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Re: [PATCH 0/13] Pid namespaces (OpenVZ view) [message #13397 is a reply to message #13343]

Fri, 25 May 2007 13:29

serue
Messages: 750
Registered: February 2006

Senior Member

Quoting Pavel Emelianov (xemul@openvz.org):
> Serge E. Hallyn wrote:
> > Quoting Eric W. Biederman (ebiederm@xmission.com):
> >> Pavel Emelianov <xemul@openvz.org> writes:
> >>
> >>> That's how OpenVZ sees the pid namespaces.
> >>>
> >>> The main idea is that kernel keeps operating with tasks pid
> >>> as it did before, but each task obtains one more pid for each
> >>> pid type - the virtual pid. When putting the pid to user or
> >>> getting the pid from it kernel operates with the virtual ones.
> >> Just a quick reaction.
> >>
> >> - I would very much like to see a minimum of 3 levels of pids,
> >> being supported. Otherwise it is easy to overlook some of the
> >> cases that are required to properly support nesting, which long
> >> terms seems important.
> >
> > Pavel,
> >
> > If I wanted to start a virtual server and in there start some checkpoint
> > restart jobs, so I start a new pid namespace inside the c/r job, what
> > will happen?
>
> What will happen with this namespace on restore? What pids will
> you assign to it in the parent (but not that init) namespace?

No, no, my question is earlier. Maybe my use of the term
"checkpoint/restart job" is confusing, so let me call it a "batch job"
instead, with the understanding that it is started with the intent of
being safely checkpoint/restartable later on.

So in the original batch job, started in a vserver, what will the pids
look like in the checkpoint/restart job?

But I think I know the answer - you'll leave vpid == pid for these
tasks, and only set vpid differently when restarting a job, since that's
when you really care?

So the only situation where there might be a shortcoming is when
restarting a job in a vserver?

-serge

> a. arbitrary: that means that you don't care that subgroup
> of tasks in the VS namespace. Thus why don't move them
> into separate namespace
> b. try to hold them as they were: this way is likely to fail
> and can work w/o namespaces at all.
>
> So what's your answer?
>
> > a. second pidns unshare is refused
> > b. second pidns unshare is allowed, but c/r job is not visible
> > from the virtual server (but is from the global pidns)
> > c. second pidns unshare is allowed, and somehow the c/r job
> > is visible from the virtual server
> >
> > If (a), is this a short-term shortcoming for simplicity of prototype and
> > code review, or do you think it's actually the right thing t do long
> > term?
> >
> > thanks,
> > -serge
> >
> >> - Semantically fork is easier then unshare. Unshare can mean
> >> a lot of things, and it is easy to pick a meaning that has weird
> >> side effects. Your implementation has a serious problem in that you
> >> change the value of getpid() at runtime. Glibc does not know how to
> >> cope with the value of getpid() changing.
> >>
> >> Eric
> >

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[Message index]

