[PATCH v10 1/2] /proc/PID/status: show all sets of pid according to ns

[Andrew Morton]

On Fri, 6 Feb 2015 18:45:49 +0800 Chen Hanxiao <chenhanxiao at cn.fujitsu.com> wrote:

> If some issues occurred inside a container guest, host user
> could not know which process is in trouble just by guest pid:
> the users of container guest only knew the pid inside containers.
> This will bring obstacle for trouble shooting.
> 
> This patch adds four fields: NStgid, NSpid, NSpgid and NSsid:
> a) In init_pid_ns, nothing changed;
> 
> b) In one pidns, will tell the pid inside containers:
>   NStgid: 21776   5       1
>   NSpid:  21776   5       1
>   NSpgid: 21776   5       1
>   NSsid:  21729   1       0
>   ** Process id is 21776 in level 0, 5 in level 1, 1 in level 2.
> 
> c) If pidns is nested, it depends on which pidns are you in.
>   NStgid: 5       1
>   NSpid:  5       1
>   NSpgid: 5       1
>   NSsid:  1       0
>   ** Views from level 1
> 
> ...
>
> --- a/fs/proc/array.c
> +++ b/fs/proc/array.c
> @@ -208,6 +208,22 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
>  			   from_kgid_munged(user_ns, GROUP_AT(group_info, g)));
>  	put_cred(cred);
>  
> +	seq_puts(m, "\nNStgid:");
> +	for (g = ns->level; g <= pid->level; g++)
> +		seq_printf(m, "\t%d",
> +			task_tgid_nr_ns(p, pid->numbers[g].ns));
> +	seq_puts(m, "\nNSpid:");
> +	for (g = ns->level; g <= pid->level; g++)
> +		seq_printf(m, "\t%d",
> +			task_pid_nr_ns(p, pid->numbers[g].ns));
> +	seq_puts(m, "\nNSpgid:");
> +	for (g = ns->level; g <= pid->level; g++)
> +		seq_printf(m, "\t%d",
> +			task_pgrp_nr_ns(p, pid->numbers[g].ns));
> +	seq_puts(m, "\nNSsid:");
> +	for (g = ns->level; g <= pid->level; g++)
> +		seq_printf(m, "\t%d",
> +			task_session_nr_ns(p, pid->numbers[g].ns));
>  	seq_putc(m, '\n');
>  }

Is there any point in including this code if CONFIG_USER_NS=n?