Fix to return error code -ENOMEM from the null_alloc_dev() error
handling case instead of 0, as done elsewhere in this function.
Fixes: 2984c8684f96 ("nullb: factor disk parameters")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
 
        for (i = 0; i < nr_devices; i++) {
                dev = null_alloc_dev();
-               if (!dev)
+               if (!dev) {
+                       ret = -ENOMEM;
                        goto err_dev;
+               }
                ret = null_add_dev(dev);
                if (ret) {
                        null_free_dev(dev);