Re: How much of a mess does OpenVZ make? ;) Was: What can OpenVZ do?

Serge E. Hallyn wrote:

Quoting Cedric Le Goater (legoater@free.fr):

quoted

quoted

No, what you're suggesting does not suffice.

probably. I'm still trying to understand what you mean below :)

Man, I hate these hierarchicals pid_ns. one level would have been enough, 
just one vpid attribute in 'struct pid*'

Well I don't mind - temporarily - saying that nested pid namespaces
are not checkpointable.  It's just that if we're going to need a new
syscall anyway, then why not go ahead and address the whole problem?
It's not hugely more complicated, and seems worth it.

yes. agree. there's a thread going on that topic. i'm following it.

[ ... ] 

quoted

anyway, I think that some CLONE_NEW* should be forbidden. Daniel should
send soon a little patch for the ns_cgroup restricting the clone flags
being used in a container.

Uh, that feels a bit over the top.  We want to make this
uncheckpointable (if it remains so), not prevent the whole action.
After all I may be running a container which I don't plan on ever
checkpointing, and inside that container running a job which i do
want to migrate.

ok. i've been scanning the emails a bit fast. that would be fine 
and useful.

So depending on if we're doing the Dave or the rest-of-the-world
way :), we either clear_bit(pidns->may_checkpoint) on the parent
pid_ns when a child is created, or we walk every task being
checkpointed and make sure they each are in the same pid_ns.  
Doesn't that suffice?

yes. this 'may_checkpoint' is a container level info so I wonder 
where you store it. in a cgroup_checkpoint ? sorry for jumping in 
and may be restarting some old topics of discussion.

C.

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