• Sami Tolvanen's avatar
    dm verity: add support for forward error correction · a739ff3f
    Sami Tolvanen authored
    Add support for correcting corrupted blocks using Reed-Solomon.
    This code uses RS(255, N) interleaved across data and hash
    blocks. Each error-correcting block covers N bytes evenly
    distributed across the combined total data, so that each byte is a
    maximum distance away from the others. This makes it possible to
    recover from several consecutive corrupted blocks with relatively
    small space overhead.
    In addition, using verity hashes to locate erasures nearly doubles
    the effectiveness of error correction. Being able to detect
    corrupted blocks also improves performance, because only corrupted
    blocks need to corrected.
    For a 2 GiB partition, RS(255, 253) (two parity bytes for each
    253-byte block) can correct up to 16 MiB of consecutive corrupted
    blocks if erasures can be located, and 8 MiB if they cannot, with
    16 MiB space overhead.
    Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
    Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
dm-verity-fec.h 4.29 KB