[tipc-discussion] [PATCH net-next v3 02/12] tipc: involve tipc_unregister_media routine

[Ying X. <yin...@wi...>]

When a TIPC media is started, it is registered to be linked into a
global media_list list, however, the media is not removed from the
list when it is stopped. But there has a special case that all TIPC
media instances are declared statically, so it cannot cause serious
problem like memory leak even if media instance is not removed from
the media_list list when TIPC module is unloaded.

As the media_list will be protected by RCU lock, without unregister
routine, we just see how a media instance is linked into media_list,
but cannot find where the media is removed from the list, which is
an very weird design. Therefore, to make TIPC code more readable the
tipc_unregister_media() is introduced to remove media instance from
media_list when TIPC module is stopped.

Signed-off-by: Ying Xue <yin...@wi...>
---
 net/tipc/bearer.c    |   17 +++++++++++++++++
 net/tipc/bearer.h    |    1 +
 net/tipc/eth_media.c |    1 +
 net/tipc/ib_media.c  |    1 +
 4 files changed, 20 insertions(+)

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 17f9824..35e65b5 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -109,6 +109,23 @@ exit:
 	return res;
 }
 
+void tipc_unregister_media(const struct tipc_media *m_ptr)
+{
+	struct tipc_media *m;
+	u32 i;
+
+	write_lock_bh(&tipc_net_lock);
+	for (i = 0; i < media_count; i++) {
+		m = media_list[i];
+		if (m_ptr == m) {
+			media_list[i] = NULL;
+			media_count--;
+			break;
+		}
+	}
+	write_unlock_bh(&tipc_net_lock);
+}
+
 /**
  * tipc_media_addr_printf - record media address in print buffer
  */
diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
index 8695d4a..280c23d 100644
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -160,6 +160,7 @@ extern struct tipc_bearer tipc_bearers[];
  * TIPC routines available to supported media types
  */
 int tipc_register_media(struct tipc_media *m_ptr);
+void tipc_unregister_media(const struct tipc_media *m_ptr);
 
 void tipc_recv_msg(struct sk_buff *buf, struct tipc_bearer *tb_ptr);
 
diff --git a/net/tipc/eth_media.c b/net/tipc/eth_media.c
index 32d01e8..5ba58b0 100644
--- a/net/tipc/eth_media.c
+++ b/net/tipc/eth_media.c
@@ -371,5 +371,6 @@ void tipc_eth_media_stop(void)
 
 	flush_scheduled_work();
 	unregister_netdevice_notifier(&notifier);
+	tipc_unregister_media(&eth_media_info);
 	eth_started = 0;
 }
diff --git a/net/tipc/ib_media.c b/net/tipc/ib_media.c
index 5241a5b..34b9710 100644
--- a/net/tipc/ib_media.c
+++ b/net/tipc/ib_media.c
@@ -367,5 +367,6 @@ void tipc_ib_media_stop(void)
 
 	flush_scheduled_work();
 	unregister_netdevice_notifier(&notifier);
+	tipc_unregister_media(&ib_media_info);
 	ib_started = 0;
 }
-- 
1.7.9.5