/proc/PID/status: show all sets of pid according to ns

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

[akpm@linux-foundation.org: add CONFIG_PID_NS ifdef]
Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Tested-by: Serge Hallyn <serge.hallyn@canonical.com>
Tested-by: Nathan Scott <nathans@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 1295a00ca316..a4490c0a4644 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -188,6 +188,24 @@ 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);
 
+#ifdef CONFIG_PID_NS
+        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));
+#endif
         seq_putc(m, '\n');
 }