Currently the kernel uses open code in multiple places to check if a
task is in the root PID namespace with the kind of format:

   if (task_active_pid_ns(current) == &init_pid_ns)
       do_something();

This patch creates a new helper function, task_is_in_init_pid_ns(), it
returns true if a passed task is in the root PID namespace, otherwise
returns false.  So it will be used to replace open codes.

Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Leo Yan <redacted>
---
  include/linux/pid_namespace.h | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 7c7e627503d2..07481bb87d4e 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h

@@ -86,4 +86,9 @@ extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
  void pidhash_init(void);
  void pid_idr_init(void);
  
+static inline bool task_is_in_init_pid_ns(struct task_struct *tsk)
+{
+	return task_active_pid_ns(tsk) == &init_pid_ns;
+}
+