core: fix setHead cornercase where the threshold root has state

core/blockchain.go

@@ -360,19 +360,18 @@ func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, chainConfig *par
 	}
 	// Load any existing snapshot, regenerating it if loading failed
 	if bc.cacheConfig.SnapshotLimit > 0 {
-		var (
-			recovery bool
-			flag     = rawdb.ReadSnapshotRecoveryNumber(bc.db)
-		)
-		// The persisted snapshot recovery height is higher than
-		// current chain head. At least it means the snapshot disk
-		// layer is higher than current head. Enable the snapshot
-		// recovery mode.
-		if flag != nil && *flag > bc.CurrentBlock().NumberU64() {
-			recovery = true
-			log.Info("Enable snapshot recovery", "chainhead", bc.CurrentBlock().NumberU64(), "disklayer", *flag)
+		// If the chain was rewound past the snapshot persistent layer (causing
+		// a recovery block number to be persisted to disk), check if we're still
+		// in recovery mode and in that case, don't invalidate the snapshot on a
+		// head mismatch.
+		var recover bool
+
+		head := bc.CurrentBlock()
+		if layer := rawdb.ReadSnapshotRecoveryNumber(bc.db); layer != nil && *layer > head.NumberU64() {
+			log.Warn("Enabling snapshot recovery", "chainhead", head.NumberU64(), "diskbase", *layer)
+			recover = true
 		}
-		bc.snaps = snapshot.New(bc.db, bc.stateCache.TrieDB(), bc.cacheConfig.SnapshotLimit, bc.CurrentBlock().Root(), !bc.cacheConfig.SnapshotWait, recovery)
+		bc.snaps = snapshot.New(bc.db, bc.stateCache.TrieDB(), bc.cacheConfig.SnapshotLimit, head.Root(), !bc.cacheConfig.SnapshotWait, recover)
 	}
 	// Take ownership of this particular state
 	go bc.update()
@@ -517,11 +516,11 @@ func (bc *BlockChain) SetHeadBeyondRoot(head uint64, root common.Hash) (uint64,
 				beyondRoot := (root == common.Hash{}) // Flag whether we're beyond the requested root (no root, always true)
 
 				for {
+					// If a root threshold was requested but not yet crossed, check
+					if root != (common.Hash{}) && !beyondRoot && newHeadBlock.Root() == root {
+						beyondRoot, rootNumber = true, newHeadBlock.NumberU64()
+					}
 					if _, err := state.New(newHeadBlock.Root(), bc.stateCache, bc.snaps); err != nil {
-						// If a root threshold was requested but not yet crossed, check
-						if root != (common.Hash{}) && !beyondRoot && newHeadBlock.Root() == root {
-							beyondRoot, rootNumber = true, newHeadBlock.NumberU64()
-						}
 						log.Trace("Block state missing, rewinding further", "number", newHeadBlock.NumberU64(), "hash", newHeadBlock.Hash())
 						if pivot == nil || newHeadBlock.NumberU64() > *pivot {
 							newHeadBlock = bc.GetBlock(newHeadBlock.ParentHash(), newHeadBlock.NumberU64()-1)
@@ -535,7 +534,7 @@ func (bc *BlockChain) SetHeadBeyondRoot(head uint64, root common.Hash) (uint64,
 						log.Debug("Rewound to block with state", "number", newHeadBlock.NumberU64(), "hash", newHeadBlock.Hash())
 						break
 					}
-					log.Debug("Skip the block with state", "number", newHeadBlock.NumberU64(), "hash", newHeadBlock.Hash())
+					log.Debug("Skipping block with thershold state", "number", newHeadBlock.NumberU64(), "hash", newHeadBlock.Hash(), "root", newHeadBlock.Root())
 					newHeadBlock = bc.GetBