On Tue, Jan 15, 2013 at 06:28:46PM +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,
> vhost/qemu needs to to its own cleanup which is complex. We can do this
> simply
> by allowing a user can still write to an disabled queue to handle this. And
> user can still do read but just nothing returned.
> - 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)
>
> Signed-off-by: Jason Wang <[email protected]>
> ---
> drivers/net/tun.c | 18 +++++++++++-------
> 1 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index af372d0..eb68937 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -307,7 +307,7 @@ static void tun_flow_update(struct tun_struct *tun, u32
> rxhash,
>
> rcu_read_lock();
>
> - if (tun->numqueues == 1)
> + if (tun->numqueues == 1 || queue_index >= tun->numqueues)
> goto unlock;
>
> e = tun_flow_find(head, rxhash);
Hmm I don't understand - does something ensure that queue_index is >
numqueues if the queue is disabled?
Can we check tun->disabled and skip tun_flow_update completely?
We might need to switch to rcu_assign for tun->disabled for this
but otherwise it looks easy.
> @@ -406,21 +406,21 @@ 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();
> @@ -465,6 +465,10 @@ 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();
> @@ -491,7 +495,7 @@ static int tun_attach(struct tun_struct *tun, struct file
> *file)
> int err;
>
> err = -EINVAL;
> - if (rtnl_dereference(tfile->tun))
> + if (rtnl_dereference(tfile->tun) && !tfile->detached)
> goto out;
>
> err = -EBUSY;
> @@ -1795,7 +1799,7 @@ 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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