[PATCH v2] nvmet-tcp: fix data digest calculation for multiple H2CData PDUs

[Varun Prakash]

>> 
>>>> +{
>>>> +	struct scatterlist *sg = &cmd->req.sg[cmd->sg_idx];
>>>> +	struct bio_vec *iov = cmd->iov;
>>>> +	u32 data_length = cmd->pdu_len;
>>>> +
>>>> +	crypto_ahash_init(hash);
>>>> +
>>>> +	if (iov->bv_offset) {
>>>> +		struct scatterlist first_sg;
>>>> +
>>>> +		sg_init_table(&first_sg, 1);
>>>> +		sg_set_page(&first_sg, sg_page(sg), iov->bv_len,
>>>> +				iov->bv_offset);
>>>> +
>>>> +		data_length -= iov->bv_len;
>>>> +
>>>> +		if (data_length) {
>>>> +			ahash_request_set_crypt(hash, &first_sg, NULL,
>>>> +						iov->bv_len);
>>>> +			crypto_ahash_update(hash);
>>>> +			sg = sg_next(sg);
>>>> +		} else {
>>>> +			ahash_request_set_crypt(hash, &first_sg,
>>>> +					(void *)&cmd->exp_ddgst, iov->bv_len);
>>>> +			crypto_ahash_finup(hash);
>>>> +			return;
>>>> +		}
>>>
>>> What is the case for data_length=0 ? I'm not entirely clear how this can
>>> happen.
>> 
>> This can happen if H2CData PDU data length is not a multiple of target page size.
>> 
>> For example if transfer length is 32K, page size is 4K and H2CData PDU data length is 6K,
>> host will send 6 H2CData PDUs, for the last PDU iov->bv_offset = 2K,
>> iov->bv_len = 2K and data_length = 2K.
>
>I understand.
>
>Looking into this, I'm almost thinking we should just give up and
>iterate. at this point it unnecessarily complicates the code...

Should I resend v1?