3973 zfs_ioc_rename alters passed in zc->zc_name
Reviewed by: Matthew Ahrens <mahrens@delphix.com>

*** 3550,3571 ****
                  return (SET_ERROR(EINVAL));
  
          at = strchr(zc->zc_name, '@');
          if (at != NULL) {
                  /* snaps must be in same fs */
                  if (strncmp(zc->zc_name, zc->zc_value, at - zc->zc_name + 1))
                          return (SET_ERROR(EXDEV));
                  *at = '\0';
                  if (zc->zc_objset_type == DMU_OST_ZFS) {
!                         int error = dmu_objset_find(zc->zc_name,
                              recursive_unmount, at + 1,
                              recursive ? DS_FIND_CHILDREN : 0);
!                         if (error != 0)
                                  return (error);
                  }
!                 return (dsl_dataset_rename_snapshot(zc->zc_name,
!                     at + 1, strchr(zc->zc_value, '@') + 1, recursive));
          } else {
                  if (zc->zc_objset_type == DMU_OST_ZVOL)
                          (void) zvol_remove_minor(zc->zc_name);
                  return (dsl_dir_rename(zc->zc_name, zc->zc_value));
          }
--- 3550,3578 ----
                  return (SET_ERROR(EINVAL));
  
          at = strchr(zc->zc_name, '@');
          if (at != NULL) {
                  /* snaps must be in same fs */
+                 int error;
+ 
                  if (strncmp(zc->zc_name, zc->zc_value, at - zc->zc_name + 1))
                          return (SET_ERROR(EXDEV));
                  *at = '\0';
                  if (zc->zc_objset_type == DMU_OST_ZFS) {
!                         error = dmu_objset_find(zc->zc_name,
                              recursive_unmount, at + 1,
                              recursive ? DS_FIND_CHILDREN : 0);
!                         if (error != 0) {
!                                 *at = '@';
                                  return (error);
                          }
!                 }
!                 error = dsl_dataset_rename_snapshot(zc->zc_name,
!                     at + 1, strchr(zc->zc_value, '@') + 1, recursive);
!                 *at = '@';
! 
!                 return (error);
          } else {
                  if (zc->zc_objset_type == DMU_OST_ZVOL)
                          (void) zvol_remove_minor(zc->zc_name);
                  return (dsl_dir_rename(zc->zc_name, zc->zc_value));
          }