AccountsHashVerifier remembers last full snapshot info (#30582)

AHV remembers last full snapshot info

core/src/accounts_hash_verifier.rs

@@ -9,10 +9,11 @@ use {
     solana_gossip::cluster_info::{ClusterInfo, MAX_SNAPSHOT_HASHES},
     solana_measure::{measure::Measure, measure_us},
     solana_runtime::{
-        accounts_hash::{AccountsHashEnum, CalcAccountsHashConfig, HashStats},
+        accounts_hash::{AccountsHash, AccountsHashEnum, CalcAccountsHashConfig, HashStats},
         snapshot_config::SnapshotConfig,
         snapshot_package::{
             self, retain_max_n_elements, AccountsPackage, AccountsPackageType, SnapshotPackage,
+            SnapshotType,
         },
         sorted_storages::SortedStorages,
     },
@@ -55,6 +56,7 @@ impl AccountsHashVerifier {
         let t_accounts_hash_verifier = Builder::new()
             .name("solAcctHashVer".to_string())
             .spawn(move || {
+                let mut last_full_snapshot = None;
                 let mut hashes = vec![];
                 loop {
                     if exit.load(Ordering::Relaxed) {
@@ -85,6 +87,7 @@ impl AccountsHashVerifier {
                         &exit,
                         fault_injection_rate_slots,
                         &snapshot_config,
+                        &mut last_full_snapshot,
                     ));
 
                     datapoint_info!(
@@ -184,8 +187,10 @@ impl AccountsHashVerifier {
         exit: &Arc<AtomicBool>,
         fault_injection_rate_slots: u64,
         snapshot_config: &SnapshotConfig,
+        last_full_snapshot: &mut Option<FullSnapshotAccountsHashInfo>,
     ) {
-        let accounts_hash = Self::calculate_and_verify_accounts_hash(&accounts_package);
+        let accounts_hash =
+            Self::calculate_and_verify_accounts_hash(&accounts_package, last_full_snapshot);
 
         Self::save_epoch_accounts_hash(&accounts_package, accounts_hash);
 
@@ -209,7 +214,10 @@ impl AccountsHashVerifier {
     }
 
     /// returns calculated accounts hash
-    fn calculate_and_verify_accounts_hash(accounts_package: &AccountsPackage) -> AccountsHashEnum {
+    fn calculate_and_verify_accounts_hash(
+        accounts_package: &AccountsPackage,
+        last_full_snapshot: &mut Option<FullSnapshotAccountsHashInfo>,
+    ) -> AccountsHashEnum {
         let mut measure_hash = Measure::start("hash");
         let mut sort_time = Measure::start("sort_storages");
         let sorted_storages = SortedStorages::new(&accounts_package.snapshot_storages);
@@ -302,6 +310,17 @@ impl AccountsHashVerifier {
                 None,
             );
         }
+
+        if accounts_package.package_type
+            == AccountsPackageType::Snapshot(SnapshotType::FullSnapshot)
+        {
+            *last_full_snapshot = Some(FullSnapshotAccountsHashInfo {
+                slot: accounts_package.slot,
+                accounts_hash,
+                capitalization: lamports,
+            });
+        }
+
         datapoint_info!(
             "accounts_hash_verifier",
             ("calculate_hash", measure_hash.as_us(), i64),
@@ -450,6 +469,16 @@ impl AccountsHashVerifier {
     }
 }
 
+/// Soon incremental snapshots will no longer calculate a *full* accounts hash.  To support correct
+/// snapshot verification at load time, the incremental snapshot will need to include *this*
+/// information about the full snapshot it was based on.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+struct FullSnapshotAccountsHashInfo {
+    slot: Slot,
+    accounts_hash: AccountsHash,
+    capitalization: u64,
+}
+
 #[cfg(test)]
 mod tests {
     use {
@@ -536,6 +565,7 @@ mod tests {
                 &exit,
                 0,
                 &snapshot_config,
+                &mut None,
             );
 
             // sleep for 1ms to create a newer timestamp for gossip entry