scsi: qla2xxx: Add IOCB resource tracking

This patch tracks number of IOCB resources used in the I/O fast path. If
the number of used IOCBs reach a high water limit, driver would return the
I/O as busy and let upper layer retry. This prevents over subscription of
IOCB resources where any future error recovery command is unable to cut
through.  Enable IOCB throttling by default.

Link: https://lore.kernel.org/r/20200904045128.23631-12-njavali@marvell.com
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Quinn Tran <qutran@marvell.com>
Signed-off-by: Arun Easi <aeasi@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/drivers/scsi/qla2xxx/qla_inline.h b/drivers/scsi/qla2xxx/qla_inline.h
index 5b04da8a64c7..c7aae438f984 100644
--- a/drivers/scsi/qla2xxx/qla_inline.h
+++ b/drivers/scsi/qla2xxx/qla_inline.h
@@ -378,3 +378,58 @@ qla2xxx_get_fc4_priority(struct scsi_qla_host *vha)
 
 	return (data >> 6) & BIT_0 ? FC4_PRIORITY_FCP : FC4_PRIORITY_NVME;
 }
+
+enum {
+	RESOURCE_NONE,
+	RESOURCE_INI,
+};
+
+static inline int
+qla_get_iocbs(struct qla_qpair *qp, struct iocb_resource *iores)
+{
+	u16 iocbs_used, i;
+	struct qla_hw_data *ha = qp->vha->hw;
+
+	if (!ql2xenforce_iocb_limit) {
+		iores->res_type = RESOURCE_NONE;
+		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 {
+		/* 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++) {
+			if (ha->queue_pair_map[i])
+				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 {
+			iores->res_type = RESOURCE_NONE;
+			return -ENOSPC;
+		}
+	}
+}
+
+static inline void
+qla_put_iocbs(struct qla_qpair *qp, struct iocb_resource *iores)
+{
+	switch (iores->res_type) {
+	case RESOURCE_NONE:
+		break;
+	default:
+		if (qp->fwres.iocbs_used >= iores->iocb_cnt) {
+			qp->fwres.iocbs_used -= iores->iocb_cnt;
+		} else {
+			// should not happen
+			qp->fwres.iocbs_used = 0;
+		}
+		break;
+	}
+	iores->res_type = RESOURCE_NONE;
+}