nbd: fix -ERESTARTSYS handling

Christoph made it so that if we return'ed BLK_STS_RESOURCE whenever we
got ERESTARTSYS from sending our packets we'd return BLK_STS_OK, which
means we'd never requeue and just hang.  We really need to return the
right value from the upper layer.

Fixes: fc17b6534eb8 ("blk-mq: switch ->queue_rq return value to blk_status_t")
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/nbd.c

@@ -820,9 +820,13 @@ static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
 	 * appropriate.
 	 */
 	ret = nbd_handle_cmd(cmd, hctx->queue_num);
+	if (ret < 0)
+		ret = BLK_STS_IOERR;
+	else if (!ret)
+		ret = BLK_STS_OK;
 	complete(&cmd->send_complete);
 
-	return ret < 0 ? BLK_STS_IOERR : BLK_STS_OK;
+	return ret;
 }
 
 static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,