linux-kernel - Re: [Resend][PATCH] ns,proc: introduce pid_in

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Message-ID: <20140425185645.GA10637@redhat.com>
Date:	Fri, 25 Apr 2014 20:56:45 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Chen Hanxiao <chenhanxiao@...fujitsu.com>
Cc:	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	"Daniel P. Berrange" <berrange@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Howells <dhowells@...hat.com>
Subject: Re: [Resend][PATCH] ns,proc: introduce pid_in_ns

On 04/25, Chen Hanxiao wrote:
>
> We lacked of convenient method of getting the pid inside containers.
>
> If some issues occurred inside 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 introduces pid_in_ns:
> If one process is in init_pid_ns, /proc/PID/pid_in_ns
> equals to /proc/PID;
> if one process is in pidns, /proc/PID/pid_in_ns
> will tell the pid inside containers;
> if pidns is nested, it depends on which pidns are you in.

Yes another /proc/pid/ file...

Perhaps it would be better to change /proc/pid/status["Pid:"] to report the
list of pid_nr's, from its namespace up to the observer's namespace. The same
for "Tgid:".

(Hmm. And why "Ngid:" was inserted between tid and tgid ?)

> +int proc_pid_in_ns(struct seq_file *m, struct pid_namespace *ns,
> +			struct pid *pid, struct task_struct *task)
> +{
> +	pid_t pid_in_ns;
> +	unsigned int level;
> +
> +	level = pid->level;
> +	pid_in_ns = task_pid_nr_ns(task, pid->numbers[level].ns);

This looks overcomplicated or I missed something?

Oleg.

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