firewire: core: improve check for local node

My recently added test for a device being local in fw-cdev.c got it
slightly wrong:  Comparisons of node IDs are only valid if the
generation is current, which I forgot to check.  Normally, serialization
by card->lock takes care of this, but a device in FW_DEVICE_GONE state
will necessarily have a wrong generation and invalid node_id.

The "is it local?" check is made 100% correct and simpler now by means
of a struct fw_device flag which is set at fw_device creation.

Besides the fw-cdev site which was to be fixed, there is another site
which can make use of the new flag, and an RFC-2734 driver will benefit
from it too.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/fw-cdev.c

@@ -739,15 +739,11 @@ static void release_descriptor(struct client *client,
 static int ioctl_add_descriptor(struct client *client, void *buffer)
 {
 	struct fw_cdev_add_descriptor *request = buffer;
-	struct fw_card *card = client->device->card;
 	struct descriptor_resource *r;
 	int ret;
 
 	/* Access policy: Allow this ioctl only on local nodes' device files. */
-	spin_lock_irq(&card->lock);
-	ret = client->device->node_id != card->local_node->node_id;
-	spin_unlock_irq(&card->lock);
-	if (ret)
+	if (!client->device->is_local)
 		return -ENOSYS;
 
 	if (request->length > 256)

drivers/firewire/fw-device.c

@@ -1042,6 +1042,7 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
 		device->node = fw_node_get(node);
 		device->node_id = node->node_id;
 		device->generation = card->generation;
+		device->is_local = node == card->local_node;
 		mutex_init(&device->client_list_mutex);
 		INIT_LIST_HEAD(&device->client_list);
 
@@ -1075,7 +1076,7 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
 			    FW_DEVICE_INITIALIZING) == FW_DEVICE_RUNNING) {
 			PREPARE_DELAYED_WORK(&device->work, fw_device_refresh);
 			schedule_delayed_work(&device->work,
-				node == card->local_node ? 0 : INITIAL_DELAY);
+				device->is_local ? 0 : INITIAL_DELAY);
 		}
 		break;
 

drivers/firewire/fw-device.h

@@ -80,6 +80,7 @@ struct fw_device {
 	u32 *config_rom;
 	size_t config_rom_length;
 	int config_rom_retries;
+	unsigned is_local:1;
 	unsigned cmc:1;
 	unsigned bc_implemented:2;