Widening ext4's readdir() cookie

remember, the OS has no idea when (or even if) the application is going to make it's next request. The spec allows the application to read one filename a week and still be guaranteed to see all files that existed when it started the read with no duplicates.

If there were no resource constraints, the system could use RCU type strategies to make a copy of the directory and just use the token as a numeric offset into this copy, but since the system has no way of ever knowing when it could release this copy, it would have to keep it forever.

remember that with NFS, a server is required to be consistent even across reboots.