Messages in this thread Patch in this message | | | From | Jason Wang <> | Subject | [PATCH net V3 2/2] tuntap: synchronize through tfiles array instead of tun->numqueues | Date | Wed, 8 May 2019 23:20:18 -0400 |
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When a queue(tfile) is detached through __tun_detach(), we move the last enabled tfile to the position where detached one sit but don't NULL out last position. We expect to synchronize the datapath through tun->numqueues. Unfortunately, this won't work since we're lacking sufficient mechanism to order or synchronize the access to tun->numqueues.
To fix this, NULL out the last position during detaching and check RCU protected tfile against NULL instead of checking tun->numqueues in datapath.
Cc: YueHaibing <yuehaibing@huawei.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: weiyongjun (A) <weiyongjun1@huawei.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Fixes: c8d68e6be1c3b ("tuntap: multiqueue support") Signed-off-by: Jason Wang <jasowang@redhat.com> --- Changes from V2: - resample during detach in tun_xdp_xmit() Changes from V1: - keep the check in tun_xdp_xmit() --- drivers/net/tun.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index dc62fc3..f4c933a 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -705,6 +705,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean) tun->tfiles[tun->numqueues - 1]); ntfile = rtnl_dereference(tun->tfiles[index]); ntfile->queue_index = index; + rcu_assign_pointer(tun->tfiles[tun->numqueues - 1], + NULL); --tun->numqueues; if (clean) { @@ -1087,7 +1089,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) tfile = rcu_dereference(tun->tfiles[txq]); /* Drop packet if interface is not attached */ - if (txq >= tun->numqueues) + if (!tfile) goto drop; if (!rcu_dereference(tun->steering_prog)) @@ -1310,6 +1312,7 @@ static int tun_xdp_xmit(struct net_device *dev, int n, rcu_read_lock(); +resample: numqueues = READ_ONCE(tun->numqueues); if (!numqueues) { rcu_read_unlock(); @@ -1318,6 +1321,8 @@ static int tun_xdp_xmit(struct net_device *dev, int n, tfile = rcu_dereference(tun->tfiles[smp_processor_id() % numqueues]); + if (unlikely(!tfile)) + goto resample; spin_lock(&tfile->tx_ring.producer_lock); for (i = 0; i < n; i++) { -- 1.8.3.1
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