Messages in this thread | | | Date | Wed, 5 Jun 2013 13:59:28 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [net-next rfc V3 8/9] macvtap: add TUNSETQUEUE ioctl |
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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@redhat.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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