The virtual member function handler::reset_auto_increment(ulonglong) is only ever invoked by the default implementation of handler::truncate():

  virtual int truncate()

  {

    int error= delete_all_rows();

    return error ? error : reset_auto_increment(0);

  }

All derived implementations of handler::reset_auto_increment() as well as the wrapper handler::ha_reset_auto_increment() only seem to serve this use case.

The functions ha_innobase::innobase_reset_autoinc() and ha_innobase::reset_auto_increment() are actually unreachable, because ha_innobase::truncate() never invokes handler::truncate().

Also, ha_innobase::delete_all_rows() unnecessarily overrides handler::delete_all_rows().