void IOBuf::markExternallyShared() {
  IOBuf* current = this;
  do {
    current->markExternallySharedOne();
    current = current->next_;
  } while (current != this);
}
void IOBuf::markExternallyShared() {
  IOBuf* current = this;
  do {
    current->markExternallySharedOne();
    current = current->next_;
  } while (current != this);
}