[Devel] [PATCH VZ10 v2 3/3] ve_namespace: Allow entering non-running VE namespace

[Vasileios Almpanis]

> This doesn't bring a lot of value and makes tests more complex.
> To enter VE namespace we need to actually start VE.
> 
> In vzctl we have locking to prevent parallel creations.
> If someone decides to skip locks and start one CT
> in parallel - big mistake, but not ours.
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-144504
> 
> Feature: ve selftests
> Signed-off-by: Vladimir Riabchun <vladimir.riabchun at virtuozzo.com>
>
> diff --git a/kernel/ve/ve_namespace.c b/kernel/ve/ve_namespace.c
> index 3dbe0dde2645..879a7863e33f 100644
> --- a/kernel/ve/ve_namespace.c
> +++ b/kernel/ve/ve_namespace.c
> @@ -227,7 +227,8 @@ static int ve_ns_install(struct nsset *nsset, struct ns_common *new)
>  		return -EPERM;
>  
>  	if (!VE_IS_RUNNING(ve_ns->ve))
> -		return -EINVAL;
> +		pr_warn_once("Switching to a non-running ve %s.\n",

Maybe better print ve->veid instead of ve_name(). ve_offline() sets
ve->ve_name to NULL when the ve cgroup is removed, so we will see 
"ve (null)" in that case.

> +			ve_name(ve_ns->ve));

This change means that now a host task can enter the CT before the CT
has been started. A task can enter into the VE by two ways either
copy_ve_ns or by switch_ve_namespace both of which call ve_setup_task.
This function sets whether the task can be ptraced, core dumped etc
which will be skipped because ve_setup_task checks if ve is running
which it will not be. So here we break the invariant that tasks that
enter into the ve from host cannot be ptraced etc. I suggest to add
a flag to ve_setup_task entered which will be 1 for switch_ve_namespace
and 0 for copy_ve_ns

-- 
Vasileios Almpanis <vasileios.almpanis at virtuozzo.com>