RDMA/ipoib: Use refcount_t instead of atomic_t for reference counting

The refcount_t API will WARN on underflow and overflow of a reference
counter, and avoid use-after-free risks.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Weihang Li <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/ulp/ipoib/ipoib.h

···
 	struct list_head    list;
 	struct ipoib_neigh __rcu *hnext;
 	struct rcu_head     rcu;
-	atomic_t	    refcnt;
+	refcount_t	    refcnt;
 	unsigned long       alive;
 };
 
···
 void ipoib_neigh_dtor(struct ipoib_neigh *neigh);
 static inline void ipoib_neigh_put(struct ipoib_neigh *neigh)
 {
-	if (atomic_dec_and_test(&neigh->refcnt))
+	if (refcount_dec_and_test(&neigh->refcnt))
 		ipoib_neigh_dtor(neigh);
 }
 struct ipoib_neigh *ipoib_neigh_get(struct net_device *dev, u8 *daddr);

drivers/infiniband/ulp/ipoib/ipoib_main.c

···
 	     neigh = rcu_dereference_bh(neigh->hnext)) {
 		if (memcmp(daddr, neigh->daddr, INFINIBAND_ALEN) == 0) {
 			/* found, take one ref on behalf of the caller */
-			if (!atomic_inc_not_zero(&neigh->refcnt)) {
+			if (!refcount_inc_not_zero(&neigh->refcnt)) {
 				/* deleted */
 				neigh = NULL;
 				goto out_unlock;
···
 	INIT_LIST_HEAD(&neigh->list);
 	ipoib_cm_set(neigh, NULL);
 	/* one ref on behalf of the caller */
-	atomic_set(&neigh->refcnt, 1);
+	refcount_set(&neigh->refcnt, 1);
 
 	return neigh;
 }
···
 					       lockdep_is_held(&priv->lock))) {
 		if (memcmp(daddr, neigh->daddr, INFINIBAND_ALEN) == 0) {
 			/* found, take one ref on behalf of the caller */
-			if (!atomic_inc_not_zero(&neigh->refcnt)) {
+			if (!refcount_inc_not_zero(&neigh->refcnt)) {
 				/* deleted */
 				neigh = NULL;
 				break;
···
 		goto out_unlock;
 
 	/* one ref on behalf of the hash table */
-	atomic_inc(&neigh->refcnt);
+	refcount_inc(&neigh->refcnt);
 	neigh->alive = jiffies;
 	/* put in hash */
 	rcu_assign_pointer(neigh->hnext,