We rely on the ino field of fdinfo as a security hardening against fake procfs files, but unfortunately it was added much more recently than I expected -- torvalds/linux@3845f256a8b52 was merged in Linux 5.14 (after openat2!!).

This causes procfs operations to fail on AlmaLinux 8 and similar old-kernel distros. I guess we will just need to rely on mnt_id... You could imagine using flags but those are nowhere near as difficult to fake as ino so we may as well just skip it...