rds: clean up loopback rds_connections on netns deletion

The RDS core module creates rds_connections based on callbacks
from rds_loop_transport when sending/receiving packets to local
addresses.

These connections will need to be cleaned up when they are
created from a netns that is not init_net, and that netns is deleted.

Add the changes aligned with the changes from
commit ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize
netns/module teardown and rds connection/workq management") for
rds_loop_transport

Reported-and-tested-by: [e-mail]
Acked-by: Santosh Shilimkar <[e-mail]>
Signed-off-by: Sowmini Varadhan <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/rds/connection.c

···
 
 int rds_conn_init(void)
 {
+	int ret;
+
+	ret = rds_loop_net_init(); /* register pernet callback */
+	if (ret)
+		return ret;
+
 	rds_conn_slab = kmem_cache_create("rds_connection",
 					  sizeof(struct rds_connection),
 					  0, 0, NULL);
-	if (!rds_conn_slab)
+	if (!rds_conn_slab) {
+		rds_loop_net_exit();
 		return -ENOMEM;
+	}
 
 	rds_info_register_func(RDS_INFO_CONNECTIONS, rds_conn_info);
 	rds_info_register_func(RDS_INFO_SEND_MESSAGES,
···
 
 void rds_conn_exit(void)
 {
+	rds_loop_net_exit(); /* unregister pernet callback */
 	rds_loop_exit();
 
 	WARN_ON(!hlist_empty(rds_conn_hash));

net/rds/loop.c

···
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/in.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
 
 #include "rds_single_path.h"
 #include "rds.h"
···
 
 static DEFINE_SPINLOCK(loop_conns_lock);
 static LIST_HEAD(loop_conns);
+static atomic_t rds_loop_unloading = ATOMIC_INIT(0);
+
+static void rds_loop_set_unloading(void)
+{
+	atomic_set(&rds_loop_unloading, 1);
+}
+
+static bool rds_loop_is_unloading(struct rds_connection *conn)
+{
+	return atomic_read(&rds_loop_unloading) != 0;
+}
 
 /*
  * This 'loopback' transport is a special case for flows that originate
···
 	struct rds_loop_connection *lc, *_lc;
 	LIST_HEAD(tmp_list);
 
+	rds_loop_set_unloading();
+	synchronize_rcu();
 	/* avoid calling conn_destroy with irqs off */
 	spin_lock_irq(&loop_conns_lock);
 	list_splice(&loop_conns, &tmp_list);
···
 		WARN_ON(lc->conn->c_passive);
 		rds_conn_destroy(lc->conn);
 	}
+}
+
+static void rds_loop_kill_conns(struct net *net)
+{
+	struct rds_loop_connection *lc, *_lc;
+	LIST_HEAD(tmp_list);
+
+	spin_lock_irq(&loop_conns_lock);
+	list_for_each_entry_safe(lc, _lc, &loop_conns, loop_node)  {
+		struct net *c_net = read_pnet(&lc->conn->c_net);
+
+		if (net != c_net)
+			continue;
+		list_move_tail(&lc->loop_node, &tmp_list);
+	}
+	spin_unlock_irq(&loop_conns_lock);
+
+	list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
+		WARN_ON(lc->conn->c_passive);
+		rds_conn_destroy(lc->conn);
+	}
+}
+
+static void __net_exit rds_loop_exit_net(struct net *net)
+{
+	rds_loop_kill_conns(net);
+}
+
+static struct pernet_operations rds_loop_net_ops = {
+	.exit = rds_loop_exit_net,
+};
+
+int rds_loop_net_init(void)
+{
+	return register_pernet_device(&rds_loop_net_ops);
+}
+
+void rds_loop_net_exit(void)
+{
+	unregister_pernet_device(&rds_loop_net_ops);
 }
 
 /*
···
 	.inc_free		= rds_loop_inc_free,
 	.t_name			= "loopback",
 	.t_type			= RDS_TRANS_LOOP,
+	.t_unloading		= rds_loop_is_unloading,
 };

net/rds/loop.h

···
 /* loop.c */
 extern struct rds_transport rds_loop_transport;
 
+int rds_loop_net_init(void);
+void rds_loop_net_exit(void);
 void rds_loop_exit(void);
 
 #endif