8264 want support for promoting datasets in libzfs_core

*** 29,38 ****
--- 29,39 ----
   * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
   * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
   * Copyright (c) 2013 Steven Hartland. All rights reserved.
   * Copyright (c) 2014 Integros [integros.com]
   * Copyright 2016 Toomas Soome <tsoome@me.com>
+  * Copyright 2017 RackTop Systems.
   */
  
  /*
   * ZFS ioctls.
   *
*** 4700,4727 ****
          return (0);
  }
  /*
   * inputs:
   * zc_name      name of filesystem
-  * zc_value     name of origin snapshot
   *
   * outputs:
   * zc_string    name of conflicting snapshot, if there is one
   */
  static int
  zfs_ioc_promote(zfs_cmd_t *zc)
  {
          char *cp;
  
          /*
           * We don't need to unmount *all* the origin fs's snapshots, but
           * it's easier.
           */
!         cp = strchr(zc->zc_value, '@');
          if (cp)
                  *cp = '\0';
!         (void) dmu_objset_find(zc->zc_value,
              zfs_unmount_snap_cb, NULL, DS_FIND_SNAPSHOTS);
          return (dsl_dataset_promote(zc->zc_name, zc->zc_string));
  }
  
  /*
--- 4701,4760 ----
          return (0);
  }
  /*
   * inputs:
   * zc_name      name of filesystem
   *
   * outputs:
   * zc_string    name of conflicting snapshot, if there is one
   */
  static int
  zfs_ioc_promote(zfs_cmd_t *zc)
  {
+         dsl_pool_t *dp;
+         dsl_dataset_t *ds, *ods;
+         char origin[ZFS_MAX_DATASET_NAME_LEN];
          char *cp;
+         int error;
  
+         error = dsl_pool_hold(zc->zc_name, FTAG, &dp);
+         if (error != 0)
+                 return (error);
+ 
+         error = dsl_dataset_hold(dp, zc->zc_name, FTAG, &ds);
+         if (error != 0) {
+                 dsl_pool_rele(dp, FTAG);
+                 return (error);
+         }
+ 
+         if (!dsl_dir_is_clone(ds->ds_dir)) {
+                 dsl_dataset_rele(ds, FTAG);
+                 dsl_pool_rele(dp, FTAG);
+                 return (SET_ERROR(EINVAL));
+         }
+ 
+         error = dsl_dataset_hold_obj(dp,
+             dsl_dir_phys(ds->ds_dir)->dd_origin_obj, FTAG, &ods);
+         if (error != 0) {
+                 dsl_dataset_rele(ds, FTAG);
+                 dsl_pool_rele(dp, FTAG);
+                 return (error);
+         }
+ 
+         dsl_dataset_name(ods, origin);
+         dsl_dataset_rele(ods, FTAG);
+         dsl_dataset_rele(ds, FTAG);
+         dsl_pool_rele(dp, FTAG);
+ 
          /*
           * We don't need to unmount *all* the origin fs's snapshots, but
           * it's easier.
           */
!         cp = strchr(origin, '@');
          if (cp)
                  *cp = '\0';
!         (void) dmu_objset_find(origin,
              zfs_unmount_snap_cb, NULL, DS_FIND_SNAPSHOTS);
          return (dsl_dataset_promote(zc->zc_name, zc->zc_string));
  }
  
  /*