code: func (bi *blockIndex) SetStatusFlags(node *blockNode, flags blockStatus) {
  	bi.Lock()
  	node.status |= flags
  	bi.dirty[node] = struct{}{}
  	bi.Unlock()
  }
docs: // SetStatusFlags flips the provided status flags on the block node to on,
  // regardless of whether they were on or off previously. This does not unset any
  // flags currently on.
  //
  // This function is safe for concurrent access.