net: ethtool: move checks before rtnl_lock() in ethnl_set_rings

Currently these two checks in ethnl_set_rings are added after rtnl_lock()
which will do useless works if the request is invalid.

So this patch moves these checks before the rtnl_lock() to avoid these
costs.
Signed-off-by: Jie Wang <wangjie125@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ethtool/rings.c

@@ -152,6 +152,24 @@ int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info)
 	if (!ops->get_ringparam || !ops->set_ringparam)
 		goto out_dev;
 
+	if (tb[ETHTOOL_A_RINGS_RX_BUF_LEN] &&
+	    !(ops->supported_ring_params & ETHTOOL_RING_USE_RX_BUF_LEN)) {
+		ret = -EOPNOTSUPP;
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    tb[ETHTOOL_A_RINGS_RX_BUF_LEN],
+				    "setting rx buf len not supported");
+		goto out_dev;
+	}
+
+	if (tb[ETHTOOL_A_RINGS_CQE_SIZE] &&
+	    !(ops->supported_ring_params & ETHTOOL_RING_USE_CQE_SIZE)) {
+		ret = -EOPNOTSUPP;
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    tb[ETHTOOL_A_RINGS_CQE_SIZE],
+				    "setting cqe size not supported");
+		goto out_dev;
+	}
+
 	if (tb[ETHTOOL_A_RINGS_TX_PUSH] &&
 	    !(ops->supported_ring_params & ETHTOOL_RING_USE_TX_PUSH)) {
 		ret = -EOPNOTSUPP;
@@ -201,24 +219,6 @@ int ethnl_set_rings(struct sk_buff *skb, struct genl_info *info)
 		goto out_ops;
 	}
 
-	if (kernel_ringparam.rx_buf_len != 0 &&
-	    !(ops->supported_ring_params & ETHTOOL_RING_USE_RX_BUF_LEN)) {
-		ret = -EOPNOTSUPP;
-		NL_SET_ERR_MSG_ATTR(info->extack,
-				    tb[ETHTOOL_A_RINGS_RX_BUF_LEN],
-				    "setting rx buf len not supported");
-		goto out_ops;
-	}
-
-	if (kernel_ringparam.cqe_size &&
-	    !(ops->supported_ring_params & ETHTOOL_RING_USE_CQE_SIZE)) {
-		ret = -EOPNOTSUPP;
-		NL_SET_ERR_MSG_ATTR(info->extack,
-				    tb[ETHTOOL_A_RINGS_CQE_SIZE],
-				    "setting cqe size not supported");
-		goto out_ops;
-	}
-
 	ret = dev->ethtool_ops->set_ringparam(dev, &ringparam,
 					      &kernel_ringparam, info->extack);
 	if (ret < 0)