macvtap: add TUNSETQUEUE ioctl

This patch adds TUNSETQUEUE ioctl to let userspace can temporarily disable or
enable a queue of macvtap. This is used to be compatible at API layer of tuntap
to simplify the userspace to manage the queues. This is done through introducing
a linked list to track all taps while using vlan->taps array to only track
active taps.

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>

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 5ccba99..d2d1d55 100644 (file)
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -45,6 +45,8 @@ struct macvtap_queue {
        struct file *file;
        unsigned int flags;
        u16 queue_index;
+       bool enabled;
+       struct list_head next;
 };
 
 static struct proto macvtap_proto = {
@@ -85,14 +87,36 @@ static const struct proto_ops macvtap_socket_ops;
  */
 static DEFINE_SPINLOCK(macvtap_lock);
 
-static int macvtap_set_queue(struct net_device *dev, struct file *file,
+static int macvtap_enable_queue(struct net_device *dev, struct file *file,
                                struct macvtap_queue *q)
 {
        struct macvlan_dev *vlan = netdev_priv(dev);
+       int err = -EINVAL;
+
+       spin_lock(&macvtap_lock);
+
+       if (q->enabled)
+               goto out;
+
+       err = 0;
+       rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);
+       q->queue_index = vlan->numvtaps;
+       q->enabled = true;
+
+       vlan->numvtaps++;
+out:
+       spin_unlock(&macvtap_lock);
+       return err;
+}
+
+static int macvtap_set_queue(struct net_device *dev, struct file *file,
+                            struct macvtap_queue *q)
+{
+       struct macvlan_dev *vlan = netdev_priv(dev);
        int err = -EBUSY;
 
        spin_lock(&macvtap_lock);
-       if (vlan->numvtaps == MAX_MACVTAP_QUEUES)
+       if (vlan->numqueues == MAX_MACVTAP_QUEUES)
                goto out;
 
        err = 0;
@@ -102,15 +126,57 @@ static int macvtap_set_queue(struct net_device *dev, struct file *file,
 
        q->file = file;
        q->queue_index = vlan->numvtaps;
+       q->enabled = true;
        file->private_data = q;
+       list_add_tail(&q->next, &vlan->queue_list);
 
        vlan->numvtaps++;
+       vlan->numqueues++;
 
 out:
        spin_unlock(&macvtap_lock);
        return err;
 }
 
+static int __macvtap_disable_queue(struct macvtap_queue *q)
+{
+       struct macvlan_dev *vlan;
+       struct macvtap_queue *nq;
+
+       vlan = rcu_dereference_protected(q->vlan,
+                                        lockdep_is_held(&macvtap_lock));
+
+       if (!q->enabled)
+               return -EINVAL;
+
+       if (vlan) {
+               int index = q->queue_index;
+               BUG_ON(index >= vlan->numvtaps);
+               nq = rcu_dereference_protected(vlan->taps[vlan->numvtaps - 1],
+                                              lockdep_is_held(&macvtap_lock));
+               nq->queue_index = index;
+
+               rcu_assign_pointer(vlan->taps[index], nq);
+               RCU_INIT_POINTER(vlan->taps[vlan->numvtaps - 1], NULL);
+               q->enabled = false;
+
+               vlan->numvtaps--;
+       }
+
+       return 0;
+}
+
+static int macvtap_disable_queue(struct macvtap_queue *q)
+{
+       int err;
+
+       spin_lock(&macvtap_lock);
+       err = __macvtap_disable_queue(q);
+       spin_unlock(&macvtap_lock);
+
+       return err;
+}
+
 /*
  * The file owning the queue got closed, give up both
  * the reference that the files holds as well as the
@@ -121,25 +187,19 @@ 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 = q->queue_index;
-               BUG_ON(index >= vlan->numvtaps);
-
-               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;
+               if (q->enabled)
+                       BUG_ON(__macvtap_disable_queue(q));
 
-               RCU_INIT_POINTER(vlan->taps[vlan->numvtaps - 1], NULL);
+               vlan->numqueues--;
                RCU_INIT_POINTER(q->vlan, NULL);
                sock_put(&q->sk);
-               --vlan->numvtaps;
+               list_del_init(&q->next);
        }
 
        spin_unlock(&macvtap_lock);
@@ -160,6 +220,11 @@ static struct macvtap_queue *macvtap_get_queue(struct net_device *dev,
 {
        struct macvlan_dev *vlan = netdev_priv(dev);
        struct macvtap_queue *tap = NULL;
+       /* Access to taps array is protected by rcu, but access to numvtaps
+        * isn't. Below we use it to lookup a queue, but treat it as a hint
+        * and validate that the result isn't NULL - in case we are
+        * racing against queue removal.
+        */
        int numvtaps = ACCESS_ONCE(vlan->numvtaps);
        __u32 rxq;
 
