[net-next,RFC,7/8] macvtap: add TUNSETQUEUE ioctl
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Message ID 1369278753-2533-8-git-send-email-jasowang@redhat.com
State New, archived
Headers show
Series
  • multiqueue API support for macvtap
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Commit Message

Jason Wang May 23, 2013, 3:12 a.m. UTC
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 by just introduce a pointer detached which was set when the queue
were detached. Only the queue with NULL set to this pointer can be used to
forward packets.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/macvtap.c      |  147 +++++++++++++++++++++++++++++++++++--------
 include/linux/if_macvlan.h |    7 ++
 2 files changed, 126 insertions(+), 28 deletions(-)

Comments

Michael S. Tsirkin May 23, 2013, 11:52 a.m. UTC | #1
On Thu, May 23, 2013 at 11:12:32AM +0800, Jason Wang wrote:
> 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 by just introduce a pointer detached which was set when the queue
> were detached. Only the queue with NULL set to this pointer can be used to
> forward packets.
> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Isn't this a bit too tricky?
Why keep disabled queues on the array at all?
Let's add a linked list of all queues for accounting.
Use array for enabled queues only, for data path.

> ---
>  drivers/net/macvtap.c      |  147 +++++++++++++++++++++++++++++++++++--------
>  include/linux/if_macvlan.h |    7 ++
>  2 files changed, 126 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index e3f9344..06b10a5 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -85,67 +85,131 @@ static const struct proto_ops macvtap_socket_ops;
>   */
>  static DEFINE_SPINLOCK(macvtap_lock);
>  
> +static void macvtap_swap_slot(struct macvlan_dev *vlan, int a, int b)
> +{
> +	struct macvtap_queue *q1, *q2;
> +
> +	if (a == b)
> +		return;
> +
> +	q1 = rcu_dereference_protected(vlan->taps[a],
> +				       lockdep_is_held(&macvtap_lock));
> +	q2 = rcu_dereference_protected(vlan->taps[b],
> +				       lockdep_is_held(&macvtap_lock));
> +
> +	BUG_ON(q1 == NULL || q2 == NULL);
> +
> +	rcu_assign_pointer(vlan->taps[a], vlan->taps[b]);
> +	rcu_assign_pointer(vlan->taps[b], q1);
> +
> +	q1->queue_index = b;
> +	q2->queue_index = a;
> +}
> +
>  static int macvtap_set_queue(struct net_device *dev, struct file *file,
> -				struct macvtap_queue *q)
> +			     struct macvtap_queue *q, bool enable)
>  {
>  	struct macvlan_dev *vlan = netdev_priv(dev);
>  	int err = -EBUSY;
> +	int total;
>  
>  	spin_lock(&macvtap_lock);
> -	if (vlan->numvtaps == MAX_MACVTAP_QUEUES)
> +
> +	total = vlan->numvtaps + vlan->numdisabled;
> +	if (!enable && total == MAX_MACVTAP_QUEUES)
> +		goto out;
> +
> +	err = -EINVAL;
> +	if (enable && q->queue_index < vlan->numvtaps)
>  		goto out;
>  
>  	err = 0;
> -	rcu_assign_pointer(q->vlan, vlan);
> -	rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);
> -	sock_hold(&q->sk);
>  
> -	q->file = file;
> -	q->queue_index = vlan->numvtaps;
> -	file->private_data = q;
> +	if (enable) {
> +		BUG_ON(q->queue_index >= total);
> +		macvtap_swap_slot(vlan, q->queue_index, vlan->numvtaps);
> +		--vlan->numdisabled;
> +	} else {
> +		rcu_assign_pointer(q->vlan, vlan);
> +		rcu_assign_pointer(vlan->taps[total], q);
> +		sock_hold(&q->sk);
> +
> +		q->file = file;
> +		q->queue_index = total;
> +		file->private_data = q;
> +		if (vlan->numdisabled)
> +			macvtap_swap_slot(vlan, vlan->numvtaps, total);
> +
> +		/* Make sure the pointers were seen before numvtaps. */
> +		smp_wmb();
> +	}
>  
>  	vlan->numvtaps++;
> -
>  out:
>  	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
> - * one from the macvlan_dev if that still exists.
> + * The file owning the queue got closed or disabled.
> + *
> + * If closed give up both the reference that the files holds as well as the
> + * one from the macvlan_dev if that still exists. If disabled, reshuffle the
> + * array of taps.
>   *
>   * Using the spinlock makes sure that we don't get
>   * to the queue again after destroying it.
>   */
> -static void macvtap_put_queue(struct macvtap_queue *q)
> +static int macvtap_put_queue(struct macvtap_queue *q, bool clean)

s/clean/release/
and add a comment explaining what it is.

