[PATCH v1 01/11] IB/rxe: Move refcounting earlier in rxe_send()

Andrew Boyer
2017-08-25T19:05:46Z

The network stack will call nskb's destructor, rxe_skb_tx_dtor(), if the
packet gets dropped by ip_local_out()/ip6_local_out(). Thus we need to add
the QP ref before output to avoid extra dereferences during network
congestion. This could lead to unwanted destruction of the QP.

Fix up the skb_out accounting, too.

Fixes: fda85ce91240 ("IB/rxe: Fix kernel panic from skb destructor")
Signed-off-by: Andrew Boyer <andrew.boyer-8PEkshWhKlo@public.gmane.org>
Acked-by: Moni Shoua <monis-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
drivers/infiniband/sw/rxe/rxe_net.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
index 08f3f90..0810f38 100644
--- a/drivers/infiniband/sw/rxe/rxe_net.c
+++ b/drivers/infiniband/sw/rxe/rxe_net.c
@@ -460,12 +460,17 @@ int rxe_send(struct rxe_dev *rxe, struct rxe_pkt_info *pkt, struct sk_buff *skb)
nskb->destructor = rxe_skb_tx_dtor;
nskb->sk = pkt->qp->sk->sk;

+ rxe_add_ref(pkt->qp);
+ atomic_inc(&pkt->qp->skb_out);
+
if (av->network_type == RDMA_NETWORK_IPV4) {
err = ip_local_out(dev_net(skb_dst(skb)->dev), nskb->sk, nskb);
} else if (av->network_type == RDMA_NETWORK_IPV6) {
err = ip6_local_out(dev_net(skb_dst(skb)->dev), nskb->sk, nskb);
} else {
pr_err("Unknown layer 3 protocol: %d\n", av->network_type);
+ atomic_dec(&pkt->qp->skb_out);
+ rxe_drop_ref(pkt->qp);
kfree_skb(nskb);
return -EINVAL;
}
@@ -475,10 +480,7 @@ int rxe_send(struct rxe_dev *rxe, struct rxe_pkt_info *pkt, struct sk_buff *skb)
return -EAGAIN;
}

- rxe_add_ref(pkt->qp);
- atomic_inc(&pkt->qp->skb_out);
kfree_skb(skb);
-
return 0;
}