netdev - Re: [PATCH net 2/3] net/smc: allow cdc msg send rather than drop it with NULL sndbuf

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Date: Wed, 1 Nov 2023 16:36:52 +0800
From: "D. Wythe" <alibuda@...ux.alibaba.com>
To: dust.li@...ux.alibaba.com, kgraul@...ux.ibm.com, wenjia@...ux.ibm.com,
 jaka@...ux.ibm.com, wintera@...ux.ibm.com
Cc: kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
 linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net 2/3] net/smc: allow cdc msg send rather than drop it
 with NULL sndbuf_desc




On 11/1/23 4:19 PM, Dust Li wrote:
> On Wed, Nov 01, 2023 at 11:42:56AM +0800, D. Wythe wrote:
>> From: "D. Wythe" <alibuda@...ux.alibaba.com>
>>
>> This patch re-fix the issues memtianed by commit 22a825c541d7
> memtianed -> mentioned ?
>
>> ("net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()").
>>
>> Blocking sending message do solve the issues though, but it also
>> prevents the peer to receive the final message. Besides, in logic,
>> whether the sndbuf_desc is NULL or not have no impact on the processing
>> of cdc message sending.
>>
>> Hence that, this patch allow the cdc message sending but to check the
> allows
>
>> sndbuf_desc with care in smc_cdc_tx_handler().
>>
>> Fixes: 22a825c541d7 ("net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()")
>> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com>
>> Reviewed-by: Wenjia Zhang <wenjia@...ux.ibm.com>

Thanks for that. I will fix them in next version.

> Reviewed-by: Dust Li <dust.li@...ux.alibaba.com>
>> ---
>> net/smc/smc_cdc.c | 9 ++++-----
>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
>> index 01bdb79..3c06625 100644
>> --- a/net/smc/smc_cdc.c
>> +++ b/net/smc/smc_cdc.c
>> @@ -28,13 +28,15 @@ static void smc_cdc_tx_handler(struct smc_wr_tx_pend_priv *pnd_snd,
>> {
>> 	struct smc_cdc_tx_pend *cdcpend = (struct smc_cdc_tx_pend *)pnd_snd;
>> 	struct smc_connection *conn = cdcpend->conn;
>> +	struct smc_buf_desc *sndbuf_desc;
>> 	struct smc_sock *smc;
>> 	int diff;
>>
>> +	sndbuf_desc = conn->sndbuf_desc;
>> 	smc = container_of(conn, struct smc_sock, conn);
>> 	bh_lock_sock(&smc->sk);
>> -	if (!wc_status) {
>> -		diff = smc_curs_diff(cdcpend->conn->sndbuf_desc->len,
>> +	if (!wc_status && sndbuf_desc) {
>> +		diff = smc_curs_diff(sndbuf_desc->len,
>> 				     &cdcpend->conn->tx_curs_fin,
>> 				     &cdcpend->cursor);
>> 		/* sndbuf_space is decreased in smc_sendmsg */
>> @@ -114,9 +116,6 @@ int smc_cdc_msg_send(struct smc_connection *conn,
>> 	union smc_host_cursor cfed;
>> 	int rc;
>>
>> -	if (unlikely(!READ_ONCE(conn->sndbuf_desc)))
>> -		return -ENOBUFS;
>> -
>> 	smc_cdc_add_pending_send(conn, pend);
>>
>> 	conn->tx_cdc_seq++;
>> -- 
>> 1.8.3.1