In this paper, we consider a full-duplex massive MIMO system which includes a full-duplex BS with a large number of antennas and half-duplex uplink (UL) and downlink (DL) users with a single antenna. Due to the self-interference at the BS, the UL spectral efficiency is significantly decreased. In order to improve the UL spectral efficiency, we focus on the utilization schemes of the spatial resources which can be used to enhance the UL performance. If the BS uses the spatial resources as receive antennas, the BS can obtain an additional receive diversity gain for the UL desired signal. On the other hand, if the BS uses the spatial resources as transmit antennas, the BS can suppress a part of the self-interference by using the extended transmit beamformer including a part of the self-interference channel. Our analysis and numerical results show that there are some tradeoffs between achieving receive diversity gain for the UL desired signal and suppressing the self-interference. According to the system parameters, the utilization schemes of the spatial resources would be determined for maximizing the UL spectral efficiency.