Method handle_client_request_forward

src/client/Client.cc:2924–2978

void Client::handle_client_request_forward(const MConstRef<MClientRequestForward>& fwd)
{
  mds_rank_t mds = mds_rank_t(fwd->get_source().num());

  std::scoped_lock cl(client_lock);
  auto session = _get_mds_session(mds, fwd->get_connection().get());
  if (!session) {
    return;
  }
  ceph_tid_t tid = fwd->get_tid();

  auto it = mds_requests.find(tid);
  if ( it == mds_requests.end()) {
    ldout(cct, 10) << __func__ << " no pending request on tid " << tid << dendl;
    return;
  }

  MetaRequest *request = it->second;
  ceph_assert(request);

  /*
   * Avoid inifinite retrying after overflow.
   *
   * The MDS will increase the fwd count and in client side
   * if the num_fwd is less than the one saved in request
   * that means the MDS is an old version and overflowed of
   * 8 bits.
   */
  auto num_fwd = fwd->get_num_fwd();
  if (num_fwd <= request->num_fwd || (uint32_t)num_fwd >= UINT32_MAX) {
    request->abort(-EMULTIHOP);
    request->caller_cond->notify_all();
    ldout(cct, 0) << __func__ << " request tid " << tid << " new num_fwd "
      << num_fwd << " old num_fwd " << request->num_fwd << ", fwd seq overflow"
      << ", abort it" << dendl;
    return;
  }

  // reset retry counter
  request->retry_attempt = 0;

  // request not forwarded, or dest mds has no session.
  // resend.
  ldout(cct, 10) << __func__ << " tid " << tid
	   << " fwd " << fwd->get_num_fwd() 
	   << " to mds." << fwd->get_dest_mds() 
	   << ", resending to " << fwd->get_dest_mds()
	   << dendl;
  
  request->mds = -1;
  request->item.remove_myself();
  request->num_fwd = num_fwd;
  request->resend_mds = fwd->get_dest_mds();
  request->caller_cond->notify_all();
}

bool Client::is_dir_operation(MetaRequest *req)
{