rxrpc: Make the local endpoint hold a ref on a connected call

Make the local endpoint and it's I/O thread hold a reference on a connected
call until that call is disconnected.  Without this, we're reliant on
either the AF_RXRPC socket to hold a ref (which is dropped when the call is
released) or a queued work item to hold a ref (the work item is being
replaced with the I/O thread).
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

include/trace/events/rxrpc.h

@@ -148,6 +148,7 @@
 	E_(rxrpc_client_to_idle,		"->Idle")
 
 #define rxrpc_call_traces \
+	EM(rxrpc_call_get_io_thread,		"GET iothread") \
 	EM(rxrpc_call_get_input,		"GET input   ") \
 	EM(rxrpc_call_get_kernel_service,	"GET krnl-srv") \
 	EM(rxrpc_call_get_notify_socket,	"GET notify  ") \
@@ -160,6 +161,7 @@
 	EM(rxrpc_call_new_prealloc_service,	"NEW prealloc") \
 	EM(rxrpc_call_put_discard_prealloc,	"PUT disc-pre") \
 	EM(rxrpc_call_put_discard_error,	"PUT disc-err") \
+	EM(rxrpc_call_put_io_thread,		"PUT iothread") \
 	EM(rxrpc_call_put_input,		"PUT input   ") \
 	EM(rxrpc_call_put_kernel,		"PUT kernel  ") \
 	EM(rxrpc_call_put_poke,			"PUT poke    ") \
@@ -173,6 +175,7 @@
 	EM(rxrpc_call_see_activate_client,	"SEE act-clnt") \
 	EM(rxrpc_call_see_connect_failed,	"SEE con-fail") \
 	EM(rxrpc_call_see_connected,		"SEE connect ") \
+	EM(rxrpc_call_see_disconnected,		"SEE disconn ") \
 	EM(rxrpc_call_see_distribute_error,	"SEE dist-err") \
 	EM(rxrpc_call_see_input,		"SEE input   ") \
 	EM(rxrpc_call_see_release,		"SEE release ") \

net/rxrpc/call_object.c

@@ -453,6 +453,8 @@ void rxrpc_incoming_call(struct rxrpc_sock *rx,
 		BUG();
 	}
 
+	rxrpc_get_call(call, rxrpc_call_get_io_thread);
+
 	/* Set the channel for this call.  We don't get channel_lock as we're
 	 * only defending against the data_ready handler (which we're called
 	 * from) and the RESPONSE packet parser (which is only really

net/rxrpc/conn_client.c

@@ -725,8 +725,11 @@ int rxrpc_connect_call(struct rxrpc_sock *rx,
 
 	rxrpc_discard_expired_client_conns(&rxnet->client_conn_reaper);
 
+	rxrpc_get_call(call, rxrpc_call_get_io_thread);
+
 	bundle = rxrpc_prep_call(rx, call, cp, srx, gfp);
 	if (IS_ERR(bundle)) {
+		rxrpc_put_call(call, rxrpc_call_get_io_thread);
 		ret = PTR_ERR(bundle);
 		goto out;
 	}
@@ -820,7 +823,6 @@ void rxrpc_disconnect_client_call(struct rxrpc_bundle *bundle, struct rxrpc_call
 	_enter("c=%x", call->debug_id);
 
 	spin_lock(&bundle->channel_lock);
-	set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
 
 	/* Calls that have never actually been assigned a channel can simply be
 	 * discarded.
@@ -912,8 +914,6 @@ void rxrpc_disconnect_client_call(struct rxrpc_bundle *bundle, struct rxrpc_call
 
 out:
 	spin_unlock(&bundle->channel_lock);
-	_leave("");
-	return;
 }
 
 /*

net/rxrpc/conn_object.c

@@ -178,6 +178,9 @@ void rxrpc_disconnect_call(struct rxrpc_call *call)
 {
 	struct rxrpc_connection *conn = call->conn;
 
+	set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
+	rxrpc_see_call(call, rxrpc_call_see_disconnected);
+
 	call->peer->cong_ssthresh = call->cong_ssthresh;
 
 	if (!hlist_unhashed(&call->error_link)) {
@@ -186,18 +189,20 @@ void rxrpc_disconnect_call(struct rxrpc_call *call)
 		spin_unlock(&call->peer->lock);
 	}
 
-	if (rxrpc_is_client_call(call))
-		return rxrpc_disconnect_client_call(conn->bundle, call);
+	if (rxrpc_is_client_call(call)) {
+		rxrpc_disconnect_client_call(conn->bundle, call);
+	} else {
+		spin_lock(&conn->bundle->channel_lock);
+		__rxrpc_disconnect_call(conn, call);
+		spin_unlock(&conn->bundle->channel_lock);
 
-	spin_lock(&conn->bundle->channel_lock);
-	__rxrpc_disconnect_call(conn, call);
-	spin_unlock(&conn->bundle->channel_lock);
+		conn->idle_timestamp = jiffies;
+		if (atomic_dec_and_test(&conn->active))
+			rxrpc_set_service_reap_timer(conn->rxnet,
+						     jiffies + rxrpc_connection_expiry);
+	}
 
-	set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
-	conn->idle_timestamp = jiffies;
-	if (atomic_dec_and_test(&conn->active))
-		rxrpc_set_service_reap_timer(conn->rxnet,
-					     jiffies + rxrpc_connection_expiry);
+	rxrpc_put_call(call, rxrpc_call_put_io_thread);
 }
 
 /*