		[PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Thu, 24 May 2007 12:32
		[PATCH 1/13] Round up the API By: Pavel Emelianov on Thu, 24 May 2007 12:35
		Re: [PATCH 1/13] Round up the API By: serue on Thu, 24 May 2007 16:09
		Re: [PATCH 1/13] Round up the API By: ebiederm on Thu, 24 May 2007 16:22
		Re: [PATCH 1/13] Round up the API By: Pavel Emelianov on Thu, 24 May 2007 16:31
		Re: [PATCH 1/13] Round up the API By: serue on Thu, 24 May 2007 16:48
		Re: [PATCH 1/13] Round up the API By: Pavel Emelianov on Fri, 25 May 2007 07:00
		Re: [PATCH 1/13] Round up the API By: serue on Fri, 25 May 2007 13:02
		[PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Thu, 24 May 2007 12:37
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Thu, 24 May 2007 16:08
		Re: [PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Fri, 25 May 2007 06:58
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Fri, 25 May 2007 13:01
		Re: [PATCH 2/13] Small preparations for namespaces By: Pavel Emelianov on Fri, 25 May 2007 13:21
		Re: [PATCH 2/13] Small preparations for namespaces By: serue on Fri, 25 May 2007 13:55
		[PATCH 3/13] Introduciton of config option and clone flag By: Pavel Emelianov on Thu, 24 May 2007 12:42
		Re: [PATCH 3/13] Introduciton of config option and clone flag By: ebiederm on Thu, 24 May 2007 15:39
		[PATCH 4/13] Introduce the vpid fields and helpers for getting them By: Pavel Emelianov on Thu, 24 May 2007 12:44
		[PATCH 5/13] Expand the pid/task seeking functions set By: Pavel Emelianov on Thu, 24 May 2007 12:46
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Dave Hansen on Thu, 24 May 2007 17:11
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Pavel Emelianov on Fri, 25 May 2007 07:08
		Re: [PATCH 5/13] Expand the pid/task seeking functions set By: Sukadev Bhattiprolu on Fri, 25 May 2007 23:36
		[PATCH 6/13] Pid allocation/freeing procedures By: Pavel Emelianov on Thu, 24 May 2007 12:49
		[PATCH 7/13] Set virtual pids for a newly cloned task By: Pavel Emelianov on Thu, 24 May 2007 12:53
		[PATCH 8/13] The namespace cloning By: Pavel Emelianov on Thu, 24 May 2007 12:57
		[PATCH 9/13] Make proc be able to have multiple super blocks By: Pavel Emelianov on Thu, 24 May 2007 13:01
		[PATCH 10/13] Make proc draw pids from appropriate namespace By: Pavel Emelianov on Thu, 24 May 2007 13:04
		[PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 24 May 2007 13:06
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 24 May 2007 16:05
		Re: [PATCH 11/13] Changes to show virtual ids to user By: xemul on Thu, 24 May 2007 16:15
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 24 May 2007 16:33
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Fri, 25 May 2007 06:33
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Fri, 25 May 2007 15:48
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Cedric Le Goater on Tue, 29 May 2007 12:32
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 07:57
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 08:00
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 31 May 2007 11:26
		Re: [PATCH 11/13] Changes to show virtual ids to user By: Pavel Emelianov on Thu, 31 May 2007 11:46
		Re: [PATCH 11/13] Changes to show virtual ids to user By: ebiederm on Thu, 31 May 2007 13:41
		[PATCH 12/13] Show appropriate pids in proc By: Pavel Emelianov on Thu, 24 May 2007 13:08
		[PATCH 13/13] Make all proc entres accessible in a namespace By: Pavel Emelianov on Thu, 24 May 2007 13:13
		Instructions of how to make testing easy By: Pavel Emelianov on Thu, 24 May 2007 13:19
		Re: Instructions of how to make testing easy By: Pavel Emelianov on Thu, 24 May 2007 16:16
		Re: Instructions of how to make testing easy By: Cedric Le Goater on Thu, 24 May 2007 14:55
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 15:09
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: xemul on Thu, 24 May 2007 16:11
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 16:59
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 18:56
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 19:10
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:08
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 13:25
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 13:53
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 14:25
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Mon, 28 May 2007 07:48
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 04:30
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Tue, 29 May 2007 07:47
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 12:36
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:06
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Fri, 25 May 2007 14:55
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 16:00
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Thu, 24 May 2007 16:20
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 06:29
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: serue on Fri, 25 May 2007 13:29
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Thu, 24 May 2007 16:26
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Thu, 24 May 2007 19:18
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:15
		Re: Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: dev on Mon, 28 May 2007 11:50
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: ebiederm on Tue, 29 May 2007 13:07
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Daniel Lezcano on Thu, 24 May 2007 16:41
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Pavel Emelianov on Fri, 25 May 2007 07:26
		Re: [PATCH 0/13] Pid namespaces (OpenVZ view) By: Daniel Lezcano on Fri, 25 May 2007 08:30

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