On Thu, 6 Dec 2018 at 05:54, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> Log the hash algorithm's driver name when a dm-verity target is created.
> This will help people determine whether the expected implementation is
> being used. It can make an enormous difference; e.g., SHA-256 on ARM
> can be 8x faster with the crypto extensions than without. It can also
> be useful to know if an implementation using an external crypto
> accelerator is being used instead of a software implementation.
>
> Example message:
>
> [ 35.281945] device-mapper: verity: sha256 using implementation "sha256-ce"
>
> We've already found the similar message in fs/crypto/keyinfo.c to be
> very useful.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> drivers/md/dm-verity-target.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> index fc65f0dedf7f..f4c31ffaa88e 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -1040,6 +1040,15 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
> v->tfm = NULL;
> goto bad;
> }
> +
> + /*
> + * dm-verity performance can vary greatly depending on which hash
> + * algorithm implementation is used. Help people debug performance
> + * problems by logging the ->cra_driver_name.
> + */
> + DMINFO("%s using implementation \"%s\"", v->alg_name,
> + crypto_hash_alg_common(v->tfm)->base.cra_driver_name);
> +
> v->digest_size = crypto_ahash_digestsize(v->tfm);
> if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
> ti->error = "Digest size too big";
> --
> 2.19.2
>
