is there any userspace API or third-party kernel module that can help to access file by inode on Linux? 

I'm trying to implement something like:

```
int read_file_by_ino(int ino, int pos, int size, char* buf);
int write_file_by_ino(int ino, int pos, int size, const char* buf);
int readdir_by_ino(...);
int stat_by_ino(...);
...

```

The program is expected to run under root user, so there's no security requirement to do permission checking.