re #13613 rb4516 Tunables needs volatile keyword

*** 23,32 ****
--- 23,35 ----
   * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   * Copyright 2016 Nexenta Systems, Inc.
   * Copyright (c) 2017 by Delphix. All rights reserved.
   */
+ /*
+  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
+  */
  
  /*      Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T     */
  /*        All Rights Reserved   */
  
  /*
*** 812,822 ****
          struct vnode *rvp = NULL;
          int flags = 0;
          kmutex_t *ihm;
          int elapsed;
          int status;
-         extern  int     maxphys;
  
          if (args_len == sizeof (struct ufs_args) && raw_argsp)
                  flags = ((struct ufs_args *)raw_argsp)->flags;
  
          ASSERT(vfs_lock_held(vfsp));
--- 815,824 ----