3484 enhance and document tail follow support
Reviewed by: Joshua M. Clulow <jmc@joyent.com>

*** 29,38 ****
--- 29,42 ----
  /*
   *      Copyright 1983,1984,1985,1986,1987,1988,1989 AT&T.
   *      All Rights Reserved
   */
  
+ /*
+  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
+  */
+ 
  #include <sys/param.h>
  #include <sys/types.h>
  #include <sys/systm.h>
  #include <sys/cred.h>
  #include <sys/time.h>
*** 6651,6670 ****
          if (error) {
                  VN_RELE(vp);
          } else {
                  vnode_t *tvp;
                  rnode4_t *trp;
-                 /*
-                  * existing file got truncated, notify.
-                  */
                  tvp = vp;
                  if (vp->v_type == VREG) {
                          trp = VTOR4(vp);
                          if (IS_SHADOW(vp, trp))
                                  tvp = RTOV4(trp);
                  }
                  vnevent_create(tvp, ct);
                  *vpp = vp;
          }
          return (error);
  
  create_otw:
--- 6655,6678 ----
          if (error) {
                  VN_RELE(vp);
          } else {
                  vnode_t *tvp;
                  rnode4_t *trp;
                  tvp = vp;
                  if (vp->v_type == VREG) {
                          trp = VTOR4(vp);
                          if (IS_SHADOW(vp, trp))
                                  tvp = RTOV4(trp);
                  }
+ 
+                 if (must_trunc) {
+                         /*
+                          * existing file got truncated, notify.
+                          */
                          vnevent_create(tvp, ct);
+                 }
+ 
                  *vpp = vp;
          }
          return (error);
  
  create_otw: