OS-881 To workaround OS-580 add support to only invalidate mappings from a single process

*** 19,28 ****
--- 19,29 ----
   * CDDL HEADER END
   */
  /*
   * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
+  * Copyright 2012 Joyent, Inc.  All rights reserved.
   */
  
  /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  /*        All Rights Reserved   */
  
*** 184,193 ****
--- 185,195 ----
  #define B_RETRYWRI      0x400000        /* retry write til works or bfinval */
  #define B_FAILFAST      0x1000000       /* Fail promptly if device goes away */
  #define B_STARTED       0x2000000       /* io:::start probe called for buf */
  #define B_ABRWRITE      0x4000000       /* Application based recovery active */
  #define B_PAGE_NOWAIT   0x8000000       /* Skip the page if it is locked */
+ #define B_INVALCURONLY  0x10000000      /* invalidate only for curproc */
  
  /*
   * There is some confusion over the meaning of B_FREE and B_INVAL and what
   * the use of one over the other implies.
   *
*** 196,205 ****
--- 198,213 ----
   * In the case of B_INVAL, the page will be destroyed (hashed out of it's
   * vnode) and placed on the freelist.  Beyond this, there is no difference
   * between the sole use of these two flags.  In both cases, IO will be done
   * if the page is not yet committed to storage.
   *
+  * The B_INVALCURONLY flag modifies the behavior of the B_INVAL flag and is
+  * intended to be used in conjunction with B_INVAL.  B_INVALCURONLY has no
+  * meaning on its own.  When both B_INVALCURONLY and B_INVAL are set, then
+  * the mapping for the page is only invalidated for the current process.
+  * In this case, the page is not destroyed unless this was the final mapping.
+  *
   * In order to discard pages without writing them back, (B_INVAL | B_TRUNC)
   * should be used.
   *
   * Use (B_INVAL | B_FORCE) to force the page to be destroyed even if we
   * could not successfuly write out the page.