[resend][PATCH v9 2/3] /proc/PID/status: show all sets of pid according to ns

[Chen Hanxiao]

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

Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
Tested-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>

Signed-off-by: Chen Hanxiao <chenhanxiao@xxxxxxxxxxxxxx>
---
v9: rebased on 3.19-rc1
No change from v4-v8
v3: add another two fielsd: NSpgid and NSsid.
v2: add two new fields: NStgid and NSpid.
    keep fields of Tgid and Pid unchanged for back compatibility.

 fs/proc/array.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index bd117d0..35205d4 100644
--- 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');
 }
 
-- 
1.9.3

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