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

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On 12.10.23 04:49, D. Wythe wrote:


On 10/12/23 4:37 AM, Wenjia Zhang wrote:


On 11.10.23 09:33, D. Wythe wrote:
From: "D. Wythe" <alibuda@xxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxx>
---
  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?


It can not guarantee he sndbuf_desc would not be NULL, but it will prevents
the smc_cdc_tx_handler() to access a NULL sndbuf_desc. So that we
can avoid the panic descried in commit 22a825c541d7
("net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()").

got it, thanks!

Reviewed-by: Wenjia Zhang <wenjia@xxxxxxxxxxxxx>

&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++;




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