On Mon, Jan 28, 2013 at 07:05:19PM +0800, Jason Wang wrote:
> We forbid polling, writing and reading when the file were detached, this may
> complex the user in several cases:
>
> - when guest pass some buffers to vhost/qemu and then disable some queues,
> host/qemu needs to do its own cleanup on those buffers which is complex
> sometimes. We can do this simply by allowing a user can still write to an
> disabled queue. Write to an disabled queue will cause the packet pass to the
> kernel and read will get nothing.
> - align the polling behavior with macvtap which never fails when the queue is
> created. This can simplify the polling errors handling of its user (e.g
> vhost)
>
> We can simply achieve this by don't assign NULL to tfile->tun when detached.
>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> drivers/net/tun.c | 25 ++++++++++++++++---------
> 1 files changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 30a7d0e..2fb19da 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -298,11 +298,12 @@ static void tun_flow_cleanup(unsigned long data)
> }
>
> static void tun_flow_update(struct tun_struct *tun, u32 rxhash,
> - u16 queue_index)
> + struct tun_file *tfile)
> {
> struct hlist_head *head;
> struct tun_flow_entry *e;
> unsigned long delay = tun->ageing_time;
> + u16 queue_index = tfile->queue_index;
>
> if (!rxhash)
> return;
> @@ -311,7 +312,9 @@ static void tun_flow_update(struct tun_struct *tun, u32
> rxhash,
>
> rcu_read_lock();
>
> - if (tun->numqueues == 1)
> + /* We may get a very small possibility of OOO during switching, not
> + * worth to optimize.*/
> + if (tun->numqueues == 1 || tfile->detached)
> goto unlock;
>
> e = tun_flow_find(head, rxhash);
> @@ -411,21 +414,21 @@ static void __tun_detach(struct tun_file *tfile, bool
> clean)
>
> tun = rtnl_dereference(tfile->tun);
>
> - if (tun) {
> + if (tun && !tfile->detached) {
> u16 index = tfile->queue_index;
> BUG_ON(index >= tun->numqueues);
> dev = tun->dev;
>
> rcu_assign_pointer(tun->tfiles[index],
> tun->tfiles[tun->numqueues - 1]);
> - rcu_assign_pointer(tfile->tun, NULL);
> ntfile = rtnl_dereference(tun->tfiles[index]);
> ntfile->queue_index = index;
>
> --tun->numqueues;
> - if (clean)
> + if (clean) {
> + rcu_assign_pointer(tfile->tun, NULL);
> sock_put(&tfile->sk);
> - else
> + } else
> tun_disable_queue(tun, tfile);
>
> synchronize_net();
> @@ -473,6 +476,10 @@ static void tun_detach_all(struct net_device *dev)
> rcu_assign_pointer(tfile->tun, NULL);
> --tun->numqueues;
> }
> + list_for_each_entry(tfile, &tun->disabled, next) {
> + wake_up_all(&tfile->wq.wait);
> + rcu_assign_pointer(tfile->tun, NULL);
> + }
> BUG_ON(tun->numqueues != 0);
>
> synchronize_net();
> @@ -503,7 +510,7 @@ static int tun_attach(struct tun_struct *tun, struct file
> *file)
> goto out;
>
> err = -EINVAL;
> - if (rtnl_dereference(tfile->tun))
> + if (rtnl_dereference(tfile->tun) && !tfile->detached)
> goto out;
>
> err = -EBUSY;
> @@ -1202,7 +1209,7 @@ static ssize_t tun_get_user(struct tun_struct *tun,
> struct tun_file *tfile,
> tun->dev->stats.rx_packets++;
> tun->dev->stats.rx_bytes += len;
>
> - tun_flow_update(tun, rxhash, tfile->queue_index);
> + tun_flow_update(tun, rxhash, tfile);
> return total_len;
> }
>
> @@ -1816,7 +1823,7 @@ static int tun_set_queue(struct file *file, struct
> ifreq *ifr)
> ret = tun_attach(tun, file);
> } else if (ifr->ifr_flags & IFF_DETACH_QUEUE) {
> tun = rtnl_dereference(tfile->tun);
> - if (!tun || !(tun->flags & TUN_TAP_MQ))
> + if (!tun || !(tun->flags & TUN_TAP_MQ) || tfile->detached)
> ret = -EINVAL;
> else
> __tun_detach(tfile, false);
> --
> 1.7.1
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