batman-adv: Replace gw_reselect divisor with simple shift

The gw_factor is divided by BATADV_TQ_LOCAL_WINDOW_SIZE ** 2 * 64. But the
rest of the calculation has nothing to do with the tq window size and
therefore the calculation is just (tmp_gw_factor / (64 ** 3)).

Replace it with a simple shift to avoid a costly 64-bit divide when the
max_gw_factor is changed from u32 to u64. This type change is necessary
to avoid an overflow bug.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index bb01586..e1e1f31 100644 (file)
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -154,14 +154,10 @@ batadv_gw_get_best_gw_node(struct batadv_priv *bat_priv)
        struct batadv_neigh_ifinfo *router_ifinfo;
        struct batadv_gw_node *gw_node, *curr_gw = NULL;
        uint32_t max_gw_factor = 0, tmp_gw_factor = 0;
-       uint32_t gw_divisor;
        uint8_t max_tq = 0;
        uint8_t tq_avg;
        struct batadv_orig_node *orig_node;
 
-       gw_divisor = BATADV_TQ_LOCAL_WINDOW_SIZE * BATADV_TQ_LOCAL_WINDOW_SIZE;
-       gw_divisor *= 64;
-
        rcu_read_lock();
        hlist_for_each_entry_rcu(gw_node, &bat_priv->gw.list, list) {
                if (gw_node->deleted)
@@ -187,7 +183,7 @@ batadv_gw_get_best_gw_node(struct batadv_priv *bat_priv)
                        tmp_gw_factor = tq_avg * tq_avg;
                        tmp_gw_factor *= gw_node->bandwidth_down;
                        tmp_gw_factor *= 100 * 100;
-                       tmp_gw_factor /= gw_divisor;
+                       tmp_gw_factor >>= 18;
 
                        if ((tmp_gw_factor > max_gw_factor) ||
                            ((tmp_gw_factor == max_gw_factor) &&