linux-kernel - Re: [patch 1/4] fs, proc: Introduce /proc/<pid>/task/<tid>/children entry v8

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Message-ID: <CAGXu5jJ5yO0oBLo3UJQJeGse7m-oO3MJUyOJCbsCrKXVmXOmmQ@mail.gmail.com>
Date:	Mon, 23 Jan 2012 12:29:52 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>, Andrew Vagin <avagin@...nvz.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [patch 1/4] fs, proc: Introduce /proc/<pid>/task/<tid>/children
 entry v8

On Mon, Jan 23, 2012 at 11:33 AM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
> On Mon, Jan 23, 2012 at 10:54:53AM -0800, Kees Cook wrote:
>> On Mon, Jan 23, 2012 at 6:20 AM, Cyrill Gorcunov <gorcunov@...nvz.org> wrote:
>> > When we do checkpoint of a task we need to know the list of children
>> > the task, has but there is no easy and fast way to generate reverse
>> > parent->children chain from arbitrary <pid> (while a parent pid is
>> > provided in "PPid" field of /proc/<pid>/status).
>> > [...]
>> > Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
>> > Reviewed-by: Oleg Nesterov <oleg@...hat.com>
>> > Cc: Andrew Morton <akpm@...ux-foundation.org>
>> > Cc: Pavel Emelyanov <xemul@...allels.com>
>> > Cc: Serge Hallyn <serge.hallyn@...onical.com>
>> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>
>> Reviewed-by: Kees Cook <keescook@...omium.org>
>>
>> > +static int children_seq_show(struct seq_file *seq, void *v)
>> > +{
>> > +       struct inode *inode = seq->private;
>> > +       pid_t pid;
>> > +
>> > +       pid = pid_nr_ns(v, inode->i_sb->s_fs_info);
>> > +       return seq_printf(seq, " %d", pid);
>> > +}
>>
>> Does this mean the file contents always starts with a space? I think
>> I'd prefer a trailing space than a leading one. Better yet, neither.
>> :)
>>
>
> Yeah, it there children, they will be in say " 1 2 3 4\n" format.
> To drop this space completely i'll have to add more code, which I
> actually trying to escape. Can we live with it? ;)

How about just:

return seq_printf(seq, "%d ", pid);

instead?

-Kees

-- 
Kees Cook
ChromeOS Security
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