ptrace: s/tracehook_tracer_task()/ptrace_parent()/

tracehook.h is on the way out.  Rename tracehook_tracer_task() to
ptrace_parent() and move it from tracehook.h to ptrace.h.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: John Johansen <john.johansen@canonical.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index b546fd6..bb157bd 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -151,6 +151,24 @@
 			    unsigned long data);
 
 /**
+ * ptrace_parent - return the task that is tracing the given task
+ * @task: task to consider
+ *
+ * Returns %NULL if no one is tracing @task, or the &struct task_struct
+ * pointer to its tracer.
+ *
+ * Must called under rcu_read_lock().  The pointer returned might be kept
+ * live only by RCU.  During exec, this may be called with task_lock() held
+ * on @task, still held from when check_unsafe_exec() was called.
+ */
+static inline struct task_struct *ptrace_parent(struct task_struct *task)
+{
+	if (unlikely(task->ptrace))
+		return rcu_dereference(task->parent);
+	return NULL;
+}
+
+/**
  * ptrace_event_enabled - test whether a ptrace event is enabled
  * @task: ptracee of interest
  * @event: %PTRACE_EVENT_* to test
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index bcc4ca7..7a1bd12 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -130,24 +130,6 @@
 }
 
 /**
- * tracehook_tracer_task - return the task that is tracing the given task
- * @tsk:		task to consider
- *
- * Returns NULL if no one is tracing @task, or the &struct task_struct
- * pointer to its tracer.
- *
- * Must called under rcu_read_lock().  The pointer returned might be kept
- * live only by RCU.  During exec, this may be called with task_lock()
- * held on @task, still held from when tracehook_unsafe_exec() was called.
- */
-static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk)
-{
-	if (tsk->ptrace & PT_PTRACED)
-		return rcu_dereference(tsk->parent);
-	return NULL;
-}
-
-/**
  * tracehook_signal_handler - signal handler setup is complete
  * @sig:		number of signal being delivered
  * @info:		siginfo_t of signal being delivered