[PATCH for-next v2 12/12] RDMA/rxe: Let destroy qp succeed with stuck packet

[Bob Pearson <rpearsonhpe@gmail.com>]

In some situations a sent packet may get queued in the NIC longer
than the timeout of a ULP. Currently if this happens the ULP may
try to reset the link by destroying the qp and setting up an
alternate connection but will fail because the rxe driver is
waiting for the packet to finish getting sent and be returned to
the skb destructor function where the qp reference holding things
up will be dropped. This patch modifies the way that the qp is
passed to the destructor to pass the qp index and not a qp pointer.
Then the destructor will attempt to lookup the qp from its index
and if it fails exit early. This requires taking a reference on
the struct sock rather than the qp allowing the qp to be destroyed
while the sk is still around waiting for the packet to finish.

Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
---
 drivers/infiniband/sw/rxe/rxe_net.c | 42 +++++++++++++++++++++--------
 drivers/infiniband/sw/rxe/rxe_qp.c  |  2 +-
 2 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
index b58eab75df97..dc22f3922a59 100644
--- a/drivers/infiniband/sw/rxe/rxe_net.c
+++ b/drivers/infiniband/sw/rxe/rxe_net.c
@@ -345,25 +345,44 @@ int rxe_prepare(struct rxe_av *av, struct rxe_pkt_info *pkt,
 
 static void rxe_skb_tx_dtor(struct sk_buff *skb)
 {
-	struct sock *sk = skb->sk;
-	struct rxe_qp *qp = sk->sk_user_data;
-	int skb_out = atomic_dec_return(&qp->skb_out);
+	struct net_device *ndev = skb->dev;
+	struct rxe_dev *rxe;
+	unsigned int qp_index;
+	struct rxe_qp *qp;
+	int skb_out;
+
+	rxe = rxe_get_dev_from_net(ndev);
+	if (!rxe && is_vlan_dev(ndev))
+		rxe = rxe_get_dev_from_net(vlan_dev_real_dev(ndev));
+	if (WARN_ON(!rxe))
+		return;
 
-	if (unlikely(qp->need_req_skb &&
-		     skb_out < RXE_INFLIGHT_SKBS_PER_QP_LOW))
+	qp_index = (int)(uintptr_t)skb->sk->sk_user_data;
+	if (!qp_index)
+		return;
+
+	qp = rxe_pool_get_index(&rxe->qp_pool, qp_index);
+	if (!qp)
+		goto put_dev;
+
+	skb_out = atomic_dec_return(&qp->skb_out);
+	if (qp->need_req_skb && skb_out < RXE_INFLIGHT_SKBS_PER_QP_LOW)
 		rxe_sched_task(&qp->send_task);
 
 	rxe_put(qp);
+put_dev:
+	ib_device_put(&rxe->ib_dev);
+	sock_put(skb->sk);
 }
 
 static int rxe_send(struct sk_buff *skb, struct rxe_pkt_info *pkt)
 {
 	int err;
+	struct sock *sk = pkt->qp->sk->sk;
 
+	sock_hold(sk);
+	skb->sk = sk;
 	skb->destructor = rxe_skb_tx_dtor;
-	skb->sk = pkt->qp->sk->sk;
-
-	rxe_get(pkt->qp);
 	atomic_inc(&pkt->qp->skb_out);
 
 	if (skb->protocol == htons(ETH_P_IP))
@@ -379,12 +398,13 @@ static int rxe_send(struct sk_buff *skb, struct rxe_pkt_info *pkt)
  */
 static int rxe_loopback(struct sk_buff *skb, struct rxe_pkt_info *pkt)
 {
+	struct sock *sk = pkt->qp->sk->sk;
+
 	memcpy(SKB_TO_PKT(skb), pkt, sizeof(*pkt));
 
+	sock_hold(sk);
+	skb->sk = sk;
 	skb->destructor = rxe_skb_tx_dtor;
-	skb->sk = pkt->qp->sk->sk;
-
-	rxe_get(pkt->qp);
 	atomic_inc(&pkt->qp->skb_out);
 
 	if (skb->protocol == htons(ETH_P_IP))
diff --git a/drivers/infiniband/sw/rxe/rxe_qp.c b/drivers/infiniband/sw/rxe/rxe_qp.c
index c7d99063594b..d2f7b5195c19 100644
--- a/drivers/infiniband/sw/rxe/rxe_qp.c
+++ b/drivers/infiniband/sw/rxe/rxe_qp.c
@@ -244,7 +244,7 @@ static int rxe_qp_init_req(struct rxe_dev *rxe, struct rxe_qp *qp,
 	err = sock_create_kern(&init_net, AF_INET, SOCK_DGRAM, 0, &qp->sk);
 	if (err < 0)
 		return err;
-	qp->sk->sk->sk_user_data = qp;
+	qp->sk->sk->sk_user_data = (void *)(uintptr_t)qp->elem.index;
 
 	/* pick a source UDP port number for this QP based on
 	 * the source QPN. this spreads traffic for different QPs
-- 
2.43.0