[PATCH 2/2] RDMA/erdma: Hold QP references for AE and CM processing

[Cheng Xu <chengyou@linux.alibaba.com>]

AE QP fatal events and iWARP CM paths load QPs from dev->qp_xa
and then use or reference them outside the xarray lock.
erdma_destroy_qp() can drop the destroy-path reference and free QP
resources while such a lookup is in flight.

Add erdma_qp_get_by_qpn() to acquire a kref under the xarray
lock with kref_get_unless_zero(). Remove the QP from the xarray
before dropping the destroy-path reference so no new lookup can acquire
it while destruction waits for existing users.

Fixes: 155055771704 ("RDMA/erdma: Add verbs implementation")
Signed-off-by: Cheng Xu <chengyou@linux.alibaba.com>
---
 drivers/infiniband/hw/erdma/erdma_cm.c    |  6 ++----
 drivers/infiniband/hw/erdma/erdma_eq.c    |  3 ++-
 drivers/infiniband/hw/erdma/erdma_verbs.c |  6 +++++-
 drivers/infiniband/hw/erdma/erdma_verbs.h | 15 +++++++++++++++
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/infiniband/hw/erdma/erdma_cm.c b/drivers/infiniband/hw/erdma/erdma_cm.c
index 5c7d3a8f8038..70c5df566d9d 100644
--- a/drivers/infiniband/hw/erdma/erdma_cm.c
+++ b/drivers/infiniband/hw/erdma/erdma_cm.c
@@ -1021,10 +1021,9 @@ int erdma_connect(struct iw_cm_id *id, struct iw_cm_conn_param *params)
 	if (laddr->sa_family != AF_INET || raddr->sa_family != AF_INET)
 		return -EAFNOSUPPORT;
 
-	qp = find_qp_by_qpn(dev, params->qpn);
+	qp = erdma_qp_get_by_qpn(dev, params->qpn);
 	if (!qp)
 		return -ENOENT;
-	erdma_qp_get(qp);
 
 	ret = sock_create(AF_INET, SOCK_STREAM, IPPROTO_TCP, &s);
 	if (ret < 0)
@@ -1154,10 +1153,9 @@ int erdma_accept(struct iw_cm_id *id, struct iw_cm_conn_param *params)
 		return -ECONNRESET;
 	}
 
-	qp = find_qp_by_qpn(dev, params->qpn);
+	qp = erdma_qp_get_by_qpn(dev, params->qpn);
 	if (!qp)
 		return -ENOENT;
-	erdma_qp_get(qp);
 
 	down_write(&qp->state_lock);
 	if (qp->attrs.iwarp.state > ERDMA_QPS_IWARP_RTR) {
diff --git a/drivers/infiniband/hw/erdma/erdma_eq.c b/drivers/infiniband/hw/erdma/erdma_eq.c
index 96e74fcf417c..d5d1704cb57c 100644
--- a/drivers/infiniband/hw/erdma/erdma_eq.c
+++ b/drivers/infiniband/hw/erdma/erdma_eq.c
@@ -65,7 +65,7 @@ void erdma_aeq_event_handler(struct erdma_dev *dev)
 			erdma_cq_put(cq);
 		} else {
 			qpn = le32_to_cpu(aeqe->event_data0);
-			qp = find_qp_by_qpn(dev, qpn);
+			qp = erdma_qp_get_by_qpn(dev, qpn);
 			if (!qp)
 				continue;
 
@@ -75,6 +75,7 @@ void erdma_aeq_event_handler(struct erdma_dev *dev)
 			if (qp->ibqp.event_handler)
 				qp->ibqp.event_handler(&event,
 						       qp->ibqp.qp_context);
+			erdma_qp_put(qp);
 		}
 	}
 
diff --git a/drivers/infiniband/hw/erdma/erdma_verbs.c b/drivers/infiniband/hw/erdma/erdma_verbs.c
index 2adcd00c4199..65b1af1e6623 100644
--- a/drivers/infiniband/hw/erdma/erdma_verbs.c
+++ b/drivers/infiniband/hw/erdma/erdma_verbs.c
@@ -1369,6 +1369,7 @@ int erdma_destroy_qp(struct ib_qp *ibqp, struct ib_udata *udata)
 		udata, struct erdma_ucontext, ibucontext);
 	struct erdma_cmdq_destroy_qp_req req;
 	union erdma_mod_qp_params params;
+	unsigned long flags;
 	int err;
 
 	down_write(&qp->state_lock);
@@ -1396,6 +1397,10 @@ int erdma_destroy_qp(struct ib_qp *ibqp, struct ib_udata *udata)
 				       "failed to destroy QP %u: %d\n",
 				       QP_ID(qp), err);
 
+	xa_lock_irqsave(&dev->qp_xa, flags);
+	__xa_erase(&dev->qp_xa, QP_ID(qp));
+	xa_unlock_irqrestore(&dev->qp_xa, flags);
+
 	erdma_qp_put(qp);
 	wait_for_completion(&qp->safe_free);
 
@@ -1409,7 +1414,6 @@ int erdma_destroy_qp(struct ib_qp *ibqp, struct ib_udata *udata)
 
 	if (qp->cep)
 		erdma_cep_put(qp->cep);
-	xa_erase(&dev->qp_xa, QP_ID(qp));
 
 	return 0;
 }
diff --git a/drivers/infiniband/hw/erdma/erdma_verbs.h b/drivers/infiniband/hw/erdma/erdma_verbs.h
index 894e080435fb..c73cecf92f61 100644
--- a/drivers/infiniband/hw/erdma/erdma_verbs.h
+++ b/drivers/infiniband/hw/erdma/erdma_verbs.h
@@ -360,6 +360,21 @@ static inline struct erdma_qp *find_qp_by_qpn(struct erdma_dev *dev, int id)
 	return (struct erdma_qp *)xa_load(&dev->qp_xa, id);
 }
 
+static inline struct erdma_qp *erdma_qp_get_by_qpn(struct erdma_dev *dev,
+						   int id)
+{
+	struct erdma_qp *qp;
+	unsigned long flags;
+
+	xa_lock_irqsave(&dev->qp_xa, flags);
+	qp = xa_load(&dev->qp_xa, id);
+	if (qp && !kref_get_unless_zero(&qp->ref))
+		qp = NULL;
+	xa_unlock_irqrestore(&dev->qp_xa, flags);
+
+	return qp;
+}
+
 static inline struct erdma_cq *erdma_cq_get_by_cqn(struct erdma_dev *dev,
 						   int id)
 {
-- 
2.31.1