Re: [PATCH net-next v6 10/11] net/smc: adapt cursor update when sndbuf and peer DMB are merged

Wen Gu
2024-04-16T14:06:10Z

On 2024/4/16 19:05, Simon Horman wrote:
> On Sun, Apr 14, 2024 at 12:03:03PM +0800, Wen Gu wrote:
>> If the local sndbuf shares the same physical memory with peer DMB,
>> the cursor update processing needs to be adapted to ensure that the
>> data to be consumed won't be overwritten.
>>
>> So in this case, the fin_curs and sndbuf_space that were originally
>> updated after sending the CDC message should be modified to not be
>> update until the peer updates cons_curs.
>>
>> Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
>
> ...
>
>> @@ -255,6 +256,14 @@ int smcd_cdc_msg_send(struct smc_connection *conn)
>> return rc;
>> smc_curs_copy(&conn->rx_curs_confirmed, &curs, conn);
>> conn->local_rx_ctrl.prod_flags.cons_curs_upd_req = 0;
>> +
>> + if (smc_ism_support_dmb_nocopy(conn->lgr->smcd))
>> + /* if local sndbuf shares the same memory region with
>> + * peer DMB, then don't update the tx_curs_fin
>> + * and sndbuf_space until peer has consumed the data.
>> + */
>> + return rc;
>
> Hi Wen Gu,
>
> A minor nit from my side:
>
> To my mind "return rc" implies returning an error value.
> But here rc is 0, which based on the comment seems correct.
> So perhaps it would be clearer to simply return 0.
>
> Flagged by Smatch.
>
>> +
>> /* Calculate transmitted data and increment free send buffer space */
>> diff = smc_curs_diff(conn->sndbuf_desc->len, &conn->tx_curs_fin,
>> &conn->tx_curs_sent);
>
> ...

OK. I will improve it and another 'return rc' at the end of
smcd_cdc_msg_send(). Thanks! Simon.