tracing: Fix initial buffer_size_kb state

Make sure that the state of buffer_size_kb is initialized correctly and
returns actual size of the ring buffer.

Link: http://lkml.kernel.org/r/1336066834-1673-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Laurent Chavey <chavey@google.com>
Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -5112,7 +5112,8 @@ __init static int tracer_alloc_buffers(void)
 		max_tr.data[i] = &per_cpu(max_tr_data, i);
 	}
 
-	set_buffer_entries(&global_trace, ring_buf_size);
+	set_buffer_entries(&global_trace,
+			   ring_buffer_size(global_trace.buffer, 0));
 #ifdef CONFIG_TRACER_MAX_TRACE
 	set_buffer_entries(&max_tr, 1);
 #endif