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core/state: copy the snap when copying the state #22340

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karalabe merged 2 commits into from
Feb 18, 2021
Merged

core/state: copy the snap when copying the state #22340

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core/state: copy the snap when copying the state
holiman Feb 17, 2021
8226a5c
core/state: deep-copy snap stuff during state Copy
holiman Feb 17, 2021
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25 changes: 25 additions & 0 deletions core/state/statedb.go
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Original file line number Diff line number Diff line change
Expand Up @@ -728,6 +728,31 @@ func (s *StateDB) Copy() *StateDB {
if s.prefetcher != nil {
state.prefetcher = s.prefetcher.copy()
}
if s.snaps != nil {
// In order for the miner to be able to use and make additions
// to the snapshot tree, we need to copy that aswell.
// Otherwise, any block mined by ourselves will cause gaps in the tree,
// and force the miner to operate trie-backed only
state.snaps = s.snaps
state.snap = s.snap
// deep copy needed
state.snapDestructs = make(map[common.Hash]struct{})
for k, v := range s.snapDestructs {
state.snapDestructs[k] = v
}
state.snapAccounts = make(map[common.Hash][]byte)
for k, v := range s.snapAccounts {
state.snapAccounts[k] = v
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@holiman holiman Feb 17, 2021

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Q: do we need to also copy the v byteslice?

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@karalabe karalabe Feb 17, 2021 •
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I don't think so. Important to know though that these values get inserted verbatim into a diff layer and when retrieving storage at least (or account RLP too) those get returned again verbatim. So snapshot.Storage(0x)[2] = 2 would modify it. That said, I don't know of any reason why you'd do such a thing :D

The snapshot explicitly warns:

// Note the returned slot is not a copy, please don't modify it.
func (dl *diffLayer) Storage(accountHash, storageHash common.Hash) ([]byte, error) {

}
state.snapStorage = make(map[common.Hash]map[common.Hash][]byte)
for k, v := range s.snapStorage {
temp := make(map[common.Hash][]byte)
for kk, vv := range v {
temp[kk] = vv
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@holiman holiman Feb 17, 2021

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And here, copy byteslice or not?

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@karalabe karalabe Feb 17, 2021

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Same as account

}
state.snapStorage[k] = temp
}
}
return state
}

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