bdi: add error handle for bdi_debug_register

In order to make error handle more cleaner we call bdi_debug_register
before set state to WB_registered, that we can avoid call bdi_unregister
in release_bdi().
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: Nweiping zhang <zhangweiping@didichuxing.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

mm/backing-dev.c

@@ -882,10 +882,13 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
 	if (IS_ERR(dev))
 		return PTR_ERR(dev);
 
+	if (bdi_debug_register(bdi, dev_name(dev))) {
+		device_destroy(bdi_class, dev->devt);
+		return -ENOMEM;
+	}
 	cgwb_bdi_register(bdi);
 	bdi->dev = dev;
 
-	bdi_debug_register(bdi, dev_name(dev));
 	set_bit(WB_registered, &bdi->wb.state);
 
 	spin_lock_bh(&bdi_lock);