From 3a56a56d69312a8f97e0b3f150c526f96e844a90 Mon Sep 17 00:00:00 2001
From: "Jeff Washington (jwash)"
 <75863576+jeffwashington@users.noreply.github.com>
Date: Mon, 17 May 2021 18:58:36 -0500
Subject: [PATCH] StoredMetaWriteVersion (#17293)

---
 runtime/src/accounts_db.rs    | 15 ++++++++-------
 runtime/src/append_vec.rs     |  4 +++-
 runtime/src/serde_snapshot.rs |  9 +++++++--
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/runtime/src/accounts_db.rs b/runtime/src/accounts_db.rs
index 0b18684c86..3430776cc7 100644
--- a/runtime/src/accounts_db.rs
+++ b/runtime/src/accounts_db.rs
@@ -25,7 +25,7 @@ use crate::{
         AccountIndexGetResult, AccountSecondaryIndexes, AccountsIndex, AccountsIndexRootsStats,
         Ancestors, IndexKey, IsCached, SlotList, SlotSlice, ZeroLamport,
     },
-    append_vec::{AppendVec, StoredAccountMeta, StoredMeta},
+    append_vec::{AppendVec, StoredAccountMeta, StoredMeta, StoredMetaWriteVersion},
     contains::Contains,
     read_only_accounts_cache::ReadOnlyAccountsCache,
 };
@@ -90,7 +90,7 @@ const CACHE_VIRTUAL_STORAGE_ID: usize = AppendVecId::MAX;
 // for entries in the cache, so that  operations that take a storage entry can maintain
 // a common interface when interacting with cached accounts. This version is "virtual" in
 // that it doesn't actually map to an entry in an AppendVec.
-const CACHE_VIRTUAL_WRITE_VERSION: u64 = 0;
+const CACHE_VIRTUAL_WRITE_VERSION: StoredMetaWriteVersion = 0;
 
 // A specially reserved offset (represents an offset into an AppendVec)
 // for entries in the cache, so that  operations that take a storage entry can maintain
@@ -307,7 +307,7 @@ impl<'a> LoadedAccount<'a> {
         }
     }
 
-    pub fn write_version(&self) -> u64 {
+    pub fn write_version(&self) -> StoredMetaWriteVersion {
         match self {
             LoadedAccount::Stored(stored_account_meta) => stored_account_meta.meta.write_version,
             LoadedAccount::Cached(_) => CACHE_VIRTUAL_WRITE_VERSION,
@@ -3353,9 +3353,9 @@ impl AccountsDb {
         Hash(<[u8; solana_sdk::hash::HASH_BYTES]>::try_from(hasher.finalize().as_slice()).unwrap())
     }
 
-    fn bulk_assign_write_version(&self, count: usize) -> u64 {
+    fn bulk_assign_write_version(&self, count: usize) -> StoredMetaWriteVersion {
         self.write_version
-            .fetch_add(count as u64, Ordering::Relaxed)
+            .fetch_add(count as StoredMetaWriteVersion, Ordering::Relaxed)
     }
 
     fn write_accounts_to_storage<F: FnMut(Slot, usize) -> Arc<AccountStorageEntry>>(
@@ -4818,7 +4818,7 @@ impl AccountsDb {
         accounts: &[(&Pubkey, &impl ReadableAccount)],
         hashes: Option<&[impl Borrow<Hash>]>,
         storage_finder: Option<StorageFinder<'a>>,
-        write_version_producer: Option<Box<dyn Iterator<Item = u64>>>,
+        write_version_producer: Option<Box<dyn Iterator<Item = StoredMetaWriteVersion>>>,
     ) -> StoreAccountsTiming {
         // stores on a frozen slot should not reset
         // the append vec so that hashing could happen on the store
@@ -4956,7 +4956,8 @@ impl AccountsDb {
         // BTreeMap because we want in-order traversal of oldest write_version to newest.
         // Thus, all instances of an account in a store are added to the index in oldest to newest
         // order and we update refcounts and track reclaims correctly.
-        type AccountsMap<'a> = HashMap<Pubkey, BTreeMap<u64, (AppendVecId, StoredAccountMeta<'a>)>>;
+        type AccountsMap<'a> =
+            HashMap<Pubkey, BTreeMap<StoredMetaWriteVersion, (AppendVecId, StoredAccountMeta<'a>)>>;
         let mut slots = self.storage.all_slots();
         #[allow(clippy::stable_sort_primitive)]
         slots.sort();
diff --git a/runtime/src/append_vec.rs b/runtime/src/append_vec.rs
index f0d7a74e35..ae18f94a5e 100644
--- a/runtime/src/append_vec.rs
+++ b/runtime/src/append_vec.rs
@@ -32,13 +32,15 @@ macro_rules! u64_align {
 
 const MAXIMUM_APPEND_VEC_FILE_SIZE: usize = 16 * 1024 * 1024 * 1024; // 16 GiB
 
+pub type StoredMetaWriteVersion = u64;
+
 /// Meta contains enough context to recover the index from storage itself
 /// This struct will be backed by mmaped and snapshotted data files.
 /// So the data layout must be stable and consistent across the entire cluster!
 #[derive(Clone, PartialEq, Debug)]
 pub struct StoredMeta {
     /// global write version
-    pub write_version: u64,
+    pub write_version: StoredMetaWriteVersion,
     /// key for the account
     pub pubkey: Pubkey,
     pub data_len: u64,
diff --git a/runtime/src/serde_snapshot.rs b/runtime/src/serde_snapshot.rs
index 109b3c335b..41044fbb84 100644
--- a/runtime/src/serde_snapshot.rs
+++ b/runtime/src/serde_snapshot.rs
@@ -3,7 +3,7 @@ use {
         accounts::Accounts,
         accounts_db::{AccountStorageEntry, AccountsDb, AppendVecId, BankHashInfo},
         accounts_index::{AccountSecondaryIndexes, Ancestors},
-        append_vec::AppendVec,
+        append_vec::{AppendVec, StoredMetaWriteVersion},
         bank::{Bank, BankFieldsToDeserialize, BankRc, Builtins},
         blockhash_queue::BlockhashQueue,
         epoch_stakes::EpochStakes,
@@ -64,7 +64,12 @@ pub(crate) enum SerdeStyle {
 const MAX_STREAM_SIZE: u64 = 32 * 1024 * 1024 * 1024;
 
 #[derive(Clone, Debug, Default, Deserialize, Serialize, AbiExample)]
-struct AccountsDbFields<T>(HashMap<Slot, Vec<T>>, u64, Slot, BankHashInfo);
+struct AccountsDbFields<T>(
+    HashMap<Slot, Vec<T>>,
+    StoredMetaWriteVersion,
+    Slot,
+    BankHashInfo,
+);
 
 trait TypeContext<'a> {
     type SerializableAccountStorageEntry: Serialize