re #13613 rb4516 Tunables needs volatile keyword

*** 18,27 ****
--- 18,28 ----
   *
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
   * Copyright (c) 2015, Joyent, Inc.
   * Copyright (c) 2017 by Delphix. All rights reserved.
   */
  
  /*      Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T     */
*** 142,152 ****
   *
   * the initial value was chosen as being
   * a random string of bits, probably not
   * normally chosen by a systems administrator
   */
! int ncsize = -1;
  volatile uint32_t dnlc_nentries = 0;    /* current num of name cache entries */
  static int nc_hashsz;                   /* size of hash table */
  static int nc_hashmask;                 /* size of hash table minus 1 */
  
  /*
--- 143,153 ----
   *
   * the initial value was chosen as being
   * a random string of bits, probably not
   * normally chosen by a systems administrator
   */
! volatile int ncsize = -1;
  volatile uint32_t dnlc_nentries = 0;    /* current num of name cache entries */
  static int nc_hashsz;                   /* size of hash table */
  static int nc_hashmask;                 /* size of hash table minus 1 */
  
  /*
*** 301,313 ****
   */
  #define DC_RET_LOW_MEM (dircache_t *)1
  #define VALID_DIR_CACHE(dcp) ((dircache_t *)(dcp) > DC_RET_LOW_MEM)
  
  /* Tunables */
! uint_t dnlc_dir_enable = 1; /* disable caching directories by setting to 0 */
! uint_t dnlc_dir_min_size = 40; /* min no of directory entries before caching */
! uint_t dnlc_dir_max_size = UINT_MAX; /* ditto maximum */
  uint_t dnlc_dir_hash_size_shift = 3; /* 8 entries per hash bucket */
  uint_t dnlc_dir_min_reclaim =  350000; /* approx 1MB of dcentrys */
  /*
   * dnlc_dir_hash_resize_shift determines when the hash tables
   * get re-adjusted due to growth or shrinkage
--- 302,316 ----
   */
  #define DC_RET_LOW_MEM (dircache_t *)1
  #define VALID_DIR_CACHE(dcp) ((dircache_t *)(dcp) > DC_RET_LOW_MEM)
  
  /* Tunables */
! volatile uint_t dnlc_dir_enable = 1;    /* disable caching directories by */
!                                         /* setting to 0 */
! volatile uint_t dnlc_dir_min_size = 40; /* min no of directory entries before */
!                                         /* caching */
! volatile uint_t dnlc_dir_max_size = UINT_MAX; /* ditto maximum */
  uint_t dnlc_dir_hash_size_shift = 3; /* 8 entries per hash bucket */
  uint_t dnlc_dir_min_reclaim =  350000; /* approx 1MB of dcentrys */
  /*
   * dnlc_dir_hash_resize_shift determines when the hash tables
   * get re-adjusted due to growth or shrinkage