[PATCH] [RFC] c/r: Add UTS support
daniel.lezcano at free.fr
Fri Mar 13 08:51:56 PDT 2009
Serge E. Hallyn wrote:
> Quoting Daniel Lezcano (daniel.lezcano at free.fr):
>> Dan Smith wrote:
>>> DL> I guess it will be esay to implement with a nsproxy level counter.
>>> DL> Each time you unshare, the new nsproxy count is incremented.
>>> DL> Assuming the init_nsproxy is level 0, when the nsproxy counter is
>>> DL> > 1, the process is uncheckpointable.
>>> This should also be possible by just making sure that the nsproxy of
>>> the root process being checkpointed is the same as any of the
>>> children, correct? That way we avoid having to modify the core
>>> nsproxy bits and can still reject any nested namespaces.
>> Right, this is another option. The nsproxy counter will allow to flag at
>> runtime a process to be uncheckpointable. The nsproxy comparison will
>> detect nested nsproxies at checkpoint time.
> Or, to stick more to the resource->may_checkpoint way of doing it, you
> setbit(&nsproxy->uts_ns->may_checkpoint, 0) when the uts_ns is
> created, and anytime a task does clone(CLONE_NEWUTS) or
> unshare(CLONE_NEWUTS), you clear the bit on the parent uts_ns.
Hmm, you will need to add a back pointer for the nsproxy | utsns parent,
What I was proposing is a counter directly in the nsproxy. Maybe instead
of initializing it to zero, it can be initialized to the max supported
nested level ( only one right now) and decrement each time a clone or a
unshare is done whatever the namespace.
init nsproxy->may_checkpoint = 2
First clone | unshare => for the new nsproxy the counter may_checkpoint
Second clone | unshare (forbidden) => may_checkpoint becomes 0
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