Commit 376b1aab authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

macvtap: eliminate linear search 



Linear search were used in both get_slot() and macvtap_get_queue(), this is
because:

- macvtap didn't reshuffle the array of taps when create or destroy a queue, so
  when adding a new queue, macvtap must do linear search to find a location for
  the new queue. This will also complicate the TUNSETQUEUE implementation for
  multiqueue API.
- the queue itself didn't track the queue index, so the we must do a linear
  search in the array to find the location of a existed queue.

The solution is straightforward: reshuffle the array and introduce a queue_index
to macvtap_queue.

Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f0afce01

drivers/net/macvtap.c

+20 −44
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ struct macvtap_queue { 
	struct macvlan_dev __rcu *vlan;

	struct file *file;

	unsigned int flags;

	u16 queue_index;

};



static struct proto macvtap_proto = {
@@ -84,30 +85,10 @@ static const struct proto_ops macvtap_socket_ops; 
 */

static DEFINE_SPINLOCK(macvtap_lock);



/*

 * get_slot: return a [unused/occupied] slot in vlan->taps[]:

 *	- if 'q' is NULL, return the first empty slot;

 *	- otherwise, return the slot this pointer occupies.

 */

static int get_slot(struct macvlan_dev *vlan, struct macvtap_queue *q)

{

	int i;



	for (i = 0; i < MAX_MACVTAP_QUEUES; i++) {

		if (rcu_dereference_protected(vlan->taps[i],

					      lockdep_is_held(&macvtap_lock)) == q)

			return i;

	}



	/* Should never happen */

	BUG_ON(1);

}



static int macvtap_set_queue(struct net_device *dev, struct file *file,

				struct macvtap_queue *q)

{

	struct macvlan_dev *vlan = netdev_priv(dev);

	int index;

	int err = -EBUSY;



	spin_lock(&macvtap_lock);
@@ -115,12 +96,12 @@ static int macvtap_set_queue(struct net_device *dev, struct file *file, 
		goto out;



	err = 0;

	index = get_slot(vlan, NULL);

	rcu_assign_pointer(q->vlan, vlan);

	rcu_assign_pointer(vlan->taps[index], q);

	rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);

	sock_hold(&q->sk);



	q->file = file;

	q->queue_index = vlan->numvtaps;

	file->private_data = q;



	vlan->numvtaps++;
@@ -140,15 +121,22 @@ out: 
 */

static void macvtap_put_queue(struct macvtap_queue *q)

{

	struct macvtap_queue *nq;

	struct macvlan_dev *vlan;



	spin_lock(&macvtap_lock);

	vlan = rcu_dereference_protected(q->vlan,

					 lockdep_is_held(&macvtap_lock));

	if (vlan) {

		int index = get_slot(vlan, q);

		int index = q->queue_index;

		BUG_ON(index >= vlan->numvtaps);



		RCU_INIT_POINTER(vlan->taps[index], NULL);

		nq = rcu_dereference_protected(vlan->taps[vlan->numvtaps - 1],

					       lockdep_is_held(&macvtap_lock));

		rcu_assign_pointer(vlan->taps[index], nq);

		nq->queue_index = index;



		RCU_INIT_POINTER(vlan->taps[vlan->numvtaps - 1], NULL);

		RCU_INIT_POINTER(q->vlan, NULL);

		sock_put(&q->sk);

		--vlan->numvtaps;
@@ -182,7 +170,6 @@ static struct macvtap_queue *macvtap_get_queue(struct net_device *dev, 
	rxq = skb_get_rxhash(skb);

	if (rxq) {

		tap = rcu_dereference(vlan->taps[rxq % numvtaps]);

		if (tap)

		goto out;

	}
@@ -193,17 +180,10 @@ static struct macvtap_queue *macvtap_get_queue(struct net_device *dev, 
			rxq -= numvtaps;



		tap = rcu_dereference(vlan->taps[rxq]);

		if (tap)

		goto out;

	}



	/* Everything failed - find first available queue */

	for (rxq = 0; rxq < MAX_MACVTAP_QUEUES; rxq++) {

		tap = rcu_dereference(vlan->taps[rxq]);

		if (tap)

			break;

	}



	tap = rcu_dereference(vlan->taps[0]);

out:

	return tap;

}
@@ -219,19 +199,15 @@ static void macvtap_del_queues(struct net_device *dev) 
	struct macvtap_queue *q, *qlist[MAX_MACVTAP_QUEUES];

	int i, j = 0;



	/* macvtap_put_queue can free some slots, so go through all slots */

	spin_lock(&macvtap_lock);

	for (i = 0; i < MAX_MACVTAP_QUEUES && vlan->numvtaps; i++) {

	for (i = 0; i < vlan->numvtaps; i++) {

		q = rcu_dereference_protected(vlan->taps[i],

					      lockdep_is_held(&macvtap_lock));

		if (q) {

		BUG_ON(q == NULL);

		qlist[j++] = q;

		RCU_INIT_POINTER(vlan->taps[i], NULL);

		RCU_INIT_POINTER(q->vlan, NULL);

			vlan->numvtaps--;

		}

	}

	BUG_ON(vlan->numvtaps != 0);

	/* guarantee that any future macvtap_set_queue will fail */

	vlan->numvtaps = MAX_MACVTAP_QUEUES;

	spin_unlock(&macvtap_lock);

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