Re: [RFC][PATCH] ns: Syscalls for better namespace sharing control.

[ebiederm@xmission.com (Eric W. Biederman)]

Pavel Emelyanov <xemul@parallels.com> writes:

> Eric W. Biederman wrote:
>> Pavel Emelyanov <xemul@parallels.com> writes:
>> 
>>>>> Yet another set of per-namespace IDs along with CLONE_NEWXXX ones?
>>>>> I currently have a way to create all namespaces we have with one
>>>>> syscall. Why don't we have an ability to enter them all with one syscall?
>>>> The CLONE_NEWXXX series of bits has been an royal pain to work with,
>>>> and it appears to be unnecessary complications for no gain.
>>> That's the answer for the "Yet another set..." question.
>>> How about the "Why don't we have..." one?
>> 
>> I am not certain which question you are asking:
>> 
>> Why don't we have an ability to enter all namespaces with one syscall
>> invocation?
>
> Exactly. Please add at least the NSTYPE_NSPROXY or whatever, that will
> pin all namespaces of a given pid from the very beginning.

For nsfd(2) that is doable.  At least for now setns can't restore it.

>> Why don't we have a syscall that allows us to enter every namespace?
>
> This one is done in the patch, no?
>
> Although the approach is OK for me, there's one design issue, that came
> up to my mind recently: can we use this fd to wail for a namespace to 
> stop? I currently don't see this ability, but this is something I require
> badly.

I have designed these file descriptors to pin the namespaces, so
waiting for them to exit isn't something they can do now.  It makes a
lot of sense to have similar ones that take  weak references to the namespaces
that we can use to wait for a namespace to exit.

Eric