RDMA/hns: Use refcount_t instead of atomic_t for SRQ 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/1622194663-2383-10-git-send-email-liweihang@huawei.com
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/hns/hns_roce_device.h

@@ -471,7 +471,7 @@ struct hns_roce_srq {
 	u32			xrcdn;
 	void __iomem		*db_reg;
 
-	atomic_t		refcount;
+	refcount_t		refcount;
 	struct completion	free;
 
 	struct hns_roce_mtr	buf_mtr;

drivers/infiniband/hw/hns/hns_roce_srq.c

@@ -17,7 +17,7 @@ void hns_roce_srq_event(struct hns_roce_dev *hr_dev, u32 srqn, int event_type)
 	xa_lock(&srq_table->xa);
 	srq = xa_load(&srq_table->xa, srqn & (hr_dev->caps.num_srqs - 1));
 	if (srq)
-		atomic_inc(&srq->refcount);
+		refcount_inc(&srq->refcount);
 	xa_unlock(&srq_table->xa);
 
 	if (!srq) {
@@ -27,7 +27,7 @@ void hns_roce_srq_event(struct hns_roce_dev *hr_dev, u32 srqn, int event_type)
 
 	srq->event(srq, event_type);
 
-	if (atomic_dec_and_test(&srq->refcount))
+	if (refcount_dec_and_test(&srq->refcount))
 		complete(&srq->free);
 }
 
@@ -149,7 +149,7 @@ static void free_srqc(struct hns_roce_dev *hr_dev, struct hns_roce_srq *srq)
 
 	xa_erase(&srq_table->xa, srq->srqn);
 
-	if (atomic_dec_and_test(&srq->refcount))
+	if (refcount_dec_and_test(&srq->refcount))
 		complete(&srq->free);
 	wait_for_completion(&srq->free);
 
@@ -417,7 +417,7 @@ int hns_roce_create_srq(struct ib_srq *ib_srq,
 
 	srq->db_reg = hr_dev->reg_base + SRQ_DB_REG;
 	srq->event = hns_roce_ib_srq_event;
-	atomic_set(&srq->refcount, 1);
+	refcount_set(&srq->refcount, 1);
 	init_completion(&srq->free);
 
 	return 0;