tracing: Only allow trace_array_printk() to be used by instances

To prevent default "trace_printks()" from spamming the top level tracing
ring buffer, only allow trace instances to use trace_array_printk() (which
can be used without the trace_printk() start up warning).
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -3346,12 +3346,16 @@ int trace_array_printk(struct trace_array *tr,
 	int ret;
 	va_list ap;
 
-	if (!(global_trace.trace_flags & TRACE_ITER_PRINTK))
-		return 0;
-
 	if (!tr)
 		return -ENOENT;
 
+	/* This is only allowed for created instances */
+	if (tr == &global_trace)
+		return 0;
+
+	if (!(tr->trace_flags & TRACE_ITER_PRINTK))
+		return 0;
+
 	va_start(ap, fmt);
 	ret = trace_array_vprintk(tr, ip, fmt, ap);
 	va_end(ap);