>  {
> -	struct macvtap_queue *nq;
>  	struct macvlan_dev *vlan;
> +	int err = -EINVAL;
>  
>  	spin_lock(&macvtap_lock);
>  	vlan = rcu_dereference_protected(q->vlan,
>  					 lockdep_is_held(&macvtap_lock));
> +
>  	if (vlan) {
> +		int total = vlan->numvtaps + vlan->numdisabled;
>  		int index = q->queue_index;
> -		BUG_ON(index >= vlan->numvtaps);
> +		bool disabled = q->queue_index >= vlan->numvtaps;
>  
> -		rcu_assign_pointer(vlan->taps[index],
> -				   vlan->taps[vlan->numvtaps - 1]);
> -		RCU_INIT_POINTER(q->vlan, NULL);
> -		nq = rcu_dereference_protected(vlan->taps[index],
> -					       lockdep_is_held(&macvtap_lock));
> -		nq->queue_index = index;
> +		if (!clean) {
> +			BUG_ON(q->queue_index >= total);
> +			if (q->queue_index >= vlan->numvtaps)
> +				goto out;
> +		}
>  
> -		sock_put(&q->sk);
> -		--vlan->numvtaps;
> -	}
> +		err = 0;
> +		macvtap_swap_slot(vlan, index, total - 1);
> +		if (!disabled && vlan->numdisabled)

What's the logic here?

> +			macvtap_swap_slot(vlan, index, vlan->numvtaps - 1);

So these swaps do a lot of RCU assign, presumably we need
synchronize_rcu as well?

> +
> +		if (clean) {
> +			RCU_INIT_POINTER(vlan->taps[total - 1], NULL);
> +			RCU_INIT_POINTER(q->vlan, NULL);
> +			sock_put(&q->sk);
> +			if (disabled)
> +				--vlan->numdisabled;
> +			else
> +				--vlan->numvtaps;
> +		} else {
> +			--vlan->numvtaps;
> +			++vlan->numdisabled;
> +		}
> +
> +	} else if (clean)
> +		err = 0;
>  
> +out:
>  	spin_unlock(&macvtap_lock);
>  
>  	synchronize_rcu();
> -	sock_put(&q->sk);
> +
> +	if (clean)
> +		sock_put(&q->sk);
> +
> +	return err;
>  }
>  
>  /*
> @@ -201,7 +265,7 @@ static void macvtap_del_queues(struct net_device *dev)
>  
>  	/* macvtap_put_queue can free some slots, so go through all slots */
>  	spin_lock(&macvtap_lock);
> -	for (i = 0; i < vlan->numvtaps; i++) {
> +	for (i = 0; i < vlan->numvtaps + vlan->numdisabled; i++) {
>  		q = rcu_dereference_protected(vlan->taps[i],
>  					      lockdep_is_held(&macvtap_lock));
>  		BUG_ON(q == NULL);
> @@ -211,6 +275,7 @@ static void macvtap_del_queues(struct net_device *dev)
>  	}
>  	/* guarantee that any future macvtap_set_queue will fail */
>  	vlan->numvtaps = MAX_MACVTAP_QUEUES;
> +	vlan->numdisabled = 0;
>  	spin_unlock(&macvtap_lock);
>  
>  	synchronize_rcu();
> @@ -384,7 +449,7 @@ static int macvtap_open(struct inode *inode, struct file *file)
