Inode numbers in XFS come in two forms: AG relative and absolute.

AG relative inode numbers always fit within 32 bits. The number of bits actually used is determined by the sum of the superblock's (Section 3.1, “Superblocks”) sb_inoplog and sb_agblklog values. Relative inode numbers are found within the AG's inode structures.

Absolute inode numbers include the AG number in the high bits, above the bits used for the AG relative inode number. Absolute inode numbers are found in directory (Chapter 6, Directories) entries.