@@ -196,18 +261,22 @@ out:
 static void macvtap_del_queues(struct net_device *dev)
 {
        struct macvlan_dev *vlan = netdev_priv(dev);
-       struct macvtap_queue *q, *qlist[MAX_MACVTAP_QUEUES];
+       struct macvtap_queue *q, *tmp, *qlist[MAX_MACVTAP_QUEUES];
        int i, j = 0;
 
        spin_lock(&macvtap_lock);
-       for (i = 0; i < vlan->numvtaps; i++) {
-               q = rcu_dereference_protected(vlan->taps[i],
-                                             lockdep_is_held(&macvtap_lock));
-               BUG_ON(q == NULL);
+       list_for_each_entry_safe(q, tmp, &vlan->queue_list, next) {
+               list_del_init(&q->next);
                qlist[j++] = q;
-               RCU_INIT_POINTER(vlan->taps[i], NULL);
                RCU_INIT_POINTER(q->vlan, NULL);
+               if (q->enabled)
+                       vlan->numvtaps--;
+               vlan->numqueues--;
        }
+       for (i = 0; i < vlan->numvtaps; i++)
+               RCU_INIT_POINTER(vlan->taps[i], NULL);
+       BUG_ON(vlan->numvtaps);
+       BUG_ON(vlan->numqueues);
        /* guarantee that any future macvtap_set_queue will fail */
        vlan->numvtaps = MAX_MACVTAP_QUEUES;
        spin_unlock(&macvtap_lock);
@@ -298,6 +367,9 @@ static int macvtap_newlink(struct net *src_net,
                           struct nlattr *tb[],
                           struct nlattr *data[])
 {
+       struct macvlan_dev *vlan = netdev_priv(dev);
+       INIT_LIST_HEAD(&vlan->queue_list);
+
        /* Don't put anything that may fail after macvlan_common_newlink
         * because we can't undo what it does.
         */
@@ -887,6 +959,25 @@ static void macvtap_put_vlan(struct macvlan_dev *vlan)
        dev_put(vlan->dev);
 }
 
+static int macvtap_ioctl_set_queue(struct file *file, unsigned int flags)
+{
+       struct macvtap_queue *q = file->private_data;
+       struct macvlan_dev *vlan;
+       int ret;
+
+       vlan = macvtap_get_vlan(q);
+       if (!vlan)
+               return -EINVAL;
+
+       if (flags & IFF_ATTACH_QUEUE)
+               ret = macvtap_enable_queue(vlan->dev, file, q);
+       else if (flags & IFF_DETACH_QUEUE)
+               ret = macvtap_disable_queue(q);
+
+       macvtap_put_vlan(vlan);
+       return ret;
+}
+
 /*
  * provide compatibility with generic tun/tap interface
  */
@@ -910,7 +1001,8 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
                        return -EFAULT;
 
                ret = 0;
-               if ((u & ~IFF_VNET_HDR) != (IFF_NO_PI | IFF_TAP))
+               if ((u & ~(IFF_VNET_HDR | IFF_MULTI_QUEUE)) !=
+                   (IFF_NO_PI | IFF_TAP))
                        ret = -EINVAL;
                else
                        q->flags = u;
@@ -929,6 +1021,11 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
                macvtap_put_vlan(vlan);
                return ret;
 
+       case TUNSETQUEUE:
+               if (get_user(u, &ifr->ifr_flags))
+                       return -EFAULT;
+               return macvtap_ioctl_set_queue(file, u);
+
        case TUNGETFEATURES:
                if (put_user(IFF_TAP | IFF_NO_PI | IFF_VNET_HDR, up))
                        return -EFAULT;

diff --git a/include/linux/if_macvlan.h b/include/linux/if_macvlan.h
index 62d8bda..1912133 100644 (file)
--- a/include/linux/if_macvlan.h
+++ b/include/linux/if_macvlan.h
@@ -69,8 +69,12 @@ struct macvlan_dev {
        u16                     flags;
        int (*receive)(struct sk_buff *skb);
        int (*forward)(struct net_device *dev, struct sk_buff *skb);
+       /* This array tracks active taps. */
        struct macvtap_queue    *taps[MAX_MACVTAP_QUEUES];
+       /* This list tracks all taps (both enabled and disabled) */
+       struct list_head        queue_list;
        int                     numvtaps;
+       int                     numqueues;
        int                     minor;
 };