nvmet: only check for filebacking on -ENOTBLK

We only need to check for a file-backed namespace if
nvmet_bdev_ns_enable() returns -ENOTBLK. For any other error
it's pointless as the open() error will remain the same.

Fixes: d5eff33 ("nvmet: add simple file backed ns support")
Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/core.c

@@ -339,7 +339,7 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
 		goto out_unlock;
 
 	ret = nvmet_bdev_ns_enable(ns);
-	if (ret)
+	if (ret == -ENOTBLK)
 		ret = nvmet_file_ns_enable(ns);
 	if (ret)
 		goto out_unlock;