RDMA/cma: Use rdma_read_gid_attr_ndev_rcu to access netdev

To access the netdevice of the GID attribute, use an existing API
rdma_read_gid_attr_ndev_rcu().

This further reduces dependency on open access to netdevice of GID
attribute.
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/addr.c

@@ -45,6 +45,7 @@
 #include <net/addrconf.h>
 #include <net/ip6_route.h>
 #include <rdma/ib_addr.h>
+#include <rdma/ib_cache.h>
 #include <rdma/ib_sa.h>
 #include <rdma/ib.h>
 #include <rdma/rdma_netlink.h>

drivers/infiniband/core/cache.c

@@ -1249,6 +1249,7 @@ struct net_device *rdma_read_gid_attr_ndev_rcu(const struct ib_gid_attr *attr)
 	read_unlock_irqrestore(&table->rwlock, flags);
 	return ndev;
 }
+EXPORT_SYMBOL(rdma_read_gid_attr_ndev_rcu);
 
 static int get_lower_dev_vlan(struct net_device *lower_dev, void *data)
 {

drivers/infiniband/core/cma.c

@@ -1486,6 +1486,7 @@ static struct net_device *
 roce_get_net_dev_by_cm_event(const struct ib_cm_event *ib_event)
 {
 	const struct ib_gid_attr *sgid_attr = NULL;
+	struct net_device *ndev;
 
 	if (ib_event->event == IB_CM_REQ_RECEIVED)
 		sgid_attr = ib_event->param.req_rcvd.ppath_sgid_attr;
@@ -1494,8 +1495,15 @@ roce_get_net_dev_by_cm_event(const struct ib_cm_event *ib_event)
 
 	if (!sgid_attr)
 		return NULL;
-	dev_hold(sgid_attr->ndev);
-	return sgid_attr->ndev;
+
+	rcu_read_lock();
+	ndev = rdma_read_gid_attr_ndev_rcu(sgid_attr);
+	if (IS_ERR(ndev))
+		ndev = NULL;
+	else
+		dev_hold(ndev);
+	rcu_read_unlock();
+	return ndev;
 }
 
 static struct net_device *cma_get_net_dev(const struct ib_cm_event *ib_event,

include/rdma/ib_cache.h

@@ -56,6 +56,7 @@ const struct ib_gid_attr *rdma_find_gid_by_filter(
 
 int rdma_read_gid_l2_fields(const struct ib_gid_attr *attr,
 			    u16 *vlan_id, u8 *smac);
+struct net_device *rdma_read_gid_attr_ndev_rcu(const struct ib_gid_attr *attr);
 
 /**
  * ib_get_cached_pkey - Returns a cached PKey table entry