nvme-multipath: avoid crash on invalid subsystem cntlid enumeration

A process holding an open reference to a removed disk prevents it
from completing deletion, so its name continues to exist. A subsequent
gendisk creation may have the same cntlid which risks collision when
using that for the name. Use the unique ctrl->instance instead.
Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/multipath.c

@@ -31,7 +31,7 @@ void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
 		sprintf(disk_name, "nvme%dn%d", ctrl->instance, ns->head->instance);
 	} else if (ns->head->disk) {
 		sprintf(disk_name, "nvme%dc%dn%d", ctrl->subsys->instance,
-				ctrl->cntlid, ns->head->instance);
+				ctrl->instance, ns->head->instance);
 		*flags = GENHD_FL_HIDDEN;
 	} else {
 		sprintf(disk_name, "nvme%dn%d", ctrl->subsys->instance,