By default, XFS will use 32 bit inode numbers.

If the system supports it, the -o inode64 option to mount to allow 64 bit inode numbers.

Once an inode has been written somewhere on the disk that requires a 64 bit inode number, the file system can no longer be used with 32 bit inode numbers

(IRIX can move inodes to 32 bit numbers with xfs_reno, this tool has not been ported to Linux, yet)