IB/hfi1: Fix incorrect mixing of ERR_PTR and NULL return values

The __get_txreq() function can return a pointer, ERR_PTR(-EBUSY), or NULL.
All of the relevant call sites look for IS_ERR, so the NULL return would
lead to a NULL pointer exception.

Do not use the ERR_PTR mechanism for this function.

Update all call sites to handle the return value correctly.

Clean up error paths to reflect return value.

Fixes: 45842abb ("staging/rdma/hfi1: move txreq header code")
Cc: <stable@vger.kernel.org> # 4.9.x+
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Kamenee Arumugam <kamenee.arumugam@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/hfi1/rc.c

@@ -271,7 +271,7 @@ int hfi1_make_rc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 
 	lockdep_assert_held(&qp->s_lock);
 	ps->s_txreq = get_txreq(ps->dev, qp);
-	if (IS_ERR(ps->s_txreq))
+	if (!ps->s_txreq)
 		goto bail_no_tx;
 
 	if (priv->hdr_type == HFI1_PKT_TYPE_9B) {

drivers/infiniband/hw/hfi1/uc.c

 /*
- * Copyright(c) 2015, 2016 Intel Corporation.
+ * Copyright(c) 2015 - 2018 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
@@ -72,7 +72,7 @@ int hfi1_make_uc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 	int middle = 0;
 
 	ps->s_txreq = get_txreq(ps->dev, qp);
-	if (IS_ERR(ps->s_txreq))
+	if (!ps->s_txreq)
 		goto bail_no_tx;
 
 	if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_SEND_OK)) {

drivers/infiniband/hw/hfi1/ud.c

 /*
- * Copyright(c) 2015, 2016 Intel Corporation.
+ * Copyright(c) 2015 - 2018 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
@@ -503,7 +503,7 @@ int hfi1_make_ud_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 	u32 lid;
 
 	ps->s_txreq = get_txreq(ps->dev, qp);
-	if (IS_ERR(ps->s_txreq))
+	if (!ps->s_txreq)
 		goto bail_no_tx;
 
 	if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_NEXT_SEND_OK)) {

drivers/infiniband/hw/hfi1/verbs_txreq.c

 /*
- * Copyright(c) 2016 - 2017 Intel Corporation.
+ * Copyright(c) 2016 - 2018 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
@@ -94,7 +94,7 @@ struct verbs_txreq *__get_txreq(struct hfi1_ibdev *dev,
 				struct rvt_qp *qp)
 	__must_hold(&qp->s_lock)
 {
-	struct verbs_txreq *tx = ERR_PTR(-EBUSY);
+	struct verbs_txreq *tx = NULL;
 
 	write_seqlock(&dev->txwait_lock);
 	if (ib_rvt_state_ops[qp->state] & RVT_PROCESS_RECV_OK) {

drivers/infiniband/hw/hfi1/verbs_txreq.h

 /*
- * Copyright(c) 2016 Intel Corporation.
+ * Copyright(c) 2016 - 2018 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
@@ -83,7 +83,7 @@ static inline struct verbs_txreq *get_txreq(struct hfi1_ibdev *dev,
 	if (unlikely(!tx)) {
 		/* call slow path to get the lock */
 		tx = __get_txreq(dev, qp);
-		if (IS_ERR(tx))
+		if (!tx)
 			return tx;
 	}
 	tx->qp = qp;