Preserve cache on reverting the snapshot (#2488)

* Preserve cache on reverting the snapshot

* Renamed merge_with into replace_with

* Renamed and documented snapshotting methods
This commit is contained in:
Arkadiy Paronyan 2016-10-06 15:54:05 +02:00 committed by Gav Wood
parent e380955c34
commit 6c1b2fbed5
4 changed files with 63 additions and 22 deletions

View File

@ -265,7 +265,7 @@ impl<'a> Executive<'a> {
let cost = self.engine.cost_of_builtin(&params.code_address, data);
if cost <= params.gas {
self.engine.execute_builtin(&params.code_address, data, &mut output);
self.state.clear_snapshot();
self.state.discard_snapshot();
// trace only top level calls to builtins to avoid DDoS attacks
if self.depth == 0 {
@ -285,7 +285,7 @@ impl<'a> Executive<'a> {
Ok(params.gas - cost)
} else {
// just drain the whole gas
self.state.revert_snapshot();
self.state.revert_to_snapshot();
tracer.trace_failed_call(trace_info, vec![], evm::Error::OutOfGas.into());
@ -331,7 +331,7 @@ impl<'a> Executive<'a> {
res
} else {
// otherwise it's just a basic transaction, only do tracing, if necessary.
self.state.clear_snapshot();
self.state.discard_snapshot();
tracer.trace_call(trace_info, U256::zero(), trace_output, vec![]);
Ok(params.gas)
@ -473,10 +473,10 @@ impl<'a> Executive<'a> {
| Err(evm::Error::BadInstruction {.. })
| Err(evm::Error::StackUnderflow {..})
| Err(evm::Error::OutOfStack {..}) => {
self.state.revert_snapshot();
self.state.revert_to_snapshot();
},
Ok(_) | Err(evm::Error::Internal) => {
self.state.clear_snapshot();
self.state.discard_snapshot();
substate.accrue(un_substate);
}
}

View File

@ -394,7 +394,7 @@ impl Account {
/// Replace self with the data from other account merging storage cache.
/// Basic account data and all modifications are overwritten
/// with new values.
pub fn merge_with(&mut self, other: Account) {
pub fn overwrite_with(&mut self, other: Account) {
self.balance = other.balance;
self.nonce = other.nonce;
self.storage_root = other.storage_root;

View File

@ -93,7 +93,7 @@ impl AccountEntry {
}
}
// Create a new account entry and mark it as dirty
// Create a new account entry and mark it as dirty.
fn new_dirty(account: Option<Account>) -> AccountEntry {
AccountEntry {
account: account,
@ -101,13 +101,27 @@ impl AccountEntry {
}
}
// Create a new account entry and mark it as clean
// Create a new account entry and mark it as clean.
fn new_clean(account: Option<Account>) -> AccountEntry {
AccountEntry {
account: account,
state: AccountState::Clean,
}
}
// Replace data with another entry but preserve storage cache.
fn overwrite_with(&mut self, other: AccountEntry) {
self.state = other.state;
match other.account {
Some(acc) => match self.account {
Some(ref mut ours) => {
ours.overwrite_with(acc);
},
None => {},
},
None => self.account = None,
}
}
}
/// Representation of the entire state of all accounts in the system.
@ -142,10 +156,24 @@ impl AccountEntry {
///
/// Upon destruction all the local cache data merged into the global cache.
/// The merge might be rejected if current state is non-canonical.
///
/// State snapshotting.
///
/// A new snapshot can be created with `snapshot()`. Snapshots can be
/// created in a hierarchy.
/// When a snapshot is active all changes are applied directly into
/// `cache` and the original value is copied into an active snapshot.
/// Reverting a snapshot with `revert_to_snapshot` involves copying
/// original values from the latest snapshot back into `cache`. The code
/// takes care not to overwrite cached storage while doing that.
/// Snapshot can be discateded with `discard_snapshot`. All of the orignal
/// backed-up values are moved into a parent snapshot (if any).
///
pub struct State {
db: StateDB,
root: H256,
cache: RefCell<HashMap<Address, AccountEntry>>,
// The original account is preserved in
snapshots: RefCell<Vec<HashMap<Address, Option<AccountEntry>>>>,
account_start_nonce: U256,
factories: Factories,
@ -199,31 +227,44 @@ impl State {
Ok(state)
}
/// Create a recoverable snaphot of this state
/// Create a recoverable snaphot of this state.
pub fn snapshot(&mut self) {
self.snapshots.borrow_mut().push(HashMap::new());
}
/// Merge last snapshot with previous
pub fn clear_snapshot(&mut self) {
/// Merge last snapshot with previous.
pub fn discard_snapshot(&mut self) {
// merge with previous snapshot
let last = self.snapshots.borrow_mut().pop();
if let Some(mut snapshot) = last {
if let Some(ref mut prev) = self.snapshots.borrow_mut().last_mut() {
if prev.is_empty() {
**prev = snapshot;
} else {
for (k, v) in snapshot.drain() {
prev.entry(k).or_insert(v);
}
}
}
}
}
/// Revert to snapshot
pub fn revert_snapshot(&mut self) {
/// Revert to the last snapshot and discard it.
pub fn revert_to_snapshot(&mut self) {
if let Some(mut snapshot) = self.snapshots.borrow_mut().pop() {
for (k, v) in snapshot.drain() {
match v {
Some(v) => {
self.cache.borrow_mut().insert(k, v);
match self.cache.borrow_mut().entry(k) {
Entry::Occupied(mut e) => {
// Merge snapshotted changes back into the main account
// storage preserving the cache.
e.get_mut().overwrite_with(v);
},
Entry::Vacant(e) => {
e.insert(v);
}
}
},
None => {
match self.cache.borrow_mut().entry(k) {
@ -1717,12 +1758,12 @@ fn snapshot_basic() {
state.snapshot();
state.add_balance(&a, &U256::from(69u64));
assert_eq!(state.balance(&a), U256::from(69u64));
state.clear_snapshot();
state.discard_snapshot();
assert_eq!(state.balance(&a), U256::from(69u64));
state.snapshot();
state.add_balance(&a, &U256::from(1u64));
assert_eq!(state.balance(&a), U256::from(70u64));
state.revert_snapshot();
state.revert_to_snapshot();
assert_eq!(state.balance(&a), U256::from(69u64));
}
@ -1735,9 +1776,9 @@ fn snapshot_nested() {
state.snapshot();
state.add_balance(&a, &U256::from(69u64));
assert_eq!(state.balance(&a), U256::from(69u64));
state.clear_snapshot();
state.discard_snapshot();
assert_eq!(state.balance(&a), U256::from(69u64));
state.revert_snapshot();
state.revert_to_snapshot();
assert_eq!(state.balance(&a), U256::from(0));
}

View File

@ -191,7 +191,7 @@ impl StateDB {
for (address, account) in self.cache_overlay.drain(..) {
if let Some(&mut Some(ref mut existing)) = cache.accounts.get_mut(&address) {
if let Some(new) = account {
existing.merge_with(new);
existing.overwrite_with(new);
continue;
}
}