btrfs: add authenticated plus secondary checksum for sha256 and blake2b

Add two new checksums that implemented authenticated checksum with an
additional plain hash.

They can be selected as 'authsum-sha256' or 'authsum-blake2b', where the
secondary hash is always xxhash64.

The point is to provide basic verification of metadata and data blocks
when the authentication key is not available.

Signed-off-by: David Sterba <>
2 files changed