[PATCH v2] /proc/pid/status: show all sets of pid according to ns

[Chen Hanxiao]

We need a direct 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 adds two fields:

NStgid and NSpid.

a) In init_pid_ns, nothing changed;

b) In one pidns, will tell the pid inside containers:
NStgid:	1628 	9 	3
NSpid:	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.
NStgid:	9 	3
NSpid:	9 	3
** Views from level 1

Signed-off-by: Chen Hanxiao <chenhanxiao@xxxxxxxxxxxxxx>
---
v2: add two new fields: NStgid and NSpid.
    keep fields of Tgid and Pid unchanged for back compatibility.

 fs/proc/array.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 64db2bc..9b7e65c 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -193,6 +193,15 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
 		from_kgid_munged(user_ns, cred->egid),
 		from_kgid_munged(user_ns, cred->sgid),
 		from_kgid_munged(user_ns, cred->fsgid));
+	seq_puts(m, "NStgid:");
+	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_putc(m, '\n');
 
 	task_lock(p);
 	if (p->files)
-- 
1.9.0

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