5819 want dumpadm(1m) option to print estimated dump size

*** 18,27 ****
--- 18,28 ----
   *
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.
+  * Copyright 2015 Nexenta Systems, Inc. All rights reserved.
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/swap.h>
*** 517,526 ****
--- 518,544 ----
                  warn(gettext("kernel image uuid write failed"));
  
          return (err == 0);
  }
  
+ int
+ dconf_get_dumpsize(dumpconf_t *dcp)
+ {
+         char buf[32];
+         uint64_t d;
+ 
+         if (ioctl(dcp->dc_dump_fd, DIOCGETDUMPSIZE, &d) == -1) {
+                 warn(gettext("failed to get kernel dump size"));
+                 return (-1);
+         }
+ 
+         zfs_nicenum(d, buf, sizeof (buf));
+ 
+         (void) printf(gettext("Estimated dump size: %s\n"), buf);
+         return (0);
+ }
+ 
  void
  dconf_print(dumpconf_t *dcp, FILE *fp)
  {
          u_longlong_t min;
          char *content;