dm mpath: eliminate need to use scsi_device_from_queue

Instead of scsi_device_from_queue(), use scsi_dh_attached_handler_name()
-- whose implementation uses scsi_device_from_queue() to avoid trying to
access SCSI-specific resources from non-SCSI devices.

Fixes buildbot reported issue when CONFIG_SCSI isn't set:
 ERROR: "scsi_device_from_queue" [drivers/md/dm-multipath.ko] undefined!

Fixes: 8d47e659 ("dm mpath: remove unnecessary NVMe branching in favor of scsi_dh checks")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-mpath.c

@@ -22,7 +22,6 @@
 #include <linux/time.h>
 #include <linux/workqueue.h>
 #include <linux/delay.h>
-#include <scsi/scsi_device.h>
 #include <scsi/scsi_dh.h>
 #include <linux/atomic.h>
 #include <linux/blk-mq.h>
@@ -805,15 +804,14 @@ static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 	return 0;
 }
 
-static int setup_scsi_dh(struct block_device *bdev, struct multipath *m, char **error)
+static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
+			 const char *attached_handler_name, char **error)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
-	const char *attached_handler_name;
 	int r;
 
 	if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 retain:
-		attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 		if (attached_handler_name) {
 			/*
 			 * Clear any hw_handler_params associated with a
@@ -867,7 +865,8 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
 	int r;
 	struct pgpath *p;
 	struct multipath *m = ti->private;
-	struct scsi_device *sdev;
+	struct request_queue *q;
+	const char *attached_handler_name;
 
 	/* we need at least a path arg */
 	if (as->argc < 1) {
@@ -886,11 +885,11 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps
 		goto bad;
 	}
 
-	sdev = scsi_device_from_queue(bdev_get_queue(p->path.dev->bdev));
-	if (sdev) {
-		put_device(&sdev->sdev_gendev);
+	q = bdev_get_queue(p->path.dev->bdev);
+	attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
+	if (attached_handler_name) {
 		INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
-		r = setup_scsi_dh(p->path.dev->bdev, m, &ti->error);
+		r = setup_scsi_dh(p->path.dev->bdev, m, attached_handler_name, &ti->error);
 		if (r) {
 			dm_put_device(ti, p->path.dev);
 			goto bad;