Re: [RFC net-next 5/7] net/ism: Move ism_loopback to net/ism

[Alexandra Winter <wintera@linux.ibm.com>]

On 20.01.25 04:55, Dust Li wrote:
>> +static int ism_lo_move_data(struct ism_dev *ism, u64 dmb_tok,
>> +			    unsigned int idx, bool sf, unsigned int offset,
>> +			    void *data, unsigned int size)
>> +{
>> +	struct ism_lo_dmb_node *rmb_node = NULL, *tmp_node;
>> +	struct ism_lo_dev *ldev;
>> +	u16 s_mask;
>> +	u8 client_id;
>> +	u32 sba_idx;
>> +
>> +	ldev = container_of(ism, struct ism_lo_dev, ism);
>> +
>> +	if (!sf)
>> +		/* since sndbuf is merged with peer DMB, there is
>> +		 * no need to copy data from sndbuf to peer DMB.
>> +		 */
>> +		return 0;
>> +
>> +	read_lock_bh(&ldev->dmb_ht_lock);
>> +	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_tok) {
>> +		if (tmp_node->token == dmb_tok) {
>> +			rmb_node = tmp_node;
>> +			break;
>> +		}
>> +	}
>> +	if (!rmb_node) {
>> +		read_unlock_bh(&ldev->dmb_ht_lock);
>> +		return -EINVAL;
>> +	}
>> +	// So why copy the data now?? SMC usecase? Data buffer is attached,
>> +	// rw-pointer are not attached?
> I understand the confusion here. I have the same confusion the first time
> I saw this.
> 
> This is actually the tricky part: it assumes the CDC will signal, while
> the data will not. We need to copy the CDC, so the copy here only to the
> CDC.
> 
> I think we should refine the move_data() API to make this clearer.
> 
> Best regards,
> Dust

I agree. Will be refined in next version.