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>

1 files changed, 116 insertions, 19 deletions

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 5ccba99b15f4..d2d1d5578b61 100644
--- 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;