gve: Alloc before freeing when changing features

Previously, existing queues were being freed before the resources for
the new queues were being allocated. This would take down the interface
if someone were to attempt to change feature flags under a resource
crunch.

Signed-off-by: Shailend Chand <shailend@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Jeroen de Borst <jeroendb@google.com>
Link: https://lore.kernel.org/r/20240122182632.1102721-7-shailend@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/google/gve/gve_main.c

@@ -2069,36 +2069,37 @@ static int gve_set_features(struct net_device *netdev,
 			    netdev_features_t features)
 {
 	const netdev_features_t orig_features = netdev->features;
+	struct gve_tx_alloc_rings_cfg tx_alloc_cfg = {0};
+	struct gve_rx_alloc_rings_cfg rx_alloc_cfg = {0};
+	struct gve_qpls_alloc_cfg qpls_alloc_cfg = {0};
 	struct gve_priv *priv = netdev_priv(netdev);
+	struct gve_qpl_config new_qpl_cfg;
 	int err;
 
+	gve_get_curr_alloc_cfgs(priv, &qpls_alloc_cfg,
+				&tx_alloc_cfg, &rx_alloc_cfg);
+	/* qpl_cfg is not read-only, it contains a map that gets updated as
+	 * rings are allocated, which is why we cannot use the yet unreleased
+	 * one in priv.
+	 */
+	qpls_alloc_cfg.qpl_cfg = &new_qpl_cfg;
+	tx_alloc_cfg.qpl_cfg = &new_qpl_cfg;
+	rx_alloc_cfg.qpl_cfg = &new_qpl_cfg;
+
 	if ((netdev->features & NETIF_F_LRO) != (features & NETIF_F_LRO)) {
 		netdev->features ^= NETIF_F_LRO;
 		if (netif_carrier_ok(netdev)) {
-			/* To make this process as simple as possible we
-			 * teardown the device, set the new configuration,
-			 * and then bring the device up again.
-			 */
-			err = gve_close(netdev);
-			/* We have already tried to reset in close, just fail
-			 * at this point.
-			 */
-			if (err)
-				goto err;
-
-			err = gve_open(netdev);
-			if (err)
-				goto err;
+			err = gve_adjust_config(priv, &qpls_alloc_cfg,
+						&tx_alloc_cfg, &rx_alloc_cfg);
+			if (err) {
+				/* Revert the change on error. */
+				netdev->features = orig_features;
+				return err;
+			}
 		}
 	}
 
 	return 0;
-err:
-	/* Reverts the change on error. */
-	netdev->features = orig_features;
-	netif_err(priv, drv, netdev,
-		  "Set features failed! !!! DISABLING ALL QUEUES !!!\n");
-	return err;
 }
 
 static const struct net_device_ops gve_netdev_ops = {