4101 metaslab_debug should allow for fine-grained control
4102 space_maps should store more information about themselves
4103 space map object blocksize should be increased
4104 ::spa_space no longer works
4105 removing a mirrored log device results in a leaked object
4106 asynchronously load metaslab
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Sebastien Roy <seb@delphix.com>

*** 5334,5344 ****
                   * If the pool is suspended then fail immediately. Otherwise,
                   * check to see if the pool is making any progress. If
                   * vdev_deadman() discovers that there hasn't been any recent
                   * I/Os then it will end up aborting the tests.
                   */
!                 if (spa_suspended(spa)) {
                          fatal(0, "aborting test after %llu seconds because "
                              "pool has transitioned to a suspended state.",
                              zfs_deadman_synctime_ms / 1000);
                          return (NULL);
                  }
--- 5334,5344 ----
                   * If the pool is suspended then fail immediately. Otherwise,
                   * check to see if the pool is making any progress. If
                   * vdev_deadman() discovers that there hasn't been any recent
                   * I/Os then it will end up aborting the tests.
                   */
!                 if (spa_suspended(spa) || spa->spa_root_vdev == NULL) {
                          fatal(0, "aborting test after %llu seconds because "
                              "pool has transitioned to a suspended state.",
                              zfs_deadman_synctime_ms / 1000);
                          return (NULL);
                  }