Merge branch 'smc-fixes'

Dust Li says:

====================
net/smc: fix kernel panic caused by race of smc_sock

This patchset fixes the race between smc_release triggered by
close(2) and cdc_handle triggered by underlaying RDMA device.

The race is caused because the smc_connection may been released
before the pending tx CDC messages got its CQEs. In order to fix
this, I add a counter to track how many pending WRs we have posted
through the smc_connection, and only release the smc_connection
after there is no pending WRs on the connection.

The first patch prevents posting WR on a QP that is not in RTS
state. This patch is needed because if we post WR on a QP that
is not in RTS state, ib_post_send() may success but no CQE will
return, and that will confuse the counter tracking the pending
WRs.

The second patch add a counter to track how many WRs were posted
through the smc_connection, and don't reset the QP on link destroying
to prevent leak of the counter.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 28 deletions

diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index 99acd337ba90..84c8a4374fdd 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -31,10 +31,6 @@ static void smc_cdc_tx_handler(struct smc_wr_tx_pend_priv *pnd_snd,
 	struct smc_sock *smc;
 	int diff;
 
-	if (!conn)
-		/* already dismissed */
-		return;
-
 	smc = container_of(conn, struct smc_sock, conn);
 	bh_lock_sock(&smc->sk);
 	if (!wc_status) {
@@ -51,6 +47,12 @@ static void smc_cdc_tx_handler(struct smc_wr_tx_pend_priv *pnd_snd,
 			      conn);
 		conn->tx_cdc_seq_fin = cdcpend->ctrl_seq;
 	}
+
+	if (atomic_dec_and_test(&conn->cdc_pend_tx_wr) &&
+	    unlikely(wq_has_sleeper(&conn->cdc_pend_tx_wq)))
+		wake_up(&conn->cdc_pend_tx_wq);
+	WARN_ON(atomic_read(&conn->cdc_pend_tx_wr) < 0);
+
 	smc_tx_sndbuf_nonfull(smc);
 	bh_unlock_sock(&smc->sk);
 }
@@ -107,6 +109,10 @@ int smc_cdc_msg_send(struct smc_connection *conn,
 	conn->tx_cdc_seq++;
 	conn->local_tx_ctrl.seqno = conn->tx_cdc_seq;
 	smc_host_msg_to_cdc((struct smc_cdc_msg *)wr_buf, conn, &cfed);
+
+	atomic_inc(&conn->cdc_pend_tx_wr);
+	smp_mb__after_atomic(); /* Make sure cdc_pend_tx_wr added before post */
+
 	rc = smc_wr_tx_send(link, (struct smc_wr_tx_pend_priv *)pend);
 	if (!rc) {
 		smc_curs_copy(&conn->rx_curs_confirmed, &cfed, conn);
@@ -114,6 +120,7 @@ int smc_cdc_msg_send(struct smc_connection *conn,
 	} else {
 		conn->tx_cdc_seq--;
 		conn->local_tx_ctrl.seqno = conn->tx_cdc_seq;
+		atomic_dec(&conn->cdc_pend_tx_wr);
 	}
 
 	return rc;
@@ -136,7 +143,18 @@ int smcr_cdc_msg_send_validation(struct smc_connection *conn,
 	peer->token = htonl(local->token);
 	peer->prod_flags.failover_validation = 1;
 
+	/* We need to set pend->conn here to make sure smc_cdc_tx_handler()
+	 * can handle properly
+	 */
+	smc_cdc_add_pending_send(conn, pend);
+
+	atomic_inc(&conn->cdc_pend_tx_wr);
+	smp_mb__after_atomic(); /* Make sure cdc_pend_tx_wr added before post */
+
 	rc = smc_wr_tx_send(link, (struct smc_wr_tx_pend_priv *)pend);
+	if (unlikely(rc))
+		atomic_dec(&conn->cdc_pend_tx_wr);
+
 	return rc;
 }
 
@@ -193,31 +211,9 @@ int smc_cdc_get_slot_and_msg_send(struct smc_connection *conn)
 	return rc;
 }
 
-static bool smc_cdc_tx_filter(struct smc_wr_tx_pend_priv *tx_pend,
-			      unsigned long data)
+void smc_cdc_wait_pend_tx_wr(struct smc_connection *conn)
 {
-	struct smc_connection *conn = (struct smc_connection *)data;
-	struct smc_cdc_tx_pend *cdc_pend =
-		(struct smc_cdc_tx_pend *)tx_pend;
-
-	return cdc_pend->conn == conn;
-}
-
-static void smc_cdc_tx_dismisser(struct smc_wr_tx_pend_priv *tx_pend)
-{
-	struct smc_cdc_tx_pend *cdc_pend =
-		(struct smc_cdc_tx_pend *)tx_pend;
-
-	cdc_pend->conn = NULL;
-}
-
-void smc_cdc_tx_dismiss_slots(struct smc_connection *conn)
-{
-	struct smc_link *link = conn->lnk;
-
-	smc_wr_tx_dismiss_slots(link, SMC_CDC_MSG_TYPE,
-				smc_cdc_tx_filter, smc_cdc_tx_dismisser,
-				(unsigned long)conn);
+	wait_event(conn->cdc_pend_tx_wq, !atomic_read(&conn->cdc_pend_tx_wr));
 }
 
 /* Send a SMC-D CDC header.