmission.com;;;ip=76.21.114.89;;;frm=ebiederm@xmission.com;;;spf=neutral X-SA-Exim-Connect-IP: 76.21.114.89 X-SA-Exim-Rcpt-To: sukadev@linux.vnet.ibm.com, oleg@redhat.com, sukadev@us.ibm.com, containers@lists.linux-foundation.org, hpa@zytor.com, mingo@elte.hu, mikew@google.com, torvalds@linux-foundation.org, akpm@osdl.org, xemul@openvz.org, adobriyan@gmail.com, serue@us.ibm.com, orenl@cs.columbia.edu, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Sukadev Bhattiprolu X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 XMNoVowels Alpha-numberic number with no vowels * 1.5 TR_Symld_Words too many words that have symbols inside * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.0 T_TooManySym_03 6+ unique symbols in subject * 0.0 XM_SPF_Neutral SPF-Neutral * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.4 UNTRUSTED_Relay Comes from a non-trusted relay Subject: Re: [RFC][v4][PATCH 0/7] clone_with_pids() system call X-SA-Exim-Version: 4.2.1 (built Thu, 25 Oct 2007 00:26:12 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sukadev Bhattiprolu writes: > Eric W. Biederman [ebiederm@xmission.com] wrote: > | Sukadev Bhattiprolu writes: > | > | > === NEW CLONE() SYSTEM CALL: > | > > | > To support application checkpoint/restart, a task must have the same pid it > | > had when it was checkpointed. When containers are nested, the tasks within > | > the containers exist in multiple pid namespaces and hence have multiple pids > | > to specify during restart. > | > > | > This patchset implements a new system call, clone_with_pids() that lets a > | > process specify the pids of the child process. > | > > | > Patches 1 through 5 are helpers and we believe they are needed for application > | > restart, regardless of the kernel implementation of application restart. > | > | I'm not very impressed. > | > | - static int alloc_pidmap(struct pid_namespace *pid_ns) > | + static int alloc_pidmap(struct pid_namespace *pid_ns, int pid_max, int last_pid) > | > | Do that. > | > | That is pass in pid_max and last_pid, and you don't have to do weird > | things in alloc_pidmap, and no set_pidmap is needed. > > But last_pid is from the pid_ns. Do you mean to have alloc_pidmap() > take a pid_min and pid_max and when choosing a specific pid, have > pid_min == pid_max == target_pid ? Yes. It already takes a pid_min and a pid_max from the environment. I guess the pid_min is RESERVED_PIDS by default. > | No changes to copy_process are needed it already takes a struct pid > | argument. > > > I see your point about passing in both 'struct pid*' and target_pids[]. > But in the common case the struct pid passed into copy_process() is > NULL - allocating pid in do_fork() would significantly alter the > existing control flow - no ? alloc_pid() assumes any new pid namespace > has been created - in copy_namespaces(). Moving the alloc_pid() to > do_fork() would require parsing clone_flags in do_fork() and pulling > pid namespace code out of copy_namespaces(). Why change do_fork? > | I haven't been following closely what is gained by having a clone_with_pids > | syscall? > > When restarting an application from a checkpoint, the application must get > the same pid it had at the time of checkpoint. clone_with_pids() would be > used during restart so the child can be created with a specific set of pids. That part I understand. What I don't understand is why have that one part be special and have user space do the work? > | As for new namespaces that don't need to happen at process creation time > | (which is just about anything that is left) we can create a new syscall that > | unshares just that one. > | > > Ok. If all new namespaces can be handled with a variant of unshare(), we can > decouple clone_with_pids() from the clone-flags issue. What I mean is we should be able to get away things like: sys_new_timens(); Very very simple syscalls. One per each kind of namespace we want new instances of. Eric