[PATCH] /proc/pid/status: show all sets of pid according to ns

[chenhanxiao at cn.fujitsu.com]

> -----Original Message-----
> From: Richard Weinberger [mailto:richard.weinberger at gmail.com]
> Sent: Monday, May 26, 2014 7:10 PM
> To: Chen, Hanxiao/陈 晗霄
> Cc: Linux Containers; LKML; Andrew Morton; Eric W. Biederman; Serge Hallyn;
> Daniel P. Berrange; Oleg Nesterov; Al Viro; David Howells
> Subject: Re: [PATCH] /proc/pid/status: show all sets of pid according to ns
> 
> On Mon, May 26, 2014 at 12:05 PM, Chen Hanxiao
> <chenhanxiao at cn.fujitsu.com> wrote:
> > We need a direct method of getting the pid inside containers.
> > 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 expands fields of Tgid and Pid:
> > a) In init_pid_ns, nothing changed;
> >
> > b) In one pidns, they will tell the pid inside containers:
> > Tgid:   1628    9       3
> > Pid:    1628    9       3
> > ** process id is 1628 in level 0, 9 in level 1, 3 in level 2.
> >
> > c) If pidns is nested, it depends on which pidns are you in.
> > Tgid:   9       3
> > Pid:    9       3
> > ** Views from level 1 for Pid 1628 in host.
> >
> > Signed-off-by: Chen Hanxiao <chenhanxiao at cn.fujitsu.com>
> > ---
> >  fs/proc/array.c | 20 +++++++++++++-------
> >  1 file changed, 13 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/proc/array.c b/fs/proc/array.c
> > index 64db2bc..eef20dd 100644
> > --- a/fs/proc/array.c
> > +++ b/fs/proc/array.c
> > @@ -173,17 +173,23 @@ static inline void task_state(struct seq_file *m, struct
> pid_namespace *ns,
> >         cred = get_task_cred(p);
> >         seq_printf(m,
> >                 "State:\t%s\n"
> > -               "Tgid:\t%d\n"
> > -               "Ngid:\t%d\n"
> > -               "Pid:\t%d\n"
> > +               "Ngid:\t%d\n",
> 
> You're changing the ordering of Tgid and Ngid here.

I just want to put Tgid and Pid together, for showing all sets of pids of them. 

> 
> > +               get_task_state(p),
> > +               task_numa_group_id(p));
> > +       seq_puts(m, "Tgid:");
> > +       for (g = ns->level; g <= pid->level; g++)
> > +               seq_printf(m, "\t%d ",
> > +               task_tgid_nr_ns(p, pid->numbers[g].ns));
> 
> I like the idea but IMHO we should keep Tgid and Pid as is and better
> add two new fields to /proc/pid/status.
> What about NSpid and NSgid?
> 

That's a good idea.
As Vasily's comments,
keeping Pid unchanged would be better for backward compatibility.

> > +       seq_puts(m, "\nPid:");
> > +       for (g = ns->level; g <= pid->level; g++)
> > +               seq_printf(m, "\t%d ",
> > +               task_pid_nr_ns(p, pid->numbers[g].ns));
> > +       seq_putc(m, '\n');
> > +       seq_printf(m,
> >                 "PPid:\t%d\n"
> >                 "TracerPid:\t%d\n"
> >                 "Uid:\t%d\t%d\t%d\t%d\n"
> >                 "Gid:\t%d\t%d\t%d\t%d\n",
> > -               get_task_state(p),
> > -               task_tgid_nr_ns(p, ns),
> > -               task_numa_group_id(p),
> > -               pid_nr_ns(pid, ns),
> >                 ppid, tpid,
> >                 from_kuid_munged(user_ns, cred->uid),
> >                 from_kuid_munged(user_ns, cred->euid),
> > --
> > 1.9.0
> >
> > --
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> 
> 
> 
> --
> Thanks,
> //richard