disk_io.c 2603

if (!(fs_info->workers && fs_info->delalloc_workers &&
  fs_info->submit_workers && fs_info->flush_workers &&
  fs_info->endio_workers && fs_info->endio_meta_workers &&
  fs_info->endio_meta_write_workers &&
  fs_info->endio_write_workers && fs_info->endio_raid56_workers &&
  fs_info->endio_freespace_worker && fs_info->rmw_workers &&
  fs_info->caching_workers && fs_info->readahead_workers &&
  fs_info->fixup_workers && fs_info->delayed_workers &&  // <===
  fs_info->fixup_workers && fs_info->extent_workers &&   // <===
  fs_info->qgroup_rescan_workers)) {
    err = -ENOMEM;
    goto fail_sb_buffer;
}