[PATCH RFC 3/8] pidns: introduce pidns_get_inum()

[Aristeu Rozanski <arozansk@redhat.com>]

This allows other parts of the kernel to have access to userspace
visible namespace identification.

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>
---
 include/linux/pid_namespace.h |    1 +
 kernel/pid_namespace.c        |   11 +++++++++++
 2 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 215e5e3..8223654 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -57,6 +57,7 @@ extern struct pid_namespace *copy_pid_ns(unsigned long flags,
 extern void zap_pid_ns_processes(struct pid_namespace *pid_ns);
 extern int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd);
 extern void put_pid_ns(struct pid_namespace *ns);
+extern unsigned int pidns_get_inum(struct task_struct *tsk);
 
 #else /* !CONFIG_PID_NS */
 #include <linux/err.h>
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index c1c3dc1..5e463ff 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -361,6 +361,17 @@ static unsigned int pidns_inum(void *ns)
 	return pid_ns->proc_inum;
 }
 
+unsigned int pidns_get_inum(struct task_struct *tsk)
+{
+	unsigned int rc;
+
+	rcu_read_lock();
+	rc = pidns_inum(task_active_pid_ns(tsk));
+	rcu_read_unlock();
+
+	return rc;
+}
+
 const struct proc_ns_operations pidns_operations = {
 	.name		= "pid",
 	.type		= CLONE_NEWPID,
-- 
1.7.1