scsi: smartpqi: Convert to host_tagset

Add support for host_tagset.

Also move the reserved command slots to the end of the pool to eliminate an
addition operation for every SCSI request.

This patch was originally authored by Hannes Reinecke here:

Link: https://lore.kernel.org/linux-block/20191126131009.71726-8-hare@suse.de/

But we NAKed this patch because we wanted to fully test multipath
failover operations.
Suggested-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Scott Benesh <scott.benesh@microchip.com>
Reviewed-by: Scott Teel <scott.teel@microchip.com>
Reviewed-by: Mahesh Rajashekhara <Mahesh.Rajashekhara@microchip.com>
Reviewed-by: Mike McGowen <Mike.McGowen@microchip.com>
Reviewed-by: Kevin Barnett <kevin.barnett@microchip.com>
Signed-off-by: Don Brace <don.brace@microchip.com>
Link: https://lore.kernel.org/r/166793529811.322537.3294617845448383948.stgit@brunhildaSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/smartpqi/smartpqi.h

@@ -1307,7 +1307,6 @@ struct pqi_ctrl_info {
 	dma_addr_t	error_buffer_dma_handle;
 	size_t		sg_chain_buffer_length;
 	unsigned int	num_queue_groups;
-	u16		max_hw_queue_index;
 	u16		num_elements_per_iq;
 	u16		num_elements_per_oq;
 	u16		max_inbound_iu_length_per_firmware;
@@ -1369,8 +1368,6 @@ struct pqi_ctrl_info {
 	u64		sas_address;
 
 	struct pqi_io_request *io_request_pool;
-	u16		next_io_request_slot;
-
 	struct pqi_event events[PQI_NUM_SUPPORTED_EVENTS];
 	struct work_struct event_work;
 

drivers/scsi/smartpqi/smartpqi_init.c

@@ -678,22 +678,35 @@ static inline void pqi_reinit_io_request(struct pqi_io_request *io_request)
 	io_request->raid_bypass = false;
 }
 
-static struct pqi_io_request *pqi_alloc_io_request(
-	struct pqi_ctrl_info *ctrl_info)
+static inline struct pqi_io_request *pqi_alloc_io_request(struct pqi_ctrl_info *ctrl_info, struct scsi_cmnd *scmd)
 {
 	struct pqi_io_request *io_request;
-	u16 i = ctrl_info->next_io_request_slot;	/* benignly racy */
+	u16 i;
 
-	while (1) {
+	if (scmd) { /* SML I/O request */
+		u32 blk_tag = blk_mq_unique_tag(scsi_cmd_to_rq(scmd));
+
+		i = blk_mq_unique_tag_to_tag(blk_tag);
 		io_request = &ctrl_info->io_request_pool[i];
+		if (atomic_inc_return(&io_request->refcount) > 1) {
+			atomic_dec(&io_request->refcount);
+			return NULL;
+		}
+	} else { /* IOCTL or driver internal request */
+		/*
+		 * benignly racy - may have to wait for an open slot.
+		 * command slot range is scsi_ml_can_queue -
+		 *         [scsi_ml_can_queue + (PQI_RESERVED_IO_SLOTS - 1)]
+		 */
+		i = 0;
+		while (1) {
+			io_request = &ctrl_info->io_request_pool[ctrl_info->scsi_ml_can_queue + i];
 			if (atomic_inc_return(&io_request->refcount) == 1)
 				break;
 			atomic_dec(&io_request->refcount);
-		i = (i + 1) % ctrl_info->max_io_slots;
+			i = (i + 1) % PQI_RESERVED_IO_SLOTS;
+		}
 	}
-
-	/* benignly racy */
-	ctrl_info->next_io_request_slot = (i + 1) % ctrl_info->max_io_slots;
 
 	pqi_reinit_io_request(io_request);
 
@@ -4586,7 +4599,7 @@ static int pqi_submit_raid_request_synchronous(struct pqi_ctrl_info *ctrl_info,
 		goto out;
 	}
 
