For decades, computer architectures have treated memory and storage as separate entities. Nowadays, we watch the emergence of new memory technologies that promise to significantly change the landscape of memory systems. Byte-addressable non-volatile memory (NVM) technologies are expected to offer access latency close to that of dynamic random access memory and capacity suited for storage, resulting in storage-class memory. However, they also present some limitations, such as limited endurance and asymmetric read and write latency. Furthermore, adjusting the current hardware and software architectures to embrace these new memories in all their potential is proving to be a challenge in itself. In this paper, recent studies are analyzed to map the state-of-the-art of NVM file systems research. To achieve this goal, over 100 studies related to NVM systems were selected, analyzed, and categorized according to their topics and contributions. From the information extracted from these papers, we derive the main concerns and challenges currently being studied and discussed in the academia and industry, as well as the trends and solutions being proposed to address them.