>  	if ((dev->features & NETIF_F_HIGHDMA) && (dev->features & NETIF_F_SG))
>  		sock_set_flag(&q->sk, SOCK_ZEROCOPY);
>  
> -	err = macvtap_set_queue(dev, file, q);
> +	err = macvtap_set_queue(dev, file, q, false);
>  	if (err)
>  		sock_put(&q->sk);
>  
> @@ -398,7 +463,7 @@ out:
>  static int macvtap_release(struct inode *inode, struct file *file)
>  {
>  	struct macvtap_queue *q = file->private_data;
> -	macvtap_put_queue(q);
> +	macvtap_put_queue(q, true);
>  	return 0;
>  }
>  
> @@ -922,6 +987,27 @@ static int macvtap_set_iff(struct file *file, struct ifreq __user *ifr_u)
>  	return 0;
>  }
>  
> +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 = -EINVAL;
> +
> +	vlan = macvtap_get_vlan(q);
> +	if (!vlan)
> +		goto done;
> +
> +	if (flags & IFF_ATTACH_QUEUE)
> +		ret = macvtap_set_queue(vlan->dev, file, q, true);
> +	else if (flags & IFF_DETACH_QUEUE)
> +		ret = macvtap_put_queue(q, false);
> +
> +	macvtap_put_vlan(vlan);
> +
> +done:
> +	return ret;
> +}
> +
>  /*
>   * provide compatibility with generic tun/tap interface
>   */
> @@ -954,6 +1040,11 @@ 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 32e943a..f134afb 100644
> --- a/include/linux/if_macvlan.h
> +++ b/include/linux/if_macvlan.h
> @@ -69,8 +69,15 @@ struct macvlan_dev {
>  	u16			flags;
>  	int (*receive)(struct sk_buff *skb);
>  	int (*forward)(struct net_device *dev, struct sk_buff *skb);
> +	/* This array tracks all taps (include disabled ones) and will be
> +	 * reshuffled to keep the following order:
> +	 * [0, numvtaps) : enabled taps,
> +	 * [numvtaps, numvtaps + numdisabled) : disabled taps,
> +	 * [numvtaps + numdisabled, MAX_MACVTAP_QUEUES) : unused slots
> +	 */
>  	struct macvtap_queue	*taps[MAX_MACVTAP_QUEUES];
>  	int			numvtaps;
> +	int			numdisabled;
>  	int			minor;
>  };
>  
> -- 
> 1.7.1
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Jason Wang May 24, 2013, 6:19 a.m. UTC | #2
On 05/23/2013 07:52 PM, Michael S. Tsirkin wrote:
> On Thu, May 23, 2013 at 11:12:32AM +0800, Jason Wang wrote:
>> 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 by just introduce a pointer detached which was set when the queue
>> were detached. Only the queue with NULL set to this pointer can be used to
>> forward packets.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
> Isn't this a bit too tricky?

