Gas limit ceiling option.

parity/cli.rs

@@ -137,6 +137,8 @@ Sealing/Mining Options:
                            good value [default: auto].
   --gas-floor-target GAS   Amount of gas per block to target when sealing a new
                            block [default: 3141592].
+  --gas-cap GAS            A cap on how large we will raise the gas limit per
+                           block due to transaction volume [default: 3141592].
   --author ADDRESS         Specify the block author (aka "coinbase") address
                            for sending block rewards from sealed blocks
                            [default: 0037a6b811ffeb6e072da21179d11b1406371c63].
@@ -283,6 +285,7 @@ pub struct Args {
 	pub flag_usd_per_tx: String,
 	pub flag_usd_per_eth: String,
 	pub flag_gas_floor_target: String,
+	pub flag_gas_cap: String,
 	pub flag_extra_data: Option<String>,
 	pub flag_tx_limit: usize,
 	pub flag_logging: Option<String>,

parity/configuration.rs

@@ -85,7 +85,16 @@ impl Configuration {
 		}
 	}
 
-
+	pub fn gas_ceil_target(&self) -> U256 {
+		if self.args.flag_dont_help_rescue_dao || self.args.flag_dogmatic {
+			10_000_000.into()
+		} else {
+			let d = &self.args.flag_gas_cap;
+			U256::from_dec_str(d).unwrap_or_else(|_| {
+				die!("{}: Invalid target gas ceiling given. Must be a decimal unsigned 256-bit number.", d)
+			})
+		}
+	}
 
 	pub fn gas_price(&self) -> U256 {
 		match self.args.flag_gasprice.as_ref() {

parity/main.rs

@@ -211,6 +211,7 @@ fn execute_client(conf: Configuration, spec: Spec, client_config: ClientConfig)
 	let miner = Miner::with_accounts(conf.args.flag_force_sealing, conf.spec(), account_service.clone());
 	miner.set_author(conf.author());
 	miner.set_gas_floor_target(conf.gas_floor_target());
+	miner.set_gas_ceil_target(conf.gas_ceil_target());
 	miner.set_extra_data(conf.extra_data());
 	miner.set_minimal_gas_price(conf.gas_price());
 	miner.set_transactions_limit(conf.args.flag_tx_limit);