Re: [PATCH net 3/5] net/smc: allow cdc msg send rather than drop it with NULL sndbuf_desc

Wenjia Zhang
2023-10-11T20:37:48Z

On 11.10.23 09:33, D. Wythe wrote:
> From: "D. Wythe" <alibuda@linux.alibaba.com>
>
> This patch re-fix the issues memtianed by commit 22a825c541d7
> ("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.
>
Agree.

> Hence that, this patch allow the cdc message sending but to check the
> 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@linux.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,
How could this guarantee that the sndbuf_desc would not be NULL?

> &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++;