scsi: scsi_transport_fc: Add a max_bsg_segments field to struct fc_function_template

ibmvfc only supports a single segment for BSG FC passthrough.  Instead of
having it set a queue limits after creating the BSG queues, add a field so
that the FC transport can set it before allocating the queue.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240409143748.980206-6-hch@lst.deReviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ibmvscsi/ibmvfc.c

@@ -5541,8 +5541,6 @@ static void ibmvfc_tgt_add_rport(struct ibmvfc_target *tgt)
 			rport->supported_classes |= FC_COS_CLASS2;
 		if (be32_to_cpu(tgt->service_parms.class3_parms[0]) & 0x80000000)
 			rport->supported_classes |= FC_COS_CLASS3;
-		if (rport->rqst_q)
-			blk_queue_max_segments(rport->rqst_q, 1);
 	} else
 		tgt_dbg(tgt, "rport add failed\n");
 	spin_unlock_irqrestore(vhost->host->host_lock, flags);
@@ -6391,8 +6389,6 @@ static int ibmvfc_probe(struct vio_dev *vdev, const struct vio_device_id *id)
 
 	ibmvfc_init_sub_crqs(vhost);
 
-	if (shost_to_fc_host(shost)->rqst_q)
-		blk_queue_max_segments(shost_to_fc_host(shost)->rqst_q, 1);
 	dev_set_drvdata(dev, vhost);
 	spin_lock(&ibmvfc_driver_lock);
 	list_add_tail(&vhost->queue, &ibmvfc_head);
@@ -6547,6 +6543,7 @@ static struct fc_function_template ibmvfc_transport_functions = {
 	.get_starget_port_id = ibmvfc_get_starget_port_id,
 	.show_starget_port_id = 1,
 
+	.max_bsg_segments = 1,
 	.bsg_request = ibmvfc_bsg_request,
 	.bsg_timeout = ibmvfc_bsg_timeout,
 };

drivers/scsi/scsi_transport_fc.c

@@ -4288,6 +4288,7 @@ fc_bsg_hostadd(struct Scsi_Host *shost, struct fc_host_attrs *fc_host)
 	snprintf(bsg_name, sizeof(bsg_name),
 		 "fc_host%d", shost->host_no);
 	scsi_init_limits(shost, &lim);
+	lim.max_segments = min_not_zero(lim.max_segments, i->f->max_bsg_segments);
 	q = bsg_setup_queue(dev, bsg_name, &lim, fc_bsg_dispatch,
 			fc_bsg_job_timeout, i->f->dd_bsg_size);
 	if (IS_ERR(q)) {
@@ -4320,6 +4321,7 @@ fc_bsg_rportadd(struct Scsi_Host *shost, struct fc_rport *rport)
 		return -ENOTSUPP;
 
 	scsi_init_limits(shost, &lim);
+	lim.max_segments = min_not_zero(lim.max_segments, i->f->max_bsg_segments);
 	q = bsg_setup_queue(dev, dev_name(dev), &lim, fc_bsg_dispatch_prep,
 				fc_bsg_job_timeout, i->f->dd_bsg_size);
 	if (IS_ERR(q)) {

include/scsi/scsi_transport_fc.h

@@ -709,6 +709,7 @@ struct fc_function_template {
 	int  	(*vport_delete)(struct fc_vport *);
 
 	/* bsg support */
+	u32				max_bsg_segments;
 	int	(*bsg_request)(struct bsg_job *);
 	int	(*bsg_timeout)(struct bsg_job *);