As the storage capacity of mobile devices increases rapidly, the number of multimedia files stored in each mobile device increases, too. The large number of multimedia files necessitates convenient semantic search interfaces in filesystem. In this work, we develop a novel semantic multimedia filesystem for mobile multimedia devices, SMFS, which is specifically designed for NAND flash memory-based storage devices. SMFS provides convenience to application developers by supporting semantic file search. SMFS outperforms other well-known attribute-rich filesystems and file search programs in terms of file and index creation time, while providing reasonable file search time.