Well, not tricky and it was just like what we did the reshuffling in
PATCH 5/8
> Why keep disabled queues on the array at all?

Both are ok, but this method need less data structures in macvlan_dev.
> Let's add a linked list of all queues for accounting.
> Use array for enabled queues only, for data path.

This would not be simpler than just do in place reshuffling.
>
>> ---
>>  drivers/net/macvtap.c      |  147 +++++++++++++++++++++++++++++++++++--------
>>  include/linux/if_macvlan.h |    7 ++
>>  2 files changed, 126 insertions(+), 28 deletions(-)
>>
>> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
>> index e3f9344..06b10a5 100644
>> --- a/drivers/net/macvtap.c
>> +++ b/drivers/net/macvtap.c
>> @@ -85,67 +85,131 @@ static const struct proto_ops macvtap_socket_ops;
>>   */
>>  static DEFINE_SPINLOCK(macvtap_lock);
>>  
>> +static void macvtap_swap_slot(struct macvlan_dev *vlan, int a, int b)
>> +{
>> +	struct macvtap_queue *q1, *q2;
>> +
>> +	if (a == b)
>> +		return;
>> +
>> +	q1 = rcu_dereference_protected(vlan->taps[a],
>> +				       lockdep_is_held(&macvtap_lock));
>> +	q2 = rcu_dereference_protected(vlan->taps[b],
>> +				       lockdep_is_held(&macvtap_lock));
>> +
>> +	BUG_ON(q1 == NULL || q2 == NULL);
>> +
>> +	rcu_assign_pointer(vlan->taps[a], vlan->taps[b]);
>> +	rcu_assign_pointer(vlan->taps[b], q1);
>> +
>> +	q1->queue_index = b;
>> +	q2->queue_index = a;
>> +}
>> +
>>  static int macvtap_set_queue(struct net_device *dev, struct file *file,
>> -				struct macvtap_queue *q)
>> +			     struct macvtap_queue *q, bool enable)
>>  {
>>  	struct macvlan_dev *vlan = netdev_priv(dev);
>>  	int err = -EBUSY;
>> +	int total;
>>  
>>  	spin_lock(&macvtap_lock);
>> -	if (vlan->numvtaps == MAX_MACVTAP_QUEUES)
>> +
>> +	total = vlan->numvtaps + vlan->numdisabled;
>> +	if (!enable && total == MAX_MACVTAP_QUEUES)
>> +		goto out;
>> +
>> +	err = -EINVAL;
>> +	if (enable && q->queue_index < vlan->numvtaps)
>>  		goto out;
>>  
>>  	err = 0;
>> -	rcu_assign_pointer(q->vlan, vlan);
>> -	rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);
>> -	sock_hold(&q->sk);
>>  
>> -	q->file = file;
>> -	q->queue_index = vlan->numvtaps;
>> -	file->private_data = q;
>> +	if (enable) {
>> +		BUG_ON(q->queue_index >= total);
>> +		macvtap_swap_slot(vlan, q->queue_index, vlan->numvtaps);
>> +		--vlan->numdisabled;
>> +	} else {
>> +		rcu_assign_pointer(q->vlan, vlan);
>> +		rcu_assign_pointer(vlan->taps[total], q);
>> +		sock_hold(&q->sk);
>> +
>> +		q->file = file;
>> +		q->queue_index = total;
>> +		file->private_data = q;
>> +		if (vlan->numdisabled)
>> +			macvtap_swap_slot(vlan, vlan->numvtaps, total);
>> +
>> +		/* Make sure the pointers were seen before numvtaps. */
>> +		smp_wmb();
>> +	}
>>  
>>  	vlan->numvtaps++;
>> -
>>  out:
>>  	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
>> - * one from the macvlan_dev if that still exists.
>> + * The file owning the queue got closed or disabled.
>> + *
>> + * If closed give up both the reference that the files holds as well as the
>> + * one from the macvlan_dev if that still exists. If disabled, reshuffle the
>> + * array of taps.
>>   *
>>   * Using the spinlock makes sure that we don't get
>>   * to the queue again after destroying it.
>>   */
>> -static void macvtap_put_queue(struct macvtap_queue *q)
>> +static int macvtap_put_queue(struct macvtap_queue *q, bool clean)
> s/clean/release/
> and add a comment explaining what it is.

Ok.
>>  {
>> -	struct macvtap_queue *nq;
>>  	struct macvlan_dev *vlan;
>> +	int err = -EINVAL;
>>  
>>  	spin_lock(&macvtap_lock);
>>  	vlan = rcu_dereference_protected(q->vlan,
>>  					 lockdep_is_held(&macvtap_lock));
>> +
>>  	if (vlan) {
>> +		int total = vlan->numvtaps + vlan->numdisabled;
>>  		int index = q->queue_index;
>> -		BUG_ON(index >= vlan->numvtaps);
>> +		bool disabled = q->queue_index >= vlan->numvtaps;
>>  
>> -		rcu_assign_pointer(vlan->taps[index],
>> -				   vlan->taps[vlan->numvtaps - 1]);
>> -		RCU_INIT_POINTER(q->vlan, NULL);
>> -		nq = rcu_dereference_protected(vlan->taps[index],
>> -					       lockdep_is_held(&macvtap_lock));
>> -		nq->queue_index = index;
>> +		if (!clean) {
>> +			BUG_ON(q->queue_index >= total);
>> +			if (q->queue_index >= vlan->numvtaps)
>> +				goto out;
>> +		}
>>  
>> -		sock_put(&q->sk);
>> -		--vlan->numvtaps;
>> -	}
>> +		err = 0;
>> +		macvtap_swap_slot(vlan, index, total - 1);
>> +		if (!disabled && vlan->numdisabled)
> What's the logic here?

If there's at least one disabled taps, the above swap will move a
disabled tap into enabled area. So we need to do swap it with the last
enabled tap to keep the right order.
>
>> +			macvtap_swap_slot(vlan, index, vlan->numvtaps - 1);
> So these swaps do a lot of RCU assign, presumably we need
> synchronize_rcu as well?

