sctp: remove the dead field of sctp_transport

After we use refcnt to check if transport is alive, the dead can be
removed from sctp_transport.

The traversal of transport_addr_list in procfs dump is using
list_for_each_entry_rcu, no need to check if it has been freed.

sctp_generate_t3_rtx_event and sctp_generate_heartbeat_event is
protected by sock lock, it's not necessary to check dead, either.
also, the timers are cancelled when sctp_transport_free() is
called, that it doesn't wait for refcnt to reach 0 to cancel them.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: lxin

include/net/sctp/structs.h

@@ -756,7 +756,6 @@ struct sctp_transport {
 
 	/* Reference counting. */
 	atomic_t refcnt;
-	__u32	 dead:1,
 		/* RTO-Pending : A flag used to track if one of the DATA
 		 *		chunks sent to this address is currently being
 		 *		used to compute a RTT. If this flag is 0,
@@ -766,7 +765,7 @@ struct sctp_transport {
 		 *		calculation completes (i.e. the DATA chunk
 		 *		is SACK'd) clear this flag.
 		 */
-		 rto_pending:1,
+	__u32	rto_pending:1,
 
 		/*
 		 * hb_sent : a flag that signals that we have a pending

net/sctp/proc.c

@@ -165,8 +165,6 @@ static void sctp_seq_dump_remote_addrs(struct seq_file *seq, struct sctp_associa
 	list_for_each_entry_rcu(transport, &assoc->peer.transport_addr_list,
 			transports) {
 		addr = &transport->ipaddr;
-		if (transport->dead)
-			continue;
 
 		af = sctp_get_af_specific(addr->sa.sa_family);
 		if (af->cmp_addr(addr, primary)) {
@@ -499,8 +497,6 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
 
 	list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list,
 				transports) {
-		if (tsp->dead)
-			continue;
 		/*
 		 * The remote address (ADDR)
 		 */

net/sctp/sm_sideeffect.c

@@ -259,12 +259,6 @@ void sctp_generate_t3_rtx_event(unsigned long peer)
 		goto out_unlock;
 	}
 
-	/* Is this transport really dead and just waiting around for
-	 * the timer to let go of the reference?
-	 */
-	if (transport->dead)
-		goto out_unlock;
-
 	/* Run through the state machine.  */
 	error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT,
 			   SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_T3_RTX),
@@ -380,12 +374,6 @@ void sctp_generate_heartbeat_event(unsigned long data)
 		goto out_unlock;
 	}
 
-	/* Is this structure just waiting around for us to actually
-	 * get destroyed?
-	 */
-	if (transport->dead)
-		goto out_unlock;
-
 	error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT,
 			   SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_HEARTBEAT),
 			   asoc->state, asoc->ep, asoc,

net/sctp/transport.c

@@ -132,8 +132,6 @@ struct sctp_transport *sctp_transport_new(struct net *net,
  */
 void sctp_transport_free(struct sctp_transport *transport)
 {
-	transport->dead = 1;
-
 	/* Try to delete the heartbeat timer.  */
 	if (del_timer(&transport->hb_timer))
 		sctp_transport_put(transport);
@@ -169,7 +167,7 @@ static void sctp_transport_destroy_rcu(struct rcu_head *head)
  */
 static void sctp_transport_destroy(struct sctp_transport *transport)
 {
-	if (unlikely(!transport->dead)) {
+	if (unlikely(atomic_read(&transport->refcnt))) {
 		WARN(1, "Attempt to destroy undead transport %p!\n", transport);
 		return;
 	}