On 2021/04/16 16:13, Johannes Thumshirn wrote:
> On 16/04/2021 05:05, Damien Le Moal wrote:
>
> [...]
>
>> + CRYPT_IV_NO_SECTORS, /* IV calculation does not use sectors
>> */
>
> [...]
>
>> - if (ivmode == NULL)
>> + if (ivmode == NULL) {
>> cc->iv_gen_ops = NULL;
>> - else if (strcmp(ivmode, "plain") == 0)
>> + set_bit(CRYPT_IV_NO_SECTORS, &cc->cipher_flags);
>> + } else if (strcmp(ivmode, "plain") == 0)
>
> [...]
>
>> + if (!test_bit(CRYPT_IV_NO_SECTORS, &cc->cipher_flags)) {
>> + DMWARN("Zone append is not supported with sector-based
>> IV cyphers");
>> + ti->zone_append_not_supported = true;
>> + }
>
> I think this negation is hard to follow, at least I had a hard time
> reviewing it.
>
> Wouldn't it make more sense to use CRYPT_IV_USE_SECTORS, set the bit
> for algorithms that use sectors as IV (like plain64) and then do a
> normal
There are only 2 IV modes that do not use sectors. null and random. All others
do. Hence the "NO_SECTORS" choice. That is the exception rather than the norm,
the flag indicates that.
>
> if (test_bit(CRYPT_IV_USE_SECTORS, &cc->cipher_flags)) {
> DMWARN("Zone append is not supported with sector-based IV
> cyphers");
> ti->zone_append_not_supported = true;
> }
>
> i.e. without the double negation?
Yes. I agree, it is more readable. But adds more lines for the same result. I
could add a small boolean helper to make the "!test_bit(CRYPT_IV_NO_SECTORS,
&cc->cipher_flags)" easier to understand.
>
>
--
Damien Le Moal
Western Digital Research
