scsi: qla2xxx: Fix exchange oversubscription

In large environment, it is possible to experience command timeout and
escalation of path recovery. Currently the driver does not track the number
of exchanges/commands sent to FW. If there is a delay for commands at the
head of the queue, then this will create back pressure for commands at the
back of the queue.

Check for exchange availability before command submission.

Fixes: 89c72f4245a8 ("scsi: qla2xxx: Add IOCB resource tracking")
Signed-off-by: Quinn Tran <qutran@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 35 insertions, 17 deletions

diff --git a/drivers/scsi/qla2xxx/qla_inline.h b/drivers/scsi/qla2xxx/qla_inline.h
index 5185dc5daf80..2d5a275d8b00 100644
--- a/drivers/scsi/qla2xxx/qla_inline.h
+++ b/drivers/scsi/qla2xxx/qla_inline.h
@@ -380,13 +380,16 @@ qla2xxx_get_fc4_priority(struct scsi_qla_host *vha)
 
 enum {
 	RESOURCE_NONE,
-	RESOURCE_INI,
+	RESOURCE_IOCB  = BIT_0,
+	RESOURCE_EXCH = BIT_1,  /* exchange */
+	RESOURCE_FORCE = BIT_2,
 };
 
 static inline int
-qla_get_iocbs(struct qla_qpair *qp, struct iocb_resource *iores)
+qla_get_fw_resources(struct qla_qpair *qp, struct iocb_resource *iores)
 {
 	u16 iocbs_used, i;
+	u16 exch_used;
 	struct qla_hw_data *ha = qp->vha->hw;
 
 	if (!ql2xenforce_iocb_limit) {
@@ -394,10 +397,7 @@ qla_get_iocbs(struct qla_qpair *qp, struct iocb_resource *iores)
 		return 0;
 	}
 
-	if ((iores->iocb_cnt + qp->fwres.iocbs_used) < qp->fwres.iocbs_qp_limit) {
-		qp->fwres.iocbs_used += iores->iocb_cnt;
-		return 0;
-	} else {
+	if ((iores->iocb_cnt + qp->fwres.iocbs_used) >= qp->fwres.iocbs_qp_limit) {
 		/* no need to acquire qpair lock. It's just rough calculation */
 		iocbs_used = ha->base_qpair->fwres.iocbs_used;
 		for (i = 0; i < ha->max_qpairs; i++) {
@@ -405,30 +405,48 @@ qla_get_iocbs(struct qla_qpair *qp, struct iocb_resource *iores)
 				iocbs_used += ha->queue_pair_map[i]->fwres.iocbs_used;
 		}
 
-		if ((iores->iocb_cnt + iocbs_used) < qp->fwres.iocbs_limit) {
-			qp->fwres.iocbs_used += iores->iocb_cnt;
-			return 0;
-		} else {
+		if ((iores->iocb_cnt + iocbs_used) >= qp->fwres.iocbs_limit) {
+			iores->res_type = RESOURCE_NONE;
+			return -ENOSPC;
+		}
+	}
+
+	if (iores->res_type & RESOURCE_EXCH) {
+		exch_used = ha->base_qpair->fwres.exch_used;
+		for (i = 0; i < ha->max_qpairs; i++) {
+			if (ha->queue_pair_map[i])
+				exch_used += ha->queue_pair_map[i]->fwres.exch_used;
+		}
+
+		if ((exch_used + iores->exch_cnt) >= qp->fwres.exch_limit) {
 			iores->res_type = RESOURCE_NONE;
 			return -ENOSPC;
 		}
 	}
+	qp->fwres.iocbs_used += iores->iocb_cnt;
+	qp->fwres.exch_used += iores->exch_cnt;
+	return 0;
 }
 
 static inline void
-qla_put_iocbs(struct qla_qpair *qp, struct iocb_resource *iores)
+qla_put_fw_resources(struct qla_qpair *qp, struct iocb_resource *iores)
 {
-	switch (iores->res_type) {
-	case RESOURCE_NONE:
-		break;
-	default:
+	if (iores->res_type & RESOURCE_IOCB) {
 		if (qp->fwres.iocbs_used >= iores->iocb_cnt) {
 			qp->fwres.iocbs_used -= iores->iocb_cnt;
 		} else {
-			// should not happen
+			/* should not happen */
 			qp->fwres.iocbs_used = 0;
 		}
-		break;
+	}
+
+	if (iores->res_type & RESOURCE_EXCH) {
+		if (qp->fwres.exch_used >= iores->exch_cnt) {
+			qp->fwres.exch_used -= iores->exch_cnt;
+		} else {
+			/* should not happen */
+			qp->fwres.exch_used = 0;
+		}
 	}
 	iores->res_type = RESOURCE_NONE;
 }