scsi: core: Make the budget map optional

Prepare for not allocating a budget map for pseudo SCSI devices by
checking whether a budget map has been allocated before using it.

Reviewed-by: Hannes Reinecke <[e-mail]>
Cc: John Garry <[e-mail]>
Cc: Ming Lei <[e-mail]>
Signed-off-by: Bart Van Assche <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/scsi.c

···
  */
 int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
 {
+	if (!sdev->budget_map.map)
+		return -EINVAL;
+
 	depth = min_t(int, depth, scsi_device_max_queue_depth(sdev));
 
 	if (depth > 0) {
···
  */
 int scsi_track_queue_full(struct scsi_device *sdev, int depth)
 {
+	if (!sdev->budget_map.map)
+		return 0;
 
 	/*
 	 * Don't let QUEUE_FULLs on the same

drivers/scsi/scsi_error.c

···
 	const struct scsi_host_template *sht = sdev->host->hostt;
 	struct scsi_device *tmp_sdev;
 
+	if (!sdev->budget_map.map)
+		return;
+
 	if (!sht->track_queue_depth ||
 	    sdev->queue_depth >= sdev->max_queue_depth)
 		return;

drivers/scsi/scsi_lib.c

···
 	if (starget->can_queue > 0)
 		atomic_dec(&starget->target_busy);
 
-	sbitmap_put(&sdev->budget_map, cmd->budget_token);
+	if (sdev->budget_map.map)
+		sbitmap_put(&sdev->budget_map, cmd->budget_token);
 	cmd->budget_token = -1;
 }
 
···
 {
 	int token;
 
+	if (!sdev->budget_map.map)
+		return INT_MAX;
+
 	token = sbitmap_get(&sdev->budget_map);
 	if (token < 0)
 		return -1;
···
 {
 	struct scsi_device *sdev = q->queuedata;
 
-	sbitmap_put(&sdev->budget_map, budget_token);
+	if (sdev->budget_map.map)
+		sbitmap_put(&sdev->budget_map, budget_token);
 }
 
 /*