From: Ursula Braun <ubraun@linux.ibm.com>
Date: Mon, 21 Oct 2019 16:13:10 +0200
Subject: net/smc: improve abnormal termination locking
Git-commit: 69318b5215f2dc32c345a3d65b98b4b1bf29c007
Patch-mainline: v5.5-rc1
References: jsc#SLE-7395

Locking hierarchy requires that the link group conns_lock can be
taken if the socket lock is held, but not vice versa. Nevertheless
socket termination during abnormal link group termination should
be protected by the socket lock.
This patch reduces the time segments the link group conns_lock is
held to enable usage of lock_sock in smc_lgr_terminate().

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>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 net/smc/smc_core.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -491,23 +491,26 @@ static void __smc_lgr_terminate(struct s
 	if (!lgr->is_smcd)
 		smc_llc_link_inactive(&lgr->lnk[SMC_SINGLE_LINK]);
 
-	write_lock_bh(&lgr->conns_lock);
+	/* kill remaining link group connections */
+	read_lock_bh(&lgr->conns_lock);
 	node = rb_first(&lgr->conns_all);
 	while (node) {
+		read_unlock_bh(&lgr->conns_lock);
 		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 */
 		conn->killed = 1;
 		conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
-		__smc_lgr_unregister_conn(conn);
+		smc_lgr_unregister_conn(conn);
 		conn->lgr = NULL;
-		write_unlock_bh(&lgr->conns_lock);
 		if (!schedule_work(&conn->close_work))
 			sock_put(&smc->sk);
-		write_lock_bh(&lgr->conns_lock);
+		release_sock(&smc->sk);
+		read_lock_bh(&lgr->conns_lock);
 		node = rb_first(&lgr->conns_all);
 	}
-	write_unlock_bh(&lgr->conns_lock);
+	read_unlock_bh(&lgr->conns_lock);
 	if (!lgr->is_smcd)
 		wake_up(&lgr->lnk[SMC_SINGLE_LINK].wr_reg_wait);
 	smc_lgr_schedule_free_work(lgr);