keep track of oldest slot used by last hash calculation (#25152)

core/src/accounts_hash_verifier.rs

@@ -147,6 +147,14 @@ impl AccountsHashVerifier {
             )
             .unwrap();
 
+        accounts_package
+            .accounts
+            .accounts_db
+            .notify_accounts_hash_calculated_complete(
+                sorted_storages.max_slot_inclusive(),
+                &accounts_package.epoch_schedule,
+            );
+
         assert_eq!(accounts_package.expected_capitalization, lamports);
         if let Some(expected_hash) = accounts_package.accounts_hash_for_testing {
             assert_eq!(expected_hash, accounts_hash);

runtime/src/accounts_db.rs

@@ -999,6 +999,9 @@ pub struct AccountsDb {
     /// Keeps tracks of index into AppendVec on a per slot basis
     pub accounts_index: AccountInfoAccountsIndex,
 
+    /// slot that is one epoch older than the highest slot where accounts hash calculation has completed
+    pub accounts_hash_complete_one_epoch_old: RwLock<Slot>,
+
     /// true iff rent exempt accounts are not rewritten in their normal rent collection slot
     pub skip_rewrites: bool,
 
@@ -1611,6 +1614,7 @@ impl AccountsDb {
 
         AccountsDb {
             active_stats: ActiveStats::default(),
+            accounts_hash_complete_one_epoch_old: RwLock::default(),
             skip_rewrites: false,
             ancient_append_vecs: false,
             accounts_index,
@@ -2000,6 +2004,22 @@ impl AccountsDb {
         }
     }
 
+    /// hash calc is completed as of 'slot'
+    /// so, any process that wants to take action on really old slots can now proceed up to 'slot'-slots per epoch
+    pub fn notify_accounts_hash_calculated_complete(
+        &self,
+        completed_slot: Slot,
+        epoch_schedule: &EpochSchedule,
+    ) {
+        let one_epoch_old_slot = completed_slot.saturating_sub(
+            epoch_schedule.get_slots_in_epoch(epoch_schedule.get_epoch(completed_slot)),
+        );
+        let mut accounts_hash_complete_one_epoch_old =
+            self.accounts_hash_complete_one_epoch_old.write().unwrap();
+        *accounts_hash_complete_one_epoch_old =
+            std::cmp::max(*accounts_hash_complete_one_epoch_old, one_epoch_old_slot);
+    }
+
     /// Collect all the uncleaned slots, up to a max slot
     ///
     /// Search through the uncleaned Pubkeys and return all the slots, up to a maximum slot.