staging/rdma/hfi1: add common routine for queuing acks

This patch is a prelimary patch required to
coalesce acks.

The routine to "schedule" a QP for sending a NAK is
now centralized in rc_defer_ack().  The flag is changed
for clarity since the all acks will potentially use
the deferral  mechanism.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rdma/hfi1/driver.c

@@ -714,8 +714,8 @@ static inline void process_rcv_qp_work(struct hfi1_packet *packet)
 	 */
 	list_for_each_entry_safe(qp, nqp, &rcd->qp_wait_list, rspwait) {
 		list_del_init(&qp->rspwait);
-		if (qp->r_flags & HFI1_R_RSP_NAK) {
-			qp->r_flags &= ~HFI1_R_RSP_NAK;
+		if (qp->r_flags & HFI1_R_RSP_DEFERED_ACK) {
+			qp->r_flags &= ~HFI1_R_RSP_DEFERED_ACK;
 			hfi1_send_rc_ack(rcd, qp, 0);
 		}
 		if (qp->r_flags & HFI1_R_RSP_SEND) {

drivers/staging/rdma/hfi1/rc.c

@@ -1608,6 +1608,16 @@ static void rc_rcv_resp(struct hfi1_ibport *ibp,
 	return;
 }
 
+static inline void rc_defered_ack(struct hfi1_ctxtdata *rcd,
+				  struct hfi1_qp *qp)
+{
+	if (list_empty(&qp->rspwait)) {
+		qp->r_flags |= HFI1_R_RSP_DEFERED_ACK;
+		atomic_inc(&qp->refcount);
+		list_add_tail(&qp->rspwait, &rcd->qp_wait_list);
+	}
+}
+
 /**
  * rc_rcv_error - process an incoming duplicate or error RC packet
  * @ohdr: the other headers for this packet
@@ -1650,11 +1660,7 @@ static noinline int rc_rcv_error(struct hfi1_other_headers *ohdr, void *data,
 			 * in the receive queue have been processed.
 			 * Otherwise, we end up propagating congestion.
 			 */
-			if (list_empty(&qp->rspwait)) {
-				qp->r_flags |= HFI1_R_RSP_NAK;
-				atomic_inc(&qp->refcount);
-				list_add_tail(&qp->rspwait, &rcd->qp_wait_list);
-			}
+			rc_defered_ack(rcd, qp);
 		}
 		goto done;
 	}
@@ -2337,11 +2343,7 @@ void hfi1_rc_rcv(struct hfi1_packet *packet)
 	qp->r_nak_state = IB_RNR_NAK | qp->r_min_rnr_timer;
 	qp->r_ack_psn = qp->r_psn;
 	/* Queue RNR NAK for later */
-	if (list_empty(&qp->rspwait)) {
-		qp->r_flags |= HFI1_R_RSP_NAK;
-		atomic_inc(&qp->refcount);
-		list_add_tail(&qp->rspwait, &rcd->qp_wait_list);
-	}
+	rc_defered_ack(rcd, qp);
 	return;
 
 nack_op_err:
@@ -2349,11 +2351,7 @@ void hfi1_rc_rcv(struct hfi1_packet *packet)
 	qp->r_nak_state = IB_NAK_REMOTE_OPERATIONAL_ERROR;
 	qp->r_ack_psn = qp->r_psn;
 	/* Queue NAK for later */
-	if (list_empty(&qp->rspwait)) {
-		qp->r_flags |= HFI1_R_RSP_NAK;
-		atomic_inc(&qp->refcount);
-		list_add_tail(&qp->rspwait, &rcd->qp_wait_list);
-	}
+	rc_defered_ack(rcd, qp);
 	return;
 
 nack_inv_unlck:
@@ -2363,11 +2361,7 @@ void hfi1_rc_rcv(struct hfi1_packet *packet)
 	qp->r_nak_state = IB_NAK_INVALID_REQUEST;
 	qp->r_ack_psn = qp->r_psn;
 	/* Queue NAK for later */
-	if (list_empty(&qp->rspwait)) {
-		qp->r_flags |= HFI1_R_RSP_NAK;
-		atomic_inc(&qp->refcount);
-		list_add_tail(&qp->rspwait, &rcd->qp_wait_list);
-	}
+	rc_defered_ack(rcd, qp);
 	return;
 
 nack_acc_unlck:
@@ -2421,13 +2415,7 @@ void hfi1_rc_hdrerr(
 			 * Otherwise, we end up
 			 * propagating congestion.
 			 */
-			if (list_empty(&qp->rspwait)) {
-				qp->r_flags |= HFI1_R_RSP_NAK;
-				atomic_inc(&qp->refcount);
-				list_add_tail(
-					&qp->rspwait,
-					&rcd->qp_wait_list);
-				}
+			rc_defered_ack(rcd, qp);
 		} /* Out of sequence NAK */
 	} /* QP Request NAKs */
 }

drivers/staging/rdma/hfi1/verbs.h

@@ -555,7 +555,9 @@ struct hfi1_qp {
  */
 #define HFI1_R_REUSE_SGE       0x01
 #define HFI1_R_RDMAR_SEQ       0x02
-#define HFI1_R_RSP_NAK   0x04
+/* defer ack until end of interrupt session */
+#define HFI1_R_RSP_DEFERED_ACK 0x04
+/* relay ack to send engine */
 #define HFI1_R_RSP_SEND        0x08
 #define HFI1_R_COMM_EST        0x10