mfs.c: Correctly return buffer when calling MFS_Read()
mfs.c: Make sure input buffer will fit in command when calling MFS_Write()
server.c: Check if inode is allocated and whether type is valid in handle_read()
server.c: Fix invalid output pointer in handle_read() when target is a directory
server.c: In handle_write(), only increment the number of blocks when the
requested block number is just beyond the current largest block number
server.c: Fix directory emptiness check in handle_unlink()
server.c: Make unlinking nonexistent files return success
server.c: Verify the validity of pinum in handle_unlink()
server.c: Fix directory emptiness check in handle_unlink()
server.c: Make handle_unlink() write parent inode back to disk
server.c: Fix search upper bound in handle_lookup()