net/smc: introduce a delay

The number of outstanding work requests is limited. If all work
requests are in use, tx processing is postponed to another scheduling
of the tx worker. Switch to a delayed worker to have a gap for tx
completion queue events before the next retry.
Signed-off-by: NUrsula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/smc/smc.h

@@ -149,7 +149,7 @@ struct smc_connection {
 	atomic_t		sndbuf_space;	/* remaining space in sndbuf */
 	u16			tx_cdc_seq;	/* sequence # for CDC send */
 	spinlock_t		send_lock;	/* protect wr_sends */
-	struct work_struct	tx_work;	/* retry of smc_cdc_msg_send */
+	struct delayed_work	tx_work;	/* retry of smc_cdc_msg_send */
 
 	struct smc_host_cdc_msg	local_rx_ctrl;	/* filled during event_handl.
 						 * .prod cf. TCP rcv_nxt

net/smc/smc_close.c

@@ -208,7 +208,7 @@ int smc_close_active(struct smc_sock *smc)
 	case SMC_ACTIVE:
 		smc_close_stream_wait(smc, timeout);
 		release_sock(sk);
-		cancel_work_sync(&conn->tx_work);
+		cancel_delayed_work_sync(&conn->tx_work);
 		lock_sock(sk);
 		if (sk->sk_state == SMC_ACTIVE) {
 			/* send close request */
@@ -234,7 +234,7 @@ int smc_close_active(struct smc_sock *smc)
 		if (!smc_cdc_rxed_any_close(conn))
 			smc_close_stream_wait(smc, timeout);
 		release_sock(sk);
-		cancel_work_sync(&conn->tx_work);
+		cancel_delayed_work_sync(&conn->tx_work);
 		lock_sock(sk);
 		if (sk->sk_err != ECONNABORTED) {
 			/* confirm close from peer */
@@ -263,7 +263,9 @@ int smc_close_active(struct smc_sock *smc)
 		/* peer sending PeerConnectionClosed will cause transition */
 		break;
 	case SMC_PROCESSABORT:
-		cancel_work_sync(&conn->tx_work);
+		release_sock(sk);
+		cancel_delayed_work_sync(&conn->tx_work);
+		lock_sock(sk);
 		smc_close_abort(conn);
 		sk->sk_state = SMC_CLOSED;
 		smc_close_wait_tx_pends(smc);
@@ -425,7 +427,7 @@ int smc_close_shutdown_write(struct smc_sock *smc)
 	case SMC_ACTIVE:
 		smc_close_stream_wait(smc, timeout);
 		release_sock(sk);
-		cancel_work_sync(&conn->tx_work);
+		cancel_delayed_work_sync(&conn->tx_work);
 		lock_sock(sk);
 		/* send close wr request */
 		rc = smc_close_wr(conn);
@@ -439,7 +441,7 @@ int smc_close_shutdown_write(struct smc_sock *smc)
 		if (!smc_cdc_rxed_any_close(conn))
 			smc_close_stream_wait(smc, timeout);
 		release_sock(sk);
-		cancel_work_sync(&conn->tx_work);
+		cancel_delayed_work_sync(&conn->tx_work);
 		lock_sock(sk);
 		/* confirm close from peer */
 		rc = smc_close_wr(conn);

net/smc/smc_tx.c

@@ -24,6 +24,8 @@
 #include "smc_cdc.h"
 #include "smc_tx.h"
 
+#define SMC_TX_WORK_DELAY	HZ
+
 /***************************** sndbuf producer *******************************/
 
 /* callback implementation for sk.sk_write_space()
@@ -406,7 +408,8 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
 				goto out_unlock;
 			}
 			rc = 0;
-			schedule_work(&conn->tx_work);
+			schedule_delayed_work(&conn->tx_work,
+					      SMC_TX_WORK_DELAY);
 		}
 		goto out_unlock;
 	}
@@ -430,7 +433,7 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
  */
 static void smc_tx_work(struct work_struct *work)
 {
-	struct smc_connection *conn = container_of(work,
+	struct smc_connection *conn = container_of(to_delayed_work(work),
 						   struct smc_connection,
 						   tx_work);
 	struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
@@ -468,7 +471,8 @@ void smc_tx_consumer_update(struct smc_connection *conn)
 		if (!rc)
 			rc = smc_cdc_msg_send(conn, wr_buf, pend);
 		if (rc < 0) {
-			schedule_work(&conn->tx_work);
+			schedule_delayed_work(&conn->tx_work,
+					      SMC_TX_WORK_DELAY);
 			return;
 		}
 		smc_curs_write(&conn->rx_curs_confirmed,
@@ -487,6 +491,6 @@ void smc_tx_consumer_update(struct smc_connection *conn)
 void smc_tx_init(struct smc_sock *smc)
 {
 	smc->sk.sk_write_space = smc_tx_write_space;
-	INIT_WORK(&smc->conn.tx_work, smc_tx_work);
+	INIT_DELAYED_WORK(&smc->conn.tx_work, smc_tx_work);
 	spin_lock_init(&smc->conn.send_lock);
 }