net: ena: avoid unnecessary admin command when RSS function set fails

Currently when ena_set_hash_function() fails the hash function is
restored to the previous value by calling an admin command to get
the hash function from the device.

In this commit we avoid the admin command, by saving the previous
hash function before calling ena_set_hash_function() and using this
previous value to restore the hash function in case of failure of
ena_set_hash_function().
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amazon/ena/ena_com.c

@@ -2286,6 +2286,7 @@ int ena_com_fill_hash_function(struct ena_com_dev *ena_dev,
 	struct ena_admin_get_feat_resp get_resp;
 	struct ena_admin_feature_rss_flow_hash_control *hash_key =
 		rss->hash_key;
+	enum ena_admin_hash_functions old_func;
 	int rc;
 
 	/* Make sure size is a mult of DWs */
@@ -2325,12 +2326,13 @@ int ena_com_fill_hash_function(struct ena_com_dev *ena_dev,
 		return -EINVAL;
 	}
 
+	old_func = rss->hash_func;
 	rss->hash_func = func;
 	rc = ena_com_set_hash_function(ena_dev);
 
 	/* Restore the old function */
 	if (unlikely(rc))
-		ena_com_get_hash_function(ena_dev, NULL, NULL);
+		rss->hash_func = old_func;
 
 	return rc;
 }