[PATCH 1/2] Revert "pid: make __task_pid_nr_ns(ns => NULL) safe for zombie callers"

[Oleg Nesterov <oleg@redhat.com>]

This reverts commit abdfd4948e45c51b19162cf8b3f5003f8f53c9b9.

The changelog in this commit explains why it is not easy to avoid ns == NULL
when the caller is exiting, but pid_vnr() is equally unsafe in this case.

However, commit 006568ab4c5c ("pid: Add a judgment for ns null in pid_nr_ns")
already added the ns != NULL check in pid_nr_ns(), so we can remove the same
check from __task_pid_nr_ns().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/pid.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index 4fffec767a63..be69ae771e3c 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -515,8 +515,7 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
 	rcu_read_lock();
 	if (!ns)
 		ns = task_active_pid_ns(current);
-	if (ns)
-		nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
+	nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
 	rcu_read_unlock();
 
 	return nr;
-- 
2.25.1.362.g51ebf55