net: openvswitch: shrink the mask array if necessary

When creating and inserting flow-mask, if there is no available
flow-mask, we realloc the mask array. When removing flow-mask,
if necessary, we shrink mask array.
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Tested-by: Greg Rose <gvrose8192@gmail.com>
Acked-by: William Tu <u9012063@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/flow_table.c

@@ -694,6 +694,23 @@ static struct table_instance *table_instance_expand(struct table_instance *ti,
 	return table_instance_rehash(ti, ti->n_buckets * 2, ufid);
 }
 
+static void tbl_mask_array_delete_mask(struct mask_array *ma,
+				       struct sw_flow_mask *mask)
+{
+	int i;
+
+	/* Remove the deleted mask pointers from the array */
+	for (i = 0; i < ma->max; i++) {
+		if (mask == ovsl_dereference(ma->masks[i])) {
+			RCU_INIT_POINTER(ma->masks[i], NULL);
+			ma->count--;
+			kfree_rcu(mask, rcu);
+			return;
+		}
+	}
+	BUG();
+}
+
 /* Remove 'mask' from the mask list, if it is not needed any more. */
 static void flow_mask_remove(struct flow_table *tbl, struct sw_flow_mask *mask)
 {
@@ -707,18 +724,14 @@ static void flow_mask_remove(struct flow_table *tbl, struct sw_flow_mask *mask)
 
 		if (!mask->ref_count) {
 			struct mask_array *ma;
-			int i;
 
 			ma = ovsl_dereference(tbl->mask_array);
-			for (i = 0; i < ma->max; i++) {
-				if (mask == ovsl_dereference(ma->masks[i])) {
-					RCU_INIT_POINTER(ma->masks[i], NULL);
-					ma->count--;
-					kfree_rcu(mask, rcu);
-					return;
-				}
-			}
-			BUG();
+			tbl_mask_array_delete_mask(ma, mask);
+
+			/* Shrink the mask array if necessary. */
+			if (ma->max >= (MASK_ARRAY_SIZE_MIN * 2) &&
+			    ma->count <= (ma->max / 3))
+				tbl_mask_array_realloc(tbl, ma->max / 2);
 		}
 	}
 }