scsi: qla2xxx: Fix crash due to mismatch mumber of Q-pair creation for Multi queue

commit b95b9452 upstream.

when driver is loaded with Multi Queue enabled, it was noticed that
there was one less queue pair created.

Following message would indicate this:

"No resources to create additional q pair."

The result of one less queue pair means that system can crash, if the
block mq layer thinks there is an extra hardware queue available, and
the driver will use a NULL ptr qpair in that instance.

Following stack trace is seen in one of the crash:

irq_create_affinity_masks+0x98/0x530
irq_create_affinity_masks+0x98/0x530
__pci_enable_msix+0x321/0x4e0
mutex_lock+0x12/0x40
pci_alloc_irq_vectors_affinity+0xb5/0x140
qla24xx_enable_msix+0x79/0x530 [qla2xxx]
qla2x00_request_irqs+0x61/0x2d0 [qla2xxx]
qla2x00_probe_one+0xc73/0x2390 [qla2xxx]
ida_simple_get+0x98/0x100
kernfs_next_descendant_post+0x40/0x50
local_pci_probe+0x45/0xa0
pci_device_probe+0xfc/0x140
driver_probe_device+0x2c5/0x470
__driver_attach+0xdd/0xe0
driver_probe_device+0x470/0x470
bus_for_each_dev+0x6c/0xc0
driver_attach+0x1e/0x20
bus_add_driver+0x45/0x270
driver_register+0x60/0xe0
__pci_register_driver+0x4c/0x50
qla2x00_module_init+0x1ce/0x21e [qla2xxx]
Signed-off-by: Sawan Chandak <sawan.chandak@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/scsi/qla2xxx/qla_def.h

@@ -3425,6 +3425,7 @@ struct qla_hw_data {
 	uint8_t 	max_req_queues;
 	uint8_t 	max_rsp_queues;
 	uint8_t		max_qpairs;
+	uint8_t		num_qpairs;
 	struct qla_qpair *base_qpair;
 	struct qla_npiv_entry *npiv_info;
 	uint16_t	nvram_npiv_size;

drivers/scsi/qla2xxx/qla_init.c

@@ -7543,12 +7543,13 @@ struct qla_qpair *qla2xxx_create_qpair(struct scsi_qla_host *vha, int qos, int v
 		/* Assign available que pair id */
 		mutex_lock(&ha->mq_lock);
 		qpair_id = find_first_zero_bit(ha->qpair_qid_map, ha->max_qpairs);
-		if (qpair_id >= ha->max_qpairs) {
+		if (ha->num_qpairs >= ha->max_qpairs) {
 			mutex_unlock(&ha->mq_lock);
 			ql_log(ql_log_warn, vha, 0x0183,
 			    "No resources to create additional q pair.\n");
 			goto fail_qid_map;
 		}
+		ha->num_qpairs++;
 		set_bit(qpair_id, ha->qpair_qid_map);
 		ha->queue_pair_map[qpair_id] = qpair;
 		qpair->id = qpair_id;
@@ -7635,6 +7636,7 @@ struct qla_qpair *qla2xxx_create_qpair(struct scsi_qla_host *vha, int qos, int v
 fail_msix:
 	ha->queue_pair_map[qpair_id] = NULL;
 	clear_bit(qpair_id, ha->qpair_qid_map);
+	ha->num_qpairs--;
 	mutex_unlock(&ha->mq_lock);
 fail_qid_map:
 	kfree(qpair);
@@ -7660,6 +7662,7 @@ int qla2xxx_delete_qpair(struct scsi_qla_host *vha, struct qla_qpair *qpair)
 	mutex_lock(&ha->mq_lock);
 	ha->queue_pair_map[qpair->id] = NULL;
 	clear_bit(qpair->id, ha->qpair_qid_map);
+	ha->num_qpairs--;
 	list_del(&qpair->qp_list_elem);
 	if (list_empty(&vha->qp_list))
 		vha->flags.qpairs_available = 0;