From 4ed3997938ad915004c500f6138fcee3d46112a8 Mon Sep 17 00:00:00 2001
From: ordian <write@reusable.software>
Date: Tue, 21 Mar 2023 17:20:59 +0100
Subject: [PATCH] runtime/inclusion: fix availability_threshold (#6931)
---
polkadot/primitives/src/v4/mod.rs | 4 ++--
polkadot/runtime/parachains/src/inclusion/mod.rs | 12 +++++-------
polkadot/runtime/parachains/src/inclusion/tests.rs | 7 +++++++
3 files changed, 14 insertions(+), 9 deletions(-)
diff --git a/polkadot/primitives/src/v4/mod.rs b/polkadot/primitives/src/v4/mod.rs
index efd6db836c2..4319aba53e1 100644
--- a/polkadot/primitives/src/v4/mod.rs
+++ b/polkadot/primitives/src/v4/mod.rs
@@ -1609,13 +1609,13 @@ where
/// The maximum number of validators `f` which may safely be faulty.
///
/// The total number of validators is `n = 3f + e` where `e in { 1, 2, 3 }`.
-pub fn byzantine_threshold(n: usize) -> usize {
+pub const fn byzantine_threshold(n: usize) -> usize {
n.saturating_sub(1) / 3
}
/// The supermajority threshold of validators which represents a subset
/// guaranteed to have at least f+1 honest validators.
-pub fn supermajority_threshold(n: usize) -> usize {
+pub const fn supermajority_threshold(n: usize) -> usize {
n - byzantine_threshold(n)
}
diff --git a/polkadot/runtime/parachains/src/inclusion/mod.rs b/polkadot/runtime/parachains/src/inclusion/mod.rs
index e2bd5f8511d..4f2f530e121 100644
--- a/polkadot/runtime/parachains/src/inclusion/mod.rs
+++ b/polkadot/runtime/parachains/src/inclusion/mod.rs
@@ -28,10 +28,10 @@ use bitvec::{order::Lsb0 as BitOrderLsb0, vec::BitVec};
use frame_support::pallet_prelude::*;
use parity_scale_codec::{Decode, Encode};
use primitives::{
- AvailabilityBitfield, BackedCandidate, CandidateCommitments, CandidateDescriptor,
- CandidateHash, CandidateReceipt, CommittedCandidateReceipt, CoreIndex, GroupIndex, Hash,
- HeadData, Id as ParaId, SigningContext, UncheckedSignedAvailabilityBitfields, ValidatorId,
- ValidatorIndex, ValidityAttestation,
+ supermajority_threshold, AvailabilityBitfield, BackedCandidate, CandidateCommitments,
+ CandidateDescriptor, CandidateHash, CandidateReceipt, CommittedCandidateReceipt, CoreIndex,
+ GroupIndex, Hash, HeadData, Id as ParaId, SigningContext, UncheckedSignedAvailabilityBitfields,
+ ValidatorId, ValidatorIndex, ValidityAttestation,
};
use scale_info::TypeInfo;
use sp_runtime::{traits::One, DispatchError};
@@ -899,9 +899,7 @@ impl<T: Config> Pallet<T> {
}
const fn availability_threshold(n_validators: usize) -> usize {
- let mut threshold = (n_validators * 2) / 3;
- threshold += (n_validators * 2) % 3;
- threshold
+ supermajority_threshold(n_validators)
}
#[derive(derive_more::From, Debug)]
diff --git a/polkadot/runtime/parachains/src/inclusion/tests.rs b/polkadot/runtime/parachains/src/inclusion/tests.rs
index 17ef7f7beac..e0b34125830 100644
--- a/polkadot/runtime/parachains/src/inclusion/tests.rs
+++ b/polkadot/runtime/parachains/src/inclusion/tests.rs
@@ -710,6 +710,13 @@ fn bitfield_checks() {
});
}
+#[test]
+fn availability_threshold_is_supermajority() {
+ assert_eq!(3, availability_threshold(4));
+ assert_eq!(5, availability_threshold(6));
+ assert_eq!(7, availability_threshold(9));
+}
+
#[test]
fn supermajority_bitfields_trigger_availability() {
let chain_a = ParaId::from(1_u32);
--
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