locking/atomic, kref: Add kref_read()

Since we need to change the implementation, stop exposing internals.

Provide kref_read() to read the current reference count; typically
used for debug messages.

Kills two anti-patterns:

	atomic_read(&kref->refcount)
	kref->refcount.counter

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/net/bluetooth/amp.c b/net/bluetooth/amp.c
index e32f341..02a4ccc 100644
--- a/net/bluetooth/amp.c
+++ b/net/bluetooth/amp.c
@@ -24,7 +24,7 @@
 void amp_ctrl_get(struct amp_ctrl *ctrl)
 {
 	BT_DBG("ctrl %p orig refcnt %d", ctrl,
-	       atomic_read(&ctrl->kref.refcount));
+	       kref_read(&ctrl->kref));
 
 	kref_get(&ctrl->kref);
 }
@@ -42,7 +42,7 @@
 int amp_ctrl_put(struct amp_ctrl *ctrl)
 {
 	BT_DBG("ctrl %p orig refcnt %d", ctrl,
-	       atomic_read(&ctrl->kref.refcount));
+	       kref_read(&ctrl->kref));
 
 	return kref_put(&ctrl->kref, &amp_ctrl_destroy);
 }