Re: [RFC][PATCH 7/7][v2] Define clone_with_pids syscall

[Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>]

Sukadev Bhattiprolu wrote:
> Sukadev Bhattiprolu [sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org] wrote:
> | Oren Laadan [orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org] wrote:
> 
> I am not sure what the semantics should be for this case:
> 
> 	- checkpoint a process that is in level-3 pid namespace
> 	- restart in a level-2 or level-1 pid namespace
> 

Meaning: a container root was at level-3, so tasks in the container
were level-3 through level-(3+N), where N is the in-container depth
so to speak. Then it was restarted such that the base became level-2
or level-1.

I think we already covered this.

> clone_with_pids() will fail now since number of pids specified would
> be 4 but kernel expects only 2 or 3. mktree/restart program cannot
> figure out current nesting to trim the target-pids.
> 
> Should we remove the check of user-pids exceeding the current nesting
> level and simply ignore the pids from the older namespaces ?

It seems to me that the current behavior is correct: I can't think
of a case where trimming (silently) would make sense, or where
a program would end up giving more pids that it's nesting level.

Oren.