4171 clean up spa_feature_*() interfaces
4172 implement extensible_dataset feature for use by other zpool features
Reviewed by: Max Grossman <max.grossman@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>

*** 21,31 ****
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
  /*
!  * Copyright (c) 2012 by Delphix. All rights reserved.
   * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
   */
  
  /*
   * The zfs plug-in routines for GRUB are:
--- 21,31 ----
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
  /*
!  * Copyright (c) 2013 by Delphix. All rights reserved.
   * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
   */
  
  /*
   * The zfs plug-in routines for GRUB are:
*** 964,973 ****
--- 964,974 ----
   * When this list is updated the version number in usr/src/grub/capability
   * must be incremented to ensure the new grub gets installed.
   */
  static const char *spa_feature_names[] = {
          "org.illumos:lz4_compress",
+         "com.delphix:extensible_dataset",
          NULL
  };
  
  /*
   * Checks whether the MOS features that are active are supported by this
*** 1042,1052 ****
  
          if (errnum = zap_lookup(mdn, DMU_POOL_ROOT_DATASET, &objnum,
              stack))
                  return (errnum);
  
!         if (errnum = dnode_get(mosmdn, objnum, DMU_OT_DSL_DIR, mdn, stack))
                  return (errnum);
  
          if (fsname == NULL) {
                  headobj =
                      ((dsl_dir_phys_t *)DN_BONUS(mdn))->dd_head_dataset_obj;
--- 1043,1053 ----
  
          if (errnum = zap_lookup(mdn, DMU_POOL_ROOT_DATASET, &objnum,
              stack))
                  return (errnum);
  
!         if (errnum = dnode_get(mosmdn, objnum, 0, mdn, stack))
                  return (errnum);
  
          if (fsname == NULL) {
                  headobj =
                      ((dsl_dir_phys_t *)DN_BONUS(mdn))->dd_head_dataset_obj;
*** 1084,1094 ****
                          return (errnum);
  
                  if (zap_lookup(mdn, cname, &objnum, stack))
                          return (ERR_FILESYSTEM_NOT_FOUND);
  
!                 if (errnum = dnode_get(mosmdn, objnum, DMU_OT_DSL_DIR,
                      mdn, stack))
                          return (errnum);
  
                  *fsname = ch;
                  if (issnapshot)
--- 1085,1095 ----
                          return (errnum);
  
                  if (zap_lookup(mdn, cname, &objnum, stack))
                          return (ERR_FILESYSTEM_NOT_FOUND);
  
!                 if (errnum = dnode_get(mosmdn, objnum, 0,
                      mdn, stack))
                          return (errnum);
  
                  *fsname = ch;
                  if (issnapshot)
*** 1097,1107 ****
          headobj = ((dsl_dir_phys_t *)DN_BONUS(mdn))->dd_head_dataset_obj;
          if (obj)
                  *obj = headobj;
  
  skip:
!         if (errnum = dnode_get(mosmdn, headobj, DMU_OT_DSL_DATASET, mdn, stack))
                  return (errnum);
          if (issnapshot) {
                  uint64_t snapobj;
  
                  snapobj = ((dsl_dataset_phys_t *)DN_BONUS(mdn))->
--- 1098,1108 ----
          headobj = ((dsl_dir_phys_t *)DN_BONUS(mdn))->dd_head_dataset_obj;
          if (obj)
                  *obj = headobj;
  
  skip:
!         if (errnum = dnode_get(mosmdn, headobj, 0, mdn, stack))
                  return (errnum);
          if (issnapshot) {
                  uint64_t snapobj;
  
                  snapobj = ((dsl_dataset_phys_t *)DN_BONUS(mdn))->
*** 1110,1121 ****
                  if (errnum = dnode_get(mosmdn, snapobj,
                      DMU_OT_DSL_DS_SNAP_MAP, mdn, stack))
                          return (errnum);
                  if (zap_lookup(mdn, snapname + 1, &headobj, stack))
                          return (ERR_FILESYSTEM_NOT_FOUND);
!                 if (errnum = dnode_get(mosmdn, headobj,
!                     DMU_OT_DSL_DATASET, mdn, stack))
                          return (errnum);
                  if (obj)
                          *obj = headobj;
          }
  
--- 1111,1121 ----
                  if (errnum = dnode_get(mosmdn, snapobj,
                      DMU_OT_DSL_DS_SNAP_MAP, mdn, stack))
                          return (errnum);
                  if (zap_lookup(mdn, snapname + 1, &headobj, stack))
                          return (ERR_FILESYSTEM_NOT_FOUND);
!                 if (errnum = dnode_get(mosmdn, headobj, 0, mdn, stack))
                          return (errnum);
                  if (obj)
                          *obj = headobj;
          }