RDMA/cxgb4: 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/1622194663-2383-12-git-send-email-liweihang@huawei.com
Cc: Potnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/cxgb4/cq.c

@@ -976,8 +976,8 @@ int c4iw_destroy_cq(struct ib_cq *ib_cq, struct ib_udata *udata)
 	chp = to_c4iw_cq(ib_cq);
 
 	xa_erase_irq(&chp->rhp->cqs, chp->cq.cqid);
-	atomic_dec(&chp->refcnt);
-	wait_event(chp->wait, !atomic_read(&chp->refcnt));
+	refcount_dec(&chp->refcnt);
+	wait_event(chp->wait, !refcount_read(&chp->refcnt));
 
 	ucontext = rdma_udata_to_drv_context(udata, struct c4iw_ucontext,
 					     ibucontext);
@@ -1080,7 +1080,7 @@ int c4iw_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 	chp->ibcq.cqe = entries - 2;
 	spin_lock_init(&chp->lock);
 	spin_lock_init(&chp->comp_handler_lock);
-	atomic_set(&chp->refcnt, 1);
+	refcount_set(&chp->refcnt, 1);
 	init_waitqueue_head(&chp->wait);
 	ret = xa_insert_irq(&rhp->cqs, chp->cq.cqid, chp, GFP_KERNEL);
 	if (ret)

drivers/infiniband/hw/cxgb4/ev.c

@@ -151,7 +151,7 @@ void c4iw_ev_dispatch(struct c4iw_dev *dev, struct t4_cqe *err_cqe)
 	}
 
 	c4iw_qp_add_ref(&qhp->ibqp);
-	atomic_inc(&chp->refcnt);
+	refcount_inc(&chp->refcnt);
 	xa_unlock_irq(&dev->qps);
 
 	/* Bad incoming write */
@@ -213,7 +213,7 @@ void c4iw_ev_dispatch(struct c4iw_dev *dev, struct t4_cqe *err_cqe)
 		break;
 	}
 done:
-	if (atomic_dec_and_test(&chp->refcnt))
+	if (refcount_dec_and_test(&chp->refcnt))
 		wake_up(&chp->wait);
 	c4iw_qp_rem_ref(&qhp->ibqp);
 out:
@@ -228,13 +228,13 @@ int c4iw_ev_handler(struct c4iw_dev *dev, u32 qid)
 	xa_lock_irqsave(&dev->cqs, flag);
 	chp = xa_load(&dev->cqs, qid);
 	if (chp) {
-		atomic_inc(&chp->refcnt);
+		refcount_inc(&chp->refcnt);
 		xa_unlock_irqrestore(&dev->cqs, flag);
 		t4_clear_cq_armed(&chp->cq);
 		spin_lock_irqsave(&chp->comp_handler_lock, flag);
 		(*chp->ibcq.comp_handler)(&chp->ibcq, chp->ibcq.cq_context);
 		spin_unlock_irqrestore(&chp->comp_handler_lock, flag);
-		if (atomic_dec_and_test(&chp->refcnt))
+		if (refcount_dec_and_test(&chp->refcnt))
 			wake_up(&chp->wait);
 	} else {
 		pr_debug("unknown cqid 0x%x\n", qid);

drivers/infiniband/hw/cxgb4/iw_cxgb4.h

@@ -427,7 +427,7 @@ struct c4iw_cq {
 	struct t4_cq cq;
 	spinlock_t lock;
 	spinlock_t comp_handler_lock;
-	atomic_t refcnt;
+	refcount_t refcnt;
 	wait_queue_head_t wait;
 	struct c4iw_wr_wait *wr_waitp;
 };