RDMA/cxgb4: Fix accounting for unsignaled SQ WRs to deal with wrap

When determining how many WRs are completed with a signaled CQE,
correctly deal with queue wraps.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Vipul Pandya <vipul@chelsio.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/cxgb4/cq.c

@@ -611,9 +611,12 @@ static int poll_cq(struct t4_wq *wq, struct t4_cq *cq, struct t4_cqe *cqe,
 		* to the first unsignaled one, and idx points to the
 		* signaled one.  So adjust in_use based on this delta.
 		* if this is not completing any unsigned wrs, then the
-		* delta will be 0.
+		* delta will be 0. Handle wrapping also!
 		*/
-		wq->sq.in_use -= idx - wq->sq.cidx;
+		if (idx < wq->sq.cidx)
+			wq->sq.in_use -= wq->sq.size + idx - wq->sq.cidx;
+		else
+			wq->sq.in_use -= idx - wq->sq.cidx;
 		BUG_ON(wq->sq.in_use < 0 && wq->sq.in_use < wq->sq.size);
 
 		wq->sq.cidx = (uint16_t)idx;