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>

drivers/scsi/qla2xxx/qla_def.h

@@ -624,6 +624,12 @@ enum {
 	TYPE_TGT_TMCMD,		/* task management */
 };
 
+struct iocb_resource {
+	u8 res_type;
+	u8 pad;
+	u16 iocb_cnt;
+};
+
 typedef struct srb {
 	/*
 	 * Do not move cmd_type field, it needs to
@@ -631,6 +637,7 @@ typedef struct srb {
 	 */
 	uint8_t cmd_type;
 	uint8_t pad[3];
+	struct iocb_resource iores;
 	struct kref cmd_kref;	/* need to migrate ref_count over to this */
 	void *priv;
 	wait_queue_head_t nvme_ls_waitq;
@@ -3577,6 +3584,15 @@ struct req_que {
 	uint8_t req_pkt[REQUEST_ENTRY_SIZE];
 };
 
+struct qla_fw_resources {
+	u16 iocbs_total;
+	u16 iocbs_limit;
+	u16 iocbs_qp_limit;
+	u16 iocbs_used;
+};
+
+#define QLA_IOCB_PCT_LIMIT 95
+
 /*Queue pair data structure */
 struct qla_qpair {
 	spinlock_t qp_lock;
@@ -3629,6 +3645,7 @@ struct qla_qpair {
 	uint64_t retry_term_jiff;
 	struct qla_tgt_counters tgt_counters;
 	uint16_t cpuid;
+	struct qla_fw_resources fwres ____cacheline_aligned;
 };
 
 /* Place holder for FW buffer parameters */

drivers/scsi/qla2xxx/qla_dfs.c

@@ -261,6 +261,8 @@ qla_dfs_fw_resource_cnt_show(struct seq_file *s, void *unused)
 	struct scsi_qla_host *vha = s->private;
 	uint16_t mb[MAX_IOCB_MB_REG];
 	int rc;
+	struct qla_hw_data *ha = vha->hw;
+	u16 iocbs_used, i;
 
 	rc = qla24xx_res_count_wait(vha, mb, SIZEOF_IOCB_MB_REG);
 	if (rc != QLA_SUCCESS) {
@@ -285,6 +287,18 @@ qla_dfs_fw_resource_cnt_show(struct seq_file *s, void *unused)
 		    mb[23]);
 	}
 
+	if (ql2xenforce_iocb_limit) {
+		/* lock is not require. It's an estimate. */
+		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;
+		}
+
+		seq_printf(s, "Driver: estimate iocb used [%d] high water limit [%d]\n",
+			   iocbs_used, ha->base_qpair->fwres.iocbs_limit);
+	}
+
 	return 0;
 }
 

drivers/scsi/qla2xxx/qla_gbl.h

@@ -129,6 +129,8 @@ int qla2x00_reserve_mgmt_server_loop_id(scsi_qla_host_t *);
 void qla_rscn_replay(fc_port_t *fcport);
 void qla24xx_free_purex_item(struct purex_item *item);
 extern bool qla24xx_risc_firmware_invalid(uint32_t *);
+void qla_init_iocb_limit(scsi_qla_host_t *);
+
 
 /*
  * Global Data in qla_os.c source file.
@@ -175,6 +177,7 @@ extern int qla2xuseresexchforels;
 extern int ql2xexlogins;
 extern int ql2xdifbundlinginternalbuffers;
 extern int ql2xfulldump_on_mpifail;
+extern int ql2xenforce_iocb_limit;
 
 extern int qla2x00_loop_reset(scsi_qla_host_t *);
 extern void qla2x00_abort_all_cmds(scsi_qla_host_t *, int);

drivers/scsi/qla2xxx/qla_init.c

@@ -3632,6 +3632,31 @@ out:
 	return ha->flags.lr_detected;
 }
 
+void qla_init_iocb_limit(scsi_qla_host_t *vha)
+{
+	u16 i, num_qps;
+	u32 limit;
+	struct qla_hw_data *ha = vha->hw;
+
+	num_qps = ha->num_qpairs + 1;
+	limit = (ha->orig_fw_iocb_count * QLA_IOCB_PCT_LIMIT) / 100;
+
+	ha->base_qpair->fwres.iocbs_total = ha->orig_fw_iocb_count;
+	ha->base_qpair->fwres.iocbs_limit = limit;
+	ha->base_qpair->fwres.iocbs_qp_limit = limit / num_qps;
+	ha->base_qpair->fwres.iocbs_used = 0;
+	for (i = 0; i < ha->max_qpairs; i++) {
+		if (ha->queue_pair_map[i])  {
+			ha->queue_pair_map[i]->fwres.iocbs_total =
+				ha->orig_fw_iocb_count;
+			ha->queue_pair_map[i]->fwres.iocbs_limit = limit;
+			ha->queue_pair_map[i]->fwres.iocbs_qp_limit =
+				limit / num_qps;
+			ha->queue_pair_map[i]->fwres.iocbs_used = 0;
+		}
+	}
+}
+
 /**
  * qla2x00_setup_chip() - Load and start RISC firmware.
  * @vha: HA context
@@ -3731,6 +3756,7 @@ enable_82xx_npiv:
 						    MIN_MULTI_ID_FABRIC - 1;
 				}
 				qla2x00_get_resource_cnts(vha);
+				qla_init_iocb_limit(vha);
 
