FAT32 filesystems to be mounted, subject to some fairly serious limitations. This works by extending the internal pseudo-inode-numbers generated from the file's starting cluster number to 64-bits, then creating a table mapping these into arbitrary 32-bit inode numbers, which can fit in struct dirent's d_fileno and struct vattr's va_fileid fields. The mappings do not persist across unmounts or reboots, so it's not possible to export these filesystems through NFS. The mapping table may grow to be rather large, and may grow large enough to exhaust kernel memory on filesystems with millions of files. Don't enable this option unless you understand the consequences.