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.
Not sure if I understood your problem correctly but:
You can start with "/" directory and proceed recursively (or any loop for that matter) with children. Compare the inode value with strcut stat.ino_t. Once you find it, open the path/file.
I don't know if there is an easier way or not but you can do this with bash. with ls -i command you can see the inodes too,
$ ls -i
11147622 file.txt
the first column is the inode number, the blow command shows the inodes in current directory
$ ls -i | awk {'print $1'}
so you need to check the inodes from / too all it's subdirectories until find it
ls -iR /
it shows all subdirectories and there files with there inode number
now you should start from / and use awk to or cut command to have the first column(inode number is in the first column) then compare it with the inode you want to find.