tracefs: Annotate tracefs_ops with __ro_after_init

tracefs_ops is initialized inside tracefs_create_instance_dir and not
modified after. tracefs_create_instance_dir allows for initialization
only once, and is called from create_trace_instances(marked __init),
which is called from tracer_init_tracefs(marked __init). Also, mark
tracefs_create_instance_dir as __init.

Link: http://lkml.kernel.org/r/20180725171901.4468-1-zsm@chromium.org

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fs/tracefs/inode.c

@@ -53,7 +53,7 @@ static const struct file_operations tracefs_file_operations = {
 static struct tracefs_dir_ops {
 	int (*mkdir)(const char *name);
 	int (*rmdir)(const char *name);
-} tracefs_ops;
+} tracefs_ops __ro_after_init;
 
 static char *get_dname(struct dentry *dentry)
 {
@@ -478,7 +478,8 @@ struct dentry *tracefs_create_dir(const char *name, struct dentry *parent)
  *
  * Returns the dentry of the instances directory.
  */
-struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
+__init struct dentry *tracefs_create_instance_dir(const char *name,
+					  struct dentry *parent,
 					  int (*mkdir)(const char *name),
 					  int (*rmdir)(const char *name))
 {