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macvtap: eliminate linear search

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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: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2013-06-05 23:54:38 +00:00 committed by David S. Miller
parent f0afce01aa
commit 376b1aabe1
1 changed files with 20 additions and 44 deletions
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64
drivers/net/macvtap.c
View File

@ -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;
@ -182,8 +170,7 @@ 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;
goto out;
}
if (likely(skb_rx_queue_recorded(skb))) {
@ -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;
goto out;
}
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) {
qlist[j++] = q;
RCU_INIT_POINTER(vlan->taps[i], NULL);
RCU_INIT_POINTER(q->vlan, NULL);
vlan->numvtaps--;
}
BUG_ON(q == NULL);
qlist[j++] = q;
RCU_INIT_POINTER(vlan->taps[i], NULL);
RCU_INIT_POINTER(q->vlan, NULL);
}
BUG_ON(vlan->numvtaps != 0);
/* guarantee that any future macvtap_set_queue will fail */
vlan->numvtaps = MAX_MACVTAP_QUEUES;
spin_unlock(&macvtap_lock);