3996 want a libzfs_core API to rollback to latest snapshot
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>

*** 3516,3526 ****
  int
  zfs_rollback(zfs_handle_t *zhp, zfs_handle_t *snap, boolean_t force)
  {
          rollback_data_t cb = { 0 };
          int err;
-         zfs_cmd_t zc = { 0 };
          boolean_t restore_resv = 0;
          uint64_t old_volsize, new_volsize;
          zfs_prop_t resv_prop;
  
          assert(zhp->zfs_type == ZFS_TYPE_FILESYSTEM ||
--- 3516,3525 ----
*** 3548,3573 ****
                  old_volsize = zfs_prop_get_int(zhp, ZFS_PROP_VOLSIZE);
                  restore_resv =
                      (old_volsize == zfs_prop_get_int(zhp, resv_prop));
          }
  
-         (void) strlcpy(zc.zc_name, zhp->zfs_name, sizeof (zc.zc_name));
- 
-         if (ZFS_IS_VOLUME(zhp))
-                 zc.zc_objset_type = DMU_OST_ZVOL;
-         else
-                 zc.zc_objset_type = DMU_OST_ZFS;
- 
          /*
           * We rely on zfs_iter_children() to verify that there are no
           * newer snapshots for the given dataset.  Therefore, we can
           * simply pass the name on to the ioctl() call.  There is still
           * an unlikely race condition where the user has taken a
           * snapshot since we verified that this was the most recent.
-          *
           */
!         if ((err = zfs_ioctl(zhp->zfs_hdl, ZFS_IOC_ROLLBACK, &zc)) != 0) {
                  (void) zfs_standard_error_fmt(zhp->zfs_hdl, errno,
                      dgettext(TEXT_DOMAIN, "cannot rollback '%s'"),
                      zhp->zfs_name);
                  return (err);
          }
--- 3547,3565 ----
                  old_volsize = zfs_prop_get_int(zhp, ZFS_PROP_VOLSIZE);
                  restore_resv =
                      (old_volsize == zfs_prop_get_int(zhp, resv_prop));
          }
  
          /*
           * We rely on zfs_iter_children() to verify that there are no
           * newer snapshots for the given dataset.  Therefore, we can
           * simply pass the name on to the ioctl() call.  There is still
           * an unlikely race condition where the user has taken a
           * snapshot since we verified that this was the most recent.
           */
!         err = lzc_rollback(zhp->zfs_name, NULL, 0);
!         if (err != 0) {
                  (void) zfs_standard_error_fmt(zhp->zfs_hdl, errno,
                      dgettext(TEXT_DOMAIN, "cannot rollback '%s'"),
                      zhp->zfs_name);
                  return (err);
          }