 				/*
 				 * Allocate the array of outstanding commands

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;
+}

drivers/scsi/qla2xxx/qla_iocb.c

@@ -1637,6 +1637,12 @@ qla24xx_start_scsi(srb_t *sp)
 
 	tot_dsds = nseg;
 	req_cnt = qla24xx_calc_iocbs(vha, tot_dsds);
+
+	sp->iores.res_type = RESOURCE_INI;
+	sp->iores.iocb_cnt = req_cnt;
+	if (qla_get_iocbs(sp->qpair, &sp->iores))
+		goto queuing_error;
+
 	if (req->cnt < (req_cnt + 2)) {
 		cnt = IS_SHADOW_REG_CAPABLE(ha) ? *req->out_ptr :
 		    rd_reg_dword_relaxed(req->req_q_out);
@@ -1709,6 +1715,7 @@ queuing_error:
 	if (tot_dsds)
 		scsi_dma_unmap(cmd);
 
+	qla_put_iocbs(sp->qpair, &sp->iores);
 	spin_unlock_irqrestore(&ha->hardware_lock, flags);
 
 	return QLA_FUNCTION_FAILED;
@@ -1822,6 +1829,12 @@ qla24xx_dif_start_scsi(srb_t *sp)
 	/* Total Data and protection sg segment(s) */
 	tot_prot_dsds = nseg;
 	tot_dsds += nseg;
+
+	sp->iores.res_type = RESOURCE_INI;
+	sp->iores.iocb_cnt = qla24xx_calc_iocbs(vha, tot_dsds);
+	if (qla_get_iocbs(sp->qpair, &sp->iores))
+		goto queuing_error;
+
 	if (req->cnt < (req_cnt + 2)) {
 		cnt = IS_SHADOW_REG_CAPABLE(ha) ? *req->out_ptr :
 		    rd_reg_dword_relaxed(req->req_q_out);
@@ -1896,6 +1909,7 @@ queuing_error:
 	}
 	/* Cleanup will be performed by the caller (queuecommand) */
 
+	qla_put_iocbs(sp->qpair, &sp->iores);
 	spin_unlock_irqrestore(&ha->hardware_lock, flags);
 	return QLA_FUNCTION_FAILED;
 }
@@ -1957,6 +1971,12 @@ qla2xxx_start_scsi_mq(srb_t *sp)
 
 	tot_dsds = nseg;
 	req_cnt = qla24xx_calc_iocbs(vha, tot_dsds);
+
+	sp->iores.res_type = RESOURCE_INI;
+	sp->iores.iocb_cnt = req_cnt;
+	if (qla_get_iocbs(sp->qpair, &sp->iores))
+		goto queuing_error;
+
 	if (req->cnt < (req_cnt + 2)) {
 		cnt = IS_SHADOW_REG_CAPABLE(ha) ? *req->out_ptr :
 		    rd_reg_dword_relaxed(req->req_q_out);
@@ -2029,6 +2049,7 @@ queuing_error:
 	if (tot_dsds)
 		scsi_dma_unmap(cmd);
 
+	qla_put_iocbs(sp->qpair, &sp->iores);
 	spin_unlock_irqrestore(&qpair->qp_lock, flags);
 
 	return QLA_FUNCTION_FAILED;
@@ -2157,6 +2178,12 @@ qla2xxx_dif_start_scsi_mq(srb_t *sp)
 	/* Total Data and protection sg segment(s) */
 	tot_prot_dsds = nseg;
 	tot_dsds += nseg;
+
+	sp->iores.res_type = RESOURCE_INI;
+	sp->iores.iocb_cnt = qla24xx_calc_iocbs(vha, tot_dsds);
+	if (qla_get_iocbs(sp->qpair, &sp->iores))
+		goto queuing_error;
+
 	if (req->cnt < (req_cnt + 2)) {
 		cnt = IS_SHADOW_REG_CAPABLE(ha) ? *req->out_ptr :
 		    rd_reg_dword_relaxed(req->req_q_out);
@@ -2234,6 +2261,7 @@ queuing_error:
 	}
 	/* Cleanup will be performed by the caller (queuecommand) */
 
+	qla_put_iocbs(sp->qpair, &sp->iores);
 	spin_unlock_irqrestore(&qpair->qp_lock, flags);
 	return QLA_FUNCTION_FAILED;
 }

drivers/scsi/qla2xxx/qla_isr.c

@@ -2901,6 +2901,7 @@ qla2x00_status_entry(scsi_qla_host_t *vha, struct rsp_que *rsp, void *pkt)
 		}
 		return;
 	}
+	qla_put_iocbs(sp->qpair, &sp->iores);
 
 	if (sp->cmd_type != TYPE_SRB) {
 		req->outstanding_cmds[handle] = NULL;
@@ -3313,6 +3314,7 @@ qla2x00_error_entry(scsi_qla_host_t *vha, struct rsp_que *rsp, sts_entry_t *pkt)
 	default:
 		sp = qla2x00_get_sp_from_handle(vha, func, req, pkt);
 		if (sp) {
+			qla_put_iocbs(sp->qpair, &sp->iores);
 			sp->done(sp, res);
 			return 0;
 		}

drivers/scsi/qla2xxx/qla_os.c

@@ -40,6 +40,11 @@ module_param(ql2xfulldump_on_mpifail, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(ql2xfulldump_on_mpifail,
 		 "Set this to take full dump on MPI hang.");
 
+int ql2xenforce_iocb_limit = 1;
+module_param(ql2xenforce_iocb_limit, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(ql2xenforce_iocb_limit,
+		 "Enforce IOCB throttling, to avoid FW congestion. (default: 0)");
+
 /*
  * CT6 CTX allocation cache
  */
@@ -3316,6 +3321,7 @@ qla2x00_probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
 		for (i = 0; i < ha->max_qpairs; i++)
 			qla2xxx_create_qpair(base_vha, 5, 0, startit);
 	}
+	qla_init_iocb_limit(base_vha);
 
 	if (ha->flags.running_gold_fw)
 		goto skip_dpc;