linux-kernel - Re: [PATCH] proc: Add complete process group list

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Message-ID: <20100622160442.GA9072@redhat.com>
Date:	Tue, 22 Jun 2010 18:04:42 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Mike McCormack <mikem@...g3k.org>
Cc:	akpm@...ux-foundation.org, kosaki.motohiro@...fujitsu.com,
	serue@...ibm.com, jmorris@...ei.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: Add complete process group list

On 06/23, Mike McCormack wrote:
>
> The new file /proc/<pid>/groups consists of a single group id per line,
>  with each line being 11 characters long.  This should be enough space
>  for 16bit or 32bit group ids.
>
> This feature might be useful for a server listening on a unix domain pipe
>  to determine the list of groups that a client process is in from its pid.

As usual, I can never comment whether we need this or not. Just a minor
nit about the code,

> +static int groups_proc_show(struct seq_file *m, void *v)
> +{
> +	struct inode *inode = m->private;
> +	struct group_info *group_info;
> +	struct task_struct *task;
> +	const struct cred *cred;
> +	struct pid *pid;
> +	unsigned int g;
> +
> +	pid = proc_pid(inode);
> +	task = get_pid_task(pid, PIDTYPE_PID);

get_proc_task() ?

> +	if (!task)
> +		return -ESRCH;
> +
> +	cred = get_task_cred(task);

OTOH. Not that I think this is terribly important, but I don't think
this needs get_task_struct + get_cred,

	group_info = NULL;

	rcu_read_lock();
	task = pid_task(proc_pid(inode), PIDTYPE_PID);
	if (task) {
		group_info = _task_cred(task)->group_info;
		get_group_info(group_info);
	}
	rcu_read_unlock();

	if (!group_info)
		retrn ESRCH;

Feel free to ignore though.

Oleg.

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