will be called before any other function,
fc_check()will be called to check filesystem specific parameters,
fc_getsizestruct()will be called to get info about space needed during conversion
fc_superblock()if not successful then continues with consecutive calls, called optionally (for same filesystems and locations),
fc_mkfs()is called right before any `export'-specific functions that follow below.
fc_fsdone()when Surprise is done with export of this filesystem. Any filesystem buffers should be flushed now to the disk. Physical media sync (
sync(2)) is not needed to be performed by filesystem module.