-	io_request = pqi_alloc_io_request(ctrl_info);
+	io_request = pqi_alloc_io_request(ctrl_info, NULL);
 
 	put_unaligned_le16(io_request->index,
 		&(((struct pqi_raid_path_request *)request)->request_id));
@@ -5233,7 +5246,6 @@ static void pqi_calculate_queue_resources(struct pqi_ctrl_info *ctrl_info)
 	}
 
 	ctrl_info->num_queue_groups = num_queue_groups;
-	ctrl_info->max_hw_queue_index = num_queue_groups - 1;
 
 	/*
 	 * Make sure that the max. inbound IU length is an even multiple
@@ -5567,7 +5579,9 @@ static inline int pqi_raid_submit_scsi_cmd(struct pqi_ctrl_info *ctrl_info,
 {
 	struct pqi_io_request *io_request;
 
-	io_request = pqi_alloc_io_request(ctrl_info);
+	io_request = pqi_alloc_io_request(ctrl_info, scmd);
+	if (!io_request)
+		return SCSI_MLQUEUE_HOST_BUSY;
 
 	return pqi_raid_submit_scsi_cmd_with_io_request(ctrl_info, io_request,
 		device, scmd, queue_group);
@@ -5671,7 +5685,9 @@ static int pqi_aio_submit_io(struct pqi_ctrl_info *ctrl_info,
 	struct pqi_scsi_dev *device;
 
 	device = scmd->device->hostdata;
-	io_request = pqi_alloc_io_request(ctrl_info);
+	io_request = pqi_alloc_io_request(ctrl_info, scmd);
+	if (!io_request)
+		return SCSI_MLQUEUE_HOST_BUSY;
 	io_request->io_complete_callback = pqi_aio_io_complete;
 	io_request->scmd = scmd;
 	io_request->raid_bypass = raid_bypass;
@@ -5743,7 +5759,10 @@ static  int pqi_aio_submit_r1_write_io(struct pqi_ctrl_info *ctrl_info,
 	struct pqi_io_request *io_request;
 	struct pqi_aio_r1_path_request *r1_request;
 
-	io_request = pqi_alloc_io_request(ctrl_info);
+	io_request = pqi_alloc_io_request(ctrl_info, scmd);
+	if (!io_request)
+		return SCSI_MLQUEUE_HOST_BUSY;
+
 	io_request->io_complete_callback = pqi_aio_io_complete;
 	io_request->scmd = scmd;
 	io_request->raid_bypass = true;
@@ -5801,7 +5820,9 @@ static int pqi_aio_submit_r56_write_io(struct pqi_ctrl_info *ctrl_info,
 	struct pqi_io_request *io_request;
 	struct pqi_aio_r56_path_request *r56_request;
 
-	io_request = pqi_alloc_io_request(ctrl_info);
+	io_request = pqi_alloc_io_request(ctrl_info, scmd);
+	if (!io_request)
+		return SCSI_MLQUEUE_HOST_BUSY;
 	io_request->io_complete_callback = pqi_aio_io_complete;
 	io_request->scmd = scmd;
 	io_request->raid_bypass = true;
@@ -5860,13 +5881,10 @@ static int pqi_aio_submit_r56_write_io(struct pqi_ctrl_info *ctrl_info,
 static inline u16 pqi_get_hw_queue(struct pqi_ctrl_info *ctrl_info,
 	struct scsi_cmnd *scmd)
 {
-	u16 hw_queue;
-
-	hw_queue = blk_mq_unique_tag_to_hwq(blk_mq_unique_tag(scsi_cmd_to_rq(scmd)));
-	if (hw_queue > ctrl_info->max_hw_queue_index)
-		hw_queue = 0;
-
-	return hw_queue;
+	/*
+	 * We are setting host_tagset = 1 during init.
+	 */
+	return blk_mq_unique_tag_to_hwq(blk_mq_unique_tag(scsi_cmd_to_rq(scmd)));
 }
 
 static inline bool pqi_is_bypass_eligible_request(struct scsi_cmnd *scmd)
@@ -6268,7 +6286,7 @@ static int pqi_lun_reset(struct pqi_ctrl_info *ctrl_info, struct scsi_cmnd *scmd
 	struct pqi_scsi_dev *device;
 
 	device = scmd->device->hostdata;
-	io_request = pqi_alloc_io_request(ctrl_info);
+	io_request = pqi_alloc_io_request(ctrl_info, NULL);
 	io_request->io_complete_callback = pqi_lun_reset_complete;
 	io_request->context = &wait;