There is a synchronize_rcu() below, and we do the cleanup -sock_put()
after that. And since we purge the socket during its destruction, no
need to care about the little possibility that a packet were sent to the
disabled or removed queue.
>
>> +
>> +		if (clean) {
>> +			RCU_INIT_POINTER(vlan->taps[total - 1], NULL);
>> +			RCU_INIT_POINTER(q->vlan, NULL);
>> +			sock_put(&q->sk);
>> +			if (disabled)
>> +				--vlan->numdisabled;
>> +			else
>> +				--vlan->numvtaps;
>> +		} else {
>> +			--vlan->numvtaps;
>> +			++vlan->numdisabled;
>> +		}
>> +
>> +	} else if (clean)
>> +		err = 0;
>>  
>> +out:
>>  	spin_unlock(&macvtap_lock);
>>  
>>  	synchronize_rcu();
>> -	sock_put(&q->sk);
>> +
>> +	if (clean)
>> +		sock_put(&q->sk);
>> +
>> +	return err;
>>  }
>>  
>>  /*
>> @@ -201,7 +265,7 @@ static void macvtap_del_queues(struct net_device *dev)
>>  
>>  	/* macvtap_put_queue can free some slots, so go through all slots */
>>  	spin_lock(&macvtap_lock);
>> -	for (i = 0; i < vlan->numvtaps; i++) {
>> +	for (i = 0; i < vlan->numvtaps + vlan->numdisabled; i++) {
>>  		q = rcu_dereference_protected(vlan->taps[i],
>>  					      lockdep_is_held(&macvtap_lock));
>>  		BUG_ON(q == NULL);
>> @@ -211,6 +275,7 @@ static void macvtap_del_queues(struct net_device *dev)
>>  	}
>>  	/* guarantee that any future macvtap_set_queue will fail */
>>  	vlan->numvtaps = MAX_MACVTAP_QUEUES;
>> +	vlan->numdisabled = 0;
>>  	spin_unlock(&macvtap_lock);
>>  
>>  	synchronize_rcu();
>> @@ -384,7 +449,7 @@ static int macvtap_open(struct inode *inode, struct file *file)
>>  	if ((dev->features & NETIF_F_HIGHDMA) && (dev->features & NETIF_F_SG))
>>  		sock_set_flag(&q->sk, SOCK_ZEROCOPY);
>>  
>> -	err = macvtap_set_queue(dev, file, q);
>> +	err = macvtap_set_queue(dev, file, q, false);
>>  	if (err)
>>  		sock_put(&q->sk);
>>  
>> @@ -398,7 +463,7 @@ out:
>>  static int macvtap_release(struct inode *inode, struct file *file)
>>  {
>>  	struct macvtap_queue *q = file->private_data;
>> -	macvtap_put_queue(q);
>> +	macvtap_put_queue(q, true);
>>  	return 0;
>>  }
>>  
>> @@ -922,6 +987,27 @@ static int macvtap_set_iff(struct file *file, struct ifreq __user *ifr_u)
>>  	return 0;
>>  }
>>  
>> +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 = -EINVAL;
>> +
>> +	vlan = macvtap_get_vlan(q);
>> +	if (!vlan)
>> +		goto done;
>> +
>> +	if (flags & IFF_ATTACH_QUEUE)
>> +		ret = macvtap_set_queue(vlan->dev, file, q, true);
>> +	else if (flags & IFF_DETACH_QUEUE)
>> +		ret = macvtap_put_queue(q, false);
>> +
>> +	macvtap_put_vlan(vlan);
>> +
>> +done:
>> +	return ret;
>> +}
>> +
>>  /*
>>   * provide compatibility with generic tun/tap interface
>>   */
>> @@ -954,6 +1040,11 @@ 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 32e943a..f134afb 100644
>> --- a/include/linux/if_macvlan.h
>> +++ b/include/linux/if_macvlan.h
>> @@ -69,8 +69,15 @@ struct macvlan_dev {
>>  	u16			flags;
>>  	int (*receive)(struct sk_buff *skb);
>>  	int (*forward)(struct net_device *dev, struct sk_buff *skb);
>> +	/* This array tracks all taps (include disabled ones) and will be
>> +	 * reshuffled to keep the following order:
>> +	 * [0, numvtaps) : enabled taps,
>> +	 * [numvtaps, numvtaps + numdisabled) : disabled taps,
>> +	 * [numvtaps + numdisabled, MAX_MACVTAP_QUEUES) : unused slots
>> +	 */
>>  	struct macvtap_queue	*taps[MAX_MACVTAP_QUEUES];
>>  	int			numvtaps;
>> +	int			numdisabled;
>>  	int			minor;
>>  };
>>  
>> -- 
>> 1.7.1

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Patch
diff mbox series

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index e3f9344..06b10a5 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -85,67 +85,131 @@  static const struct proto_ops macvtap_socket_ops;
  */
 static DEFINE_SPINLOCK(macvtap_lock);
 
+static void macvtap_swap_slot(struct macvlan_dev *vlan, int a, int b)
+{
+	struct macvtap_queue *q1, *q2;
+
+	if (a == b)
+		return;
+
+	q1 = rcu_dereference_protected(vlan->taps[a],
+				       lockdep_is_held(&macvtap_lock));
+	q2 = rcu_dereference_protected(vlan->taps[b],
+				       lockdep_is_held(&macvtap_lock));
+
+	BUG_ON(q1 == NULL || q2 == NULL);
+
+	rcu_assign_pointer(vlan->taps[a], vlan->taps[b]);
+	rcu_assign_pointer(vlan->taps[b], q1);
+
+	q1->queue_index = b;
+	q2->queue_index = a;
+}
+
 static int macvtap_set_queue(struct net_device *dev, struct file *file,
-				struct macvtap_queue *q)
+			     struct macvtap_queue *q, bool enable)
 {
 	struct macvlan_dev *vlan = netdev_priv(dev);
 	int err = -EBUSY;
+	int total;
 
 	spin_lock(&macvtap_lock);
-	if (vlan->numvtaps == MAX_MACVTAP_QUEUES)
+
+	total = vlan->numvtaps + vlan->numdisabled;
+	if (!enable && total == MAX_MACVTAP_QUEUES)
+		goto out;
+
+	err = -EINVAL;
+	if (enable && q->queue_index < vlan->numvtaps)
 		goto out;
 
 	err = 0;
-	rcu_assign_pointer(q->vlan, vlan);
-	rcu_assign_pointer(vlan->taps[vlan->numvtaps], q);
-	sock_hold(&q->sk);
 
-	q->file = file;
-	q->queue_index = vlan->numvtaps;
-	file->private_data = q;
+	if (enable) {
+		BUG_ON(q->queue_index >= total);
+		macvtap_swap_slot(vlan, q->queue_index, vlan->numvtaps);
+		--vlan->numdisabled;
+	} else {
+		rcu_assign_pointer(q->vlan, vlan);
+		rcu_assign_pointer(vlan->taps[total], q);
+		sock_hold(&q->sk);
+
+		q->file = file;
+		q->queue_index = total;
+		file->private_data = q;
+		if (vlan->numdisabled)
+			macvtap_swap_slot(vlan, vlan->numvtaps, total);
+
+		/* Make sure the pointers were seen before numvtaps. */
+		smp_wmb();
+	}
 
 	vlan->numvtaps++;
-
 out:
 	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
- * one from the macvlan_dev if that still exists.
+ * The file owning the queue got closed or disabled.
+ *
+ * If closed give up both the reference that the files holds as well as the
+ * one from the macvlan_dev if that still exists. If disabled, reshuffle the
+ * array of taps.
  *
  * Using the spinlock makes sure that we don't get
  * to the queue again after destroying it.
  */
-static void macvtap_put_queue(struct macvtap_queue *q)
+static int macvtap_put_queue(struct macvtap_queue *q, bool clean)
 {
-	struct macvtap_queue *nq;
 	struct macvlan_dev *vlan;
+	int err = -EINVAL;
 
 	spin_lock(&macvtap_lock);
 	vlan = rcu_dereference_protected(q->vlan,
 					 lockdep_is_held(&macvtap_lock));
+
 	if (vlan) {
+		int total = vlan->numvtaps + vlan->numdisabled;
 		int index = q->queue_index;
-		BUG_ON(index >= vlan->numvtaps);
+		bool disabled = q->queue_index >= vlan->numvtaps;
 
-		rcu_assign_pointer(vlan->taps[index],
-				   vlan->taps[vlan->numvtaps - 1]);
-		RCU_INIT_POINTER(q->vlan, NULL);
-		nq = rcu_dereference_protected(vlan->taps[index],
-					       lockdep_is_held(&macvtap_lock));
-		nq->queue_index = index;
+		if (!clean) {
+			BUG_ON(q->queue_index >= total);
+			if (q->queue_index >= vlan->numvtaps)
+				goto out;
+		}
 
-		sock_put(&q->sk);
-		--vlan->numvtaps;
-	}
+		err = 0;
+		macvtap_swap_slot(vlan, index, total - 1);
+		if (!disabled && vlan->numdisabled)
+			macvtap_swap_slot(vlan, index, vlan->numvtaps - 1);
+
+		if (clean) {
+			RCU_INIT_POINTER(vlan->taps[total - 1], NULL);
+			RCU_INIT_POINTER(q->vlan, NULL);
+			sock_put(&q->sk);
+			if (disabled)
+				--vlan->numdisabled;
+			else
+				--vlan->numvtaps;
+		} else {
+			--vlan->numvtaps;
+			++vlan->numdisabled;
+		}
+
+	} else if (clean)
+		err = 0;
 
+out:
 	spin_unlock(&macvtap_lock);
 
 	synchronize_rcu();
-	sock_put(&q->sk);
+
+	if (clean)
+		sock_put(&q->sk);
+
+	return err;
 }
 
 /*
@@ -201,7 +265,7 @@  static void macvtap_del_queues(struct net_device *dev)
 
 	/* macvtap_put_queue can free some slots, so go through all slots */
 	spin_lock(&macvtap_lock);
-	for (i = 0; i < vlan->numvtaps; i++) {
+	for (i = 0; i < vlan->numvtaps + vlan->numdisabled; i++) {
 		q = rcu_dereference_protected(vlan->taps[i],
 					      lockdep_is_held(&macvtap_lock));
 		BUG_ON(q == NULL);
@@ -211,6 +275,7 @@  static void macvtap_del_queues(struct net_device *dev)
 	}
 	/* guarantee that any future macvtap_set_queue will fail */
 	vlan->numvtaps = MAX_MACVTAP_QUEUES;
+	vlan->numdisabled = 0;
 	spin_unlock(&macvtap_lock);
 
 	synchronize_rcu();
@@ -384,7 +449,7 @@  static int macvtap_open(struct inode *inode, struct file *file)
 	if ((dev->features & NETIF_F_HIGHDMA) && (dev->features & NETIF_F_SG))
 		sock_set_flag(&q->sk, SOCK_ZEROCOPY);
 
-	err = macvtap_set_queue(dev, file, q);
+	err = macvtap_set_queue(dev, file, q, false);
 	if (err)
 		sock_put(&q->sk);
 
@@ -398,7 +463,7 @@  out:
 static int macvtap_release(struct inode *inode, struct file *file)
 {
 	struct macvtap_queue *q = file->private_data;
-	macvtap_put_queue(q);
+	macvtap_put_queue(q, true);
 	return 0;
 }
 
@@ -922,6 +987,27 @@  static int macvtap_set_iff(struct file *file, struct ifreq __user *ifr_u)
 	return 0;
 }
 
+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 = -EINVAL;
+
+	vlan = macvtap_get_vlan(q);
+	if (!vlan)
+		goto done;
+
+	if (flags & IFF_ATTACH_QUEUE)
+		ret = macvtap_set_queue(vlan->dev, file, q, true);
+	else if (flags & IFF_DETACH_QUEUE)
+		ret = macvtap_put_queue(q, false);
+
+	macvtap_put_vlan(vlan);
+
+done:
+	return ret;
+}
+
 /*
  * provide compatibility with generic tun/tap interface
  */
@@ -954,6 +1040,11 @@  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 32e943a..f134afb 100644
--- a/include/linux/if_macvlan.h
+++ b/include/linux/if_macvlan.h
@@ -69,8 +69,15 @@  struct macvlan_dev {
 	u16			flags;
 	int (*receive)(struct sk_buff *skb);
 	int (*forward)(struct net_device *dev, struct sk_buff *skb);
+	/* This array tracks all taps (include disabled ones) and will be
+	 * reshuffled to keep the following order:
+	 * [0, numvtaps) : enabled taps,
+	 * [numvtaps, numvtaps + numdisabled) : disabled taps,
+	 * [numvtaps + numdisabled, MAX_MACVTAP_QUEUES) : unused slots
+	 */
 	struct macvtap_queue	*taps[MAX_MACVTAP_QUEUES];
 	int			numvtaps;
+	int			numdisabled;
 	int			minor;
 };