lightnvm: prematurely activate nvm_dev

We register with nvm_devices when there registration can still fail.
Move the final registration at the end of the nvm_register function
to make sure we are fully registered when added to the nvm_devices list.
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/core.c

@@ -318,10 +318,6 @@ int nvm_register(struct request_queue *q, char *disk_name,
 	if (ret)
 		goto err_init;
 
-	down_write(&nvm_lock);
-	list_add(&dev->devices, &nvm_devices);
-	up_write(&nvm_lock);
-
 	if (dev->ops->max_phys_sect > 1) {
 		dev->ppalist_pool = dev->ops->create_dma_pool(dev->q,
 								"ppalist");
@@ -334,6 +330,10 @@ int nvm_register(struct request_queue *q, char *disk_name,
 		return -EINVAL;
 	}
 
+	down_write(&nvm_lock);
+	list_add(&dev->devices, &nvm_devices);
+	up_write(&nvm_lock);
+
 	return 0;
 err_init:
 	kfree(dev);