Implementing asynchronous file system with FUSE on Linux
(1) Inodes are defined as unsigned integers, so in theory, you could use any values.However, since there could be programs which are not careful, I'd play it safe and only use non-zero, positive integers up to INT_MAX.
(2) Fuse uses a special kernel device. While fuse_chan_recv() do not support partial reads, this may not be required, as kernel should not return partial packets anyway.
(3) Filenames in Linux are max 4096 chars. This puts a limit on a buffer size:
$ grep PATH_MAX /usr/include/linux/limits.h#define PATH_MAX 4096 /* # chars in a path name including nul */