net/smc: improve abnormal termination of link groups

If a link group and its connections must be terminated,
* wake up socket waiters
* do not enable buffer reuse

A linkgroup might be terminated while normal connection closing
is running. Avoid buffer reuse and its related LLC DELETE RKEY
call, if linkgroup termination has started. And use the earliest
indication of linkgroup termination possible, namely the removal
from the linkgroup list.
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>

net/smc/smc_core.c

@@ -154,6 +154,7 @@ static void smc_lgr_unregister_conn(struct smc_connection *conn)
 		__smc_lgr_unregister_conn(conn);
 	}
 	write_unlock_bh(&lgr->conns_lock);
+	conn->lgr = NULL;
 }
 
 /* Send delete link, either as client to request the initiation
@@ -344,7 +345,7 @@ static void smc_buf_unuse(struct smc_connection *conn,
 		conn->sndbuf_desc->used = 0;
 	if (conn->rmb_desc) {
 		if (!conn->rmb_desc->regerr) {
-			if (!lgr->is_smcd) {
+			if (!lgr->is_smcd && !list_empty(&lgr->list)) {
 				/* unregister rmb with peer */
 				smc_llc_do_delete_rkey(
 						&lgr->lnk[SMC_SINGLE_LINK],
@@ -375,9 +376,10 @@ void smc_conn_free(struct smc_connection *conn)
 	} else {
 		smc_cdc_tx_dismiss_slots(conn);
 	}
-	smc_lgr_unregister_conn(conn);
-	smc_buf_unuse(conn, lgr);		/* allow buffer reuse */
-	conn->lgr = NULL;
+	if (!list_empty(&lgr->list)) {
+		smc_lgr_unregister_conn(conn);
+		smc_buf_unuse(conn, lgr); /* allow buffer reuse */
+	}
 
 	if (!lgr->conns_num)
 		smc_lgr_schedule_free_work(lgr);
@@ -491,6 +493,28 @@ void smc_lgr_forget(struct smc_link_group *lgr)
 	spin_unlock_bh(lgr_lock);
 }
 
+static void smc_sk_wake_ups(struct smc_sock *smc)
+{
+	smc->sk.sk_write_space(&smc->sk);
+	smc->sk.sk_data_ready(&smc->sk);
+	smc->sk.sk_state_change(&smc->sk);
+}
+
+/* kill a connection */
+static void smc_conn_kill(struct smc_connection *conn)
+{
+	struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
+
+	smc_close_abort(conn);
+	conn->killed = 1;
+	smc_sk_wake_ups(smc);
+	smc_lgr_unregister_conn(conn);
+	smc->sk.sk_err = ECONNABORTED;
+	sock_hold(&smc->sk); /* sock_put in close work */
+	if (!schedule_work(&conn->close_work))
+		sock_put(&smc->sk);
+}
+
 /* terminate link group */
 static void __smc_lgr_terminate(struct smc_link_group *lgr)
 {
@@ -512,13 +536,7 @@ static void __smc_lgr_terminate(struct smc_link_group *lgr)
 		conn = rb_entry(node, struct smc_connection, alert_node);
 		smc = container_of(conn, struct smc_sock, conn);
 		lock_sock(&smc->sk);
-		sock_hold(&smc->sk); /* sock_put in close work */
-		smc_close_abort(conn);
-		conn->killed = 1;
-		smc_lgr_unregister_conn(conn);
-		conn->lgr = NULL;
-		if (!schedule_work(&conn->close_work))
-			sock_put(&smc->sk);
+		smc_conn_kill(conn);
 		release_sock(&smc->sk);
 		read_lock_bh(&lgr->conns_lock);
 		node = rb_first(&lgr->conns_all);