Documentation/filesystems/fscrypt.rst

273 included in the IV.  Moreover:
295 compliant with the UFS standard, which supports only 64 IV bits per
304 logical block number mod 2^32 to produce a 32-bit IV.
307 compliant with the eMMC v5.2 standard, which supports only 32 IV bits
309 format results in some level of IV reuse, so it should only be used
458 Each block's IV is set to the logical block number within the file as
461 - With CBC mode encryption, ESSIV is also used.  Specifically, each IV
465 - With `DIRECT_KEY policies`_, the file's nonce is appended to the IV.
469   to 32 bits and is placed in bits 0-31 of the IV.  The inode number
473   to 32 bits and is placed in bits 0-31 of the IV.  The inode number
485 filenames of up to 255 bytes, the same IV is used for every filename
491 Thus, IV reuse is limited to within a single directory.
493 With CTS-CBC, the IV reuse means that when the plaintext filenames share a
512 that IV reuse is not a problem as each symlink has its own inode.