nvme: inherit stable pages constraint in the mpath stack device

If the backing device require stable pages, we need to set it on the
stack mpath device as well. This applies to rdma/fc transports when
doing data integrity and tcp transport calculating digests.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -1897,6 +1897,13 @@ static void __nvme_revalidate_disk(struct gendisk *disk, struct nvme_id_ns *id)
 	if (ns->head->disk) {
 		nvme_update_disk_info(ns->head->disk, ns, id);
 		blk_queue_stack_limits(ns->head->disk->queue, ns->queue);
+		if (bdi_cap_stable_pages_required(ns->queue->backing_dev_info)) {
+			struct backing_dev_info *info =
+				ns->head->disk->queue->backing_dev_info;
+
+                        info->capabilities |= BDI_CAP_STABLE_WRITES;
+		}
+
 		revalidate_disk(ns->head->disk);
 	}
 #endif