re #13613 rb4516 Tunables needs volatile keyword

*** 21,30 ****
--- 21,31 ----
  /*
   * Copyright 2007 Sun Microsystems, Inc.
   * All rights reserved.  Use is subject to license terms.
   */
  /*
+  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
   * Copyright 2015 Joyent, Inc.
   */
  
  #ifndef _SYS_FS_TMP_H
  #define _SYS_FS_TMP_H
*** 77,87 ****
   * NB: If tmpfs allocates too much swap space, other processes will be
   * unable to execute.
   */
  #define TMPMINFREE      2 * 1024 * 1024 /* 2 Megabytes */
  
! extern size_t   tmpfs_minfree;          /* Anonymous memory in pages */
  
  /*
   * tmpfs can allocate only a certain percentage of kernel memory,
   * which is used for tmpnodes, directories, file names, etc.
   * This is statically set as TMPMAXFRACKMEM of physical memory.
--- 78,88 ----
   * NB: If tmpfs allocates too much swap space, other processes will be
   * unable to execute.
   */
  #define TMPMINFREE      2 * 1024 * 1024 /* 2 Megabytes */
  
! extern volatile size_t  tmpfs_minfree;  /* Anonymous memory in pages */
  
  /*
   * tmpfs can allocate only a certain percentage of kernel memory,
   * which is used for tmpnodes, directories, file names, etc.
   * This is statically set as TMPMAXFRACKMEM of physical memory.
*** 88,98 ****
   * The actual number of allocatable bytes can be patched in tmpfs_maxkmem.
   */
  #define TMPMAXFRACKMEM  25      /* 1/25 of physical memory */
  
  extern size_t   tmp_kmemspace;
! extern size_t   tmpfs_maxkmem;  /* Allocatable kernel memory in bytes */
  
  extern  void    tmpnode_init(struct tmount *, struct tmpnode *,
          struct vattr *, struct cred *);
  extern  int     tmpnode_trunc(struct tmount *, struct tmpnode *, ulong_t);
  extern  void    tmpnode_growmap(struct tmpnode *, ulong_t);
--- 89,99 ----
   * The actual number of allocatable bytes can be patched in tmpfs_maxkmem.
   */
  #define TMPMAXFRACKMEM  25      /* 1/25 of physical memory */
  
  extern size_t   tmp_kmemspace;
! extern volatile size_t  tmpfs_maxkmem;  /* Allocatable kernel memory in bytes */
  
  extern  void    tmpnode_init(struct tmount *, struct tmpnode *,
          struct vattr *, struct cred *);
  extern  int     tmpnode_trunc(struct tmount *, struct tmpnode *, ulong_t);
  extern  void    tmpnode_growmap(struct tmpnode *, ulong_t);