net: add an helper to copy xps maps to the new dev_maps

This patch adds an helper, xps_copy_dev_maps, to copy maps from dev_maps
to new_dev_maps at a given index. The logic should be the same, with an
improved code readability and maintenance.
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -2608,6 +2608,25 @@ static struct xps_map *expand_xps_map(struct xps_map *map, int attr_index,
 	return new_map;
 }
 
+/* Copy xps maps at a given index */
+static void xps_copy_dev_maps(struct xps_dev_maps *dev_maps,
+			      struct xps_dev_maps *new_dev_maps, int index,
+			      int tc, bool skip_tc)
+{
+	int i, tci = index * dev_maps->num_tc;
+	struct xps_map *map;
+
+	/* copy maps belonging to foreign traffic classes */
+	for (i = 0; i < dev_maps->num_tc; i++, tci++) {
+		if (i == tc && skip_tc)
+			continue;
+
+		/* fill in the new device map from the old device map */
+		map = xmap_dereference(dev_maps->attr_map[tci]);
+		RCU_INIT_POINTER(new_dev_maps->attr_map[tci], map);
+	}
+}
+
 /* Must be called under cpus_read_lock */
 int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 			  u16 index, enum xps_map_type type)
@@ -2694,23 +2713,16 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 	}
 
 	for (j = 0; j < nr_ids; j++) {
-		/* copy maps belonging to foreign traffic classes */
-		for (i = tc, tci = j * num_tc; copy && i--; tci++) {
-			/* fill in the new device map from the old device map */
-			map = xmap_dereference(dev_maps->attr_map[tci]);
-			RCU_INIT_POINTER(new_dev_maps->attr_map[tci], map);
-		}
+		bool skip_tc = false;
 
-		/* We need to explicitly update tci as prevous loop
-		 * could break out early if dev_maps is NULL.
-		 */
 		tci = j * num_tc + tc;
-
 		if (netif_attr_test_mask(j, mask, nr_ids) &&
 		    netif_attr_test_online(j, online_mask, nr_ids)) {
 			/* add tx-queue to CPU/rx-queue maps */
 			int pos = 0;
 
+			skip_tc = true;
+
 			map = xmap_dereference(new_dev_maps->attr_map[tci]);
 			while ((pos < map->len) && (map->queues[pos] != index))
 				pos++;
@@ -2725,18 +2737,11 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 					numa_node_id = -1;
 			}
 #endif
-		} else if (copy) {
-			/* fill in the new device map from the old device map */
-			map = xmap_dereference(dev_maps->attr_map[tci]);
-			RCU_INIT_POINTER(new_dev_maps->attr_map[tci], map);
 		}
 
-		/* copy maps belonging to foreign traffic classes */
-		for (i = num_tc - tc, tci++; copy && --i; tci++) {
-			/* fill in the new device map from the old device map */
-			map = xmap_dereference(dev_maps->attr_map[tci]);
-			RCU_INIT_POINTER(new_dev_maps->attr_map[tci], map);
-		}
+		if (copy)
+			xps_copy_dev_maps(dev_maps, new_dev_maps, j, tc,
+					  skip_tc);
 	}
 
 	rcu_assign_pointer(dev->xps_maps[type], new_dev_maps);