function-graph: Fix seqfile memory leak

Every time we cat set_graph_function, we leak memory allocated
by seq_open().
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A67D907.2010500@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -2595,6 +2595,14 @@ ftrace_graph_open(struct inode *inode, struct file *file)
 	return ret;
 }
 
+static int
+ftrace_graph_release(struct inode *inode, struct file *file)
+{
+	if (file->f_mode & FMODE_READ)
+		seq_release(inode, file);
+	return 0;
+}
+
 static int
 ftrace_set_func(unsigned long *array, int *idx, char *buffer)
 {
@@ -2724,9 +2732,10 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
 }
 
 static const struct file_operations ftrace_graph_fops = {
-	.open = ftrace_graph_open,
-	.read = seq_read,
-	.write = ftrace_graph_write,
+	.open		= ftrace_graph_open,
+	.read		= seq_read,
+	.write		= ftrace_graph_write,
+	.release	= ftrace_graph_release,
 };
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */