nvme: send discovery log page change events to userspace

If the controller supports discovery log page change events,
we want to enable it. When we see a discovery log change event
we will send it up to userspace and expect it to handle it.
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/core.c

@@ -1185,7 +1185,8 @@ int nvme_set_queue_count(struct nvme_ctrl *ctrl, int *count)
 EXPORT_SYMBOL_GPL(nvme_set_queue_count);
 
 #define NVME_AEN_SUPPORTED \
-	(NVME_AEN_CFG_NS_ATTR | NVME_AEN_CFG_FW_ACT | NVME_AEN_CFG_ANA_CHANGE)
+	(NVME_AEN_CFG_NS_ATTR | NVME_AEN_CFG_FW_ACT | \
+	 NVME_AEN_CFG_ANA_CHANGE | NVME_AEN_CFG_DISC_CHANGE)
 
 static void nvme_enable_aen(struct nvme_ctrl *ctrl)
 {
@@ -3768,6 +3769,9 @@ static void nvme_handle_aen_notice(struct nvme_ctrl *ctrl, u32 result)
 		queue_work(nvme_wq, &ctrl->ana_work);
 		break;
 #endif
+	case NVME_AER_NOTICE_DISC_CHANGED:
+		ctrl->aen_result = result;
+		break;
 	default:
 		dev_warn(ctrl->device, "async event result %08x\n", result);
 	}