[Devel] Re: [PATCH 7/15] Helpers to obtain pid numbers

[Oleg Nesterov]

On 07/26, Pavel Emelyanov wrote:
>
> --- linux-2.6.23-rc1-mm1.orig/include/linux/pid.h	2007-07-26 16:34:45.000000000 +0400
> +++ linux-2.6.23-rc1-mm1-7/include/linux/pid.h	2007-07-26 16:36:37.000000000 +0400
> @@ -83,12 +92,34 @@ extern void FASTCALL(detach_pid(struct t
>
>  extern struct pid *alloc_pid(struct pid_namespace *ns);
>  extern void FASTCALL(free_pid(struct pid *pid));
> +
> +/*
> + * the helpers to get the pid's id seen from different namespaces
> + *
> + * pid_nr()    : global id, i.e. the id seen from the init namespace;

This looks a bit strange to me, but perhaps this is just matter of taste.
I think pid_nr(pid) should be pid_nr_ns(pid, current->nsproxy->pid_ns),
this is imho much closer to the current meaning. I won't persist though.

> +pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
> +{
> +	pid_t nr = 0;
> +	if (pid && ns->level <= pid->level)
> +		nr = pid->numbers[ns->level].nr;
> +	return nr;
> +}

I am not sure I understand the "ns->level <= pid->level" check. Isn't it
a bug to use a "wrong" namespace here? In that case BUG_ON() looks better.

If ns could be wrong, "ns->level <= pid->level" is not enough, we should
also check "pid->numbers[ns->level].ns == ns", no?

Oleg.