Migration for over locked accounts in phgragmen elections (paritytech…

…#10649)

* use free balance rather than total balance

* Docs

* Migration for over-locked phrag voters

* New line

* comment

* Update frame/elections-phragmen/src/migrations/v5.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Only set lock, don't remove it

* delete commented out

* docs

* Update migration to just take a set of accounts

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

frame/elections-phragmen/src/migrations/mod.rs

@@ -21,3 +21,5 @@
 pub mod v3;
 /// Version 4.
 pub mod v4;
+/// Version 5.
+pub mod v5;

frame/elections-phragmen/src/migrations/v5.rs

@@ -0,0 +1,70 @@
+use super::super::*;
+
+/// Migrate the locks and vote stake on accounts (as specified with param `to_migrate`) that have
+/// more than their free balance locked.
+///
+/// This migration addresses a bug were a voter could lock up to their reserved balance + free
+/// balance. Since locks are only designed to operate on free balance, this put those affected in a
+/// situation where they could increase their free balance but still not be able to use their funds
+/// because they were less than the lock.
+pub fn migrate<T: Config>(to_migrate: Vec<T::AccountId>) -> Weight {
+ let mut weight = 0;
+
+ for who in to_migrate.iter() {
+ if let Ok(mut voter) = Voting::<T>::try_get(who) {
+ let free_balance = T::Currency::free_balance(&who);
+
+ weight = weight.saturating_add(T::DbWeight::get().reads(2));
+
+ if voter.stake > free_balance {
+ voter.stake = free_balance;
+ Voting::<T>::insert(&who, voter);
+
+ let pallet_id = T::PalletId::get();
+ T::Currency::set_lock(pallet_id, &who, free_balance, WithdrawReasons::all());
+
+ weight = weight.saturating_add(T::DbWeight::get().writes(2));
+ }
+ }
+ }
+
+ weight
+}
+
+/// Given the list of voters to migrate return a function that does some checks and information
+/// prior to migration. This can be linked to [`frame_support::traits::OnRuntimeUpgrade::
+/// pre_upgrade`] for further testing.
+pub fn pre_migrate_fn<T: Config>(to_migrate: Vec<T::AccountId>) -> Box<dyn Fn() -> ()> {
+ Box::new(move || {
+ for who in to_migrate.iter() {
+ if let Ok(voter) = Voting::<T>::try_get(who) {
+ let free_balance = T::Currency::free_balance(&who);
+
+ if voter.stake > free_balance {
+ // all good
+ } else {
+ log::warn!("pre-migrate elections-phragmen: voter={:?} has less stake then free balance", who);
+ }
+ } else {
+ log::warn!("pre-migrate elections-phragmen: cannot find voter={:?}", who);
+ }
+ }
+ log::info!("pre-migrate elections-phragmen complete");
+ })
+}
+
+/// Some checks for after migration. This can be linked to
+/// [`frame_support::traits::OnRuntimeUpgrade::post_upgrade`] for further testing.
+///
+/// Panics if anything goes wrong.
+pub fn post_migrate<T: crate::Config>() {
+ for (who, voter) in Voting::<T>::iter() {
+ let free_balance = T::Currency::free_balance(&who);
+
+ assert!(voter.stake <= free_balance, "migration should have made locked <= free_balance");
+ // Ideally we would also check that the locks and AccountData.misc_frozen where correctly
+ // updated, but since both of those are generic we can't do that without further bounding T.
+ }
+
+ log::info!("post-migrate elections-phragmen complete");
+}