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Message-ID: <20130605105928.GH31830@redhat.com>
Date: Wed, 5 Jun 2013 13:59:28 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, sergei.shtylyov@...entembedded.com
Subject: Re: [net-next rfc V3 8/9] macvtap: add TUNSETQUEUE ioctl
On Wed, Jun 05, 2013 at 02:36:31PM +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 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@...hat.com>
> ---
> drivers/net/macvtap.c | 133 +++++++++++++++++++++++++++++++++++++++-----
> include/linux/if_macvlan.h | 4 +
> 2 files changed, 122 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index 14764cc..355e6ad 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 +87,37 @@ 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++;
> + vlan->numdisabled--;
> +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->numvtaps + vlan->numdisabled == MAX_MACVTAP_QUEUES)
> goto out;
>
> err = 0;
> @@ -102,7 +127,9 @@ 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->tap_link);
>
> vlan->numvtaps++;
>
> @@ -111,6 +138,38 @@ out:
> return err;
> }
>
> +static int macvtap_disable_queue(struct macvtap_queue *q)
> +{
> + struct macvlan_dev *vlan;
> + struct macvtap_queue *nq;
> + int err = 0;
> +
> + spin_lock(&macvtap_lock);
> + vlan = rcu_dereference_protected(q->vlan,
> + lockdep_is_held(&macvtap_lock));
> +
> + if (!q->enabled) {
> + err = -EINVAL;
> + goto out;
> + }
> +
> + if (vlan) {
> + int index = q->queue_index;
> + 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--;
> + vlan->numdisabled++;
> + }
> +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
> @@ -128,18 +187,24 @@ static void macvtap_put_queue(struct macvtap_queue *q)
> vlan = rcu_dereference_protected(q->vlan,
> lockdep_is_held(&macvtap_lock));
> if (vlan) {
> + int numvtaps = vlan->numvtaps;
> 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(index >= vlan->numvtaps);
> + nq = rcu_dereference_protected(vlan->taps[numvtaps - 1],
> + lockdep_is_held(&macvtap_lock));
> + rcu_assign_pointer(vlan->taps[index], nq);
Do we really need these tricks?
Can't we call macvtap_disable_queue and then only handle disable queues
here?
> + nq->queue_index = index;
> +
> + RCU_INIT_POINTER(vlan->taps[numvtaps - 1], NULL);
> + vlan->numvtaps--;
> + } else
> + vlan->numdisabled--;
>
> - RCU_INIT_POINTER(vlan->taps[vlan->numvtaps - 1], NULL);
> RCU_INIT_POINTER(q->vlan, NULL);
> sock_put(&q->sk);
> - --vlan->numvtaps;
> + list_del_init(&q->next);
> }
>
> spin_unlock(&macvtap_lock);
> @@ -160,6 +225,10 @@ static struct macvtap_queue *macvtap_get_queue(struct net_device *dev,
> {
> struct macvlan_dev *vlan = netdev_priv(dev);
> struct macvtap_queue *tap = NULL;
> + /* numvtaps here is just a hint, even if the number of active taps were
> + * reduced in the same sime,
typo
> since we are protected by rcu read lock,
> + * we're safe here.
I don't really understand what is this comment trying to say.
What is protected? What is safe? safe time as what?
> + */
> int numvtaps = ACCESS_ONCE(vlan->numvtaps);
> __u32 rxq;
>
> @@ -196,20 +265,25 @@ 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->tap_link, 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--;
> + else
> + vlan->numdisabled--;
> }
> + for (i = 0; i < vlan->numvtaps; i++)
> + RCU_INIT_POINTER(vlan->taps[i], NULL);
> + BUG_ON(vlan->numvtaps + vlan->numdisabled != 0);
Better two BUG_ON checks - they are both 0 right?
And no need for != 0.
> /* guarantee that any future macvtap_set_queue will fail */
> vlan->numvtaps = MAX_MACVTAP_QUEUES;
> + vlan->numdisabled = 0;
What's this doing? We know it's 0 ...
> spin_unlock(&macvtap_lock);
>
> synchronize_rcu();
> @@ -298,6 +372,9 @@ 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->tap_link);
> +
> /* Don't put anything that may fail after macvlan_common_newlink
> * because we can't undo what it does.
> */
> @@ -926,6 +1003,27 @@ 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;
Can be just return -EINVAL, and you won't need to initialize
above.
> +
> + 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);
> +
> +done:
> + return ret;
> +}
> +
> /*
> * provide compatibility with generic tun/tap interface
> */
> @@ -958,6 +1056,11 @@ 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..87b9091 100644
> --- 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 tap_link;
Bad name, e.g. queue_list would be better.
> int numvtaps;
> + int numdisabled;
So numvtaps is number of entries in the taps array.
But to get items on list, you must add numdisabled and
numvtaps, that's confusing.
Instead of numdisabled, let's add a counter for
number of entries in the tap_link list.
How about numqueues?
> int minor;
> };
>
> --
> 1.7.1
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