macvtap: Implement multiqueue for macvtap driver

Implement multiqueue facility for macvtap driver. The idea is that
a macvtap device can be opened multiple times and the fd's can be
used to register eg, as backend for vhost.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 3b1c54a..4256727 100644 (file)
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -84,26 +84,45 @@ static const struct proto_ops macvtap_socket_ops;
 static DEFINE_SPINLOCK(macvtap_lock);
 
 /*
- * Choose the next free queue, for now there is only one
+ * 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(vlan->taps[i]) == 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);
-       if (rcu_dereference(vlan->tap))
+       if (vlan->numvtaps == MAX_MACVTAP_QUEUES)
                goto out;
 
        err = 0;
+       index = get_slot(vlan, NULL);
        rcu_assign_pointer(q->vlan, vlan);
-       rcu_assign_pointer(vlan->tap, q);
+       rcu_assign_pointer(vlan->taps[index], q);
        sock_hold(&q->sk);
 
        q->file = file;
        file->private_data = q;
 
+       vlan->numvtaps++;
+
 out:
        spin_unlock(&macvtap_lock);
        return err;
@@ -124,9 +143,12 @@ static void macvtap_put_queue(struct macvtap_queue *q)
        spin_lock(&macvtap_lock);
        vlan = rcu_dereference(q->vlan);
        if (vlan) {
-               rcu_assign_pointer(vlan->tap, NULL);
+               int index = get_slot(vlan, q);
+
+               rcu_assign_pointer(vlan->taps[index], NULL);
                rcu_assign_pointer(q->vlan, NULL);
                sock_put(&q->sk);
+               --vlan->numvtaps;
        }
 
        spin_unlock(&macvtap_lock);
@@ -136,39 +158,82 @@ static void macvtap_put_queue(struct macvtap_queue *q)
 }
 
 /*
- * Since we only support one queue, just dereference the pointer.
+ * Select a queue based on the rxq of the device on which this packet
+ * arrived. If the incoming device is not mq, calculate a flow hash
+ * to select a queue. If all fails, find the first available queue.
+ * Cache vlan->numvtaps since it can become zero during the execution
+ * of this function.
  */
 static struct macvtap_queue *macvtap_get_queue(struct net_device *dev,
                                               struct sk_buff *skb)
 {
        struct macvlan_dev *vlan = netdev_priv(dev);
+       struct macvtap_queue *tap = NULL;
+       int numvtaps = vlan->numvtaps;
+       __u32 rxq;
+
+       if (!numvtaps)
+               goto out;
+
+       if (likely(skb_rx_queue_recorded(skb))) {
+               rxq = skb_get_rx_queue(skb);
+
+               while (unlikely(rxq >= numvtaps))
+                       rxq -= numvtaps;
+
+               tap = rcu_dereference(vlan->taps[rxq]);
+               if (tap)
+                       goto out;
+       }
+
+       /* Check if we can use flow to select a queue */
+       rxq = skb_get_rxhash(skb);
+       if (rxq) {
+               tap = rcu_dereference(vlan->taps[rxq % numvtaps]);
+               if (tap)
+                       goto out;
+       }
 
-       return rcu_dereference(vlan->tap);
+       /* Everything failed - find first available queue */
+       for (rxq = 0; rxq < MAX_MACVTAP_QUEUES; rxq++) {
+               tap = rcu_dereference(vlan->taps[rxq]);
+               if (tap)
+                       break;
+       }
+
+out:
+       return tap;
 }
 
 /*
  * The net_device is going away, give up the reference
- * that it holds on the queue (all the queues one day)
- * and safely set the pointer from the queues to NULL.
+ * that it holds on all queues and safely set the pointer
+ * from the queues to NULL.
  */
 static void macvtap_del_queues(struct net_device *dev)
 {
        struct macvlan_dev *vlan = netdev_priv(dev);
-       struct macvtap_queue *q;
+       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);
-       q = rcu_dereference(vlan->tap);
-       if (!q) {
-               spin_unlock(&macvtap_lock);
-               return;
+       for (i = 0; i < MAX_MACVTAP_QUEUES && vlan->numvtaps; i++) {
+               q = rcu_dereference(vlan->taps[i]);
+               if (q) {
+                       qlist[j++] = q;
+                       rcu_assign_pointer(vlan->taps[i], NULL);
+                       rcu_assign_pointer(q->vlan, NULL);
+                       vlan->numvtaps--;
+               }
        }
-
-       rcu_assign_pointer(vlan->tap, NULL);
-       rcu_assign_pointer(q->vlan, NULL);
+       BUG_ON(vlan->numvtaps != 0);
        spin_unlock(&macvtap_lock);
 
        synchronize_rcu();
-       sock_put(&q->sk);
+
+       for (--j; j >= 0; j--)
+               sock_put(&qlist[j]->sk);
 }
 
 /*

diff --git a/include/linux/if_macvlan.h b/include/linux/if_macvlan.h
index 35280b3..8a2fd66 100644 (file)
--- a/include/linux/if_macvlan.h
+++ b/include/linux/if_macvlan.h
@@ -40,6 +40,12 @@ struct macvlan_rx_stats {
        unsigned long           rx_errors;
 };
 
+/*
+ * Maximum times a macvtap device can be opened. This can be used to
+ * configure the number of receive queue, e.g. for multiqueue virtio.
+ */
+#define MAX_MACVTAP_QUEUES     (NR_CPUS < 16 ? NR_CPUS : 16)
+
 struct macvlan_dev {
        struct net_device       *dev;
        struct list_head        list;
@@ -50,7 +56,8 @@ struct macvlan_dev {
        enum macvlan_mode       mode;
        int (*receive)(struct sk_buff *skb);
        int (*forward)(struct net_device *dev, struct sk_buff *skb);
-       struct macvtap_queue    *tap;
+       struct macvtap_queue    *taps[MAX_MACVTAP_QUEUES];
+       int                     numvtaps;
 };
 
 static inline void macvlan_count_rx(const struct macvlan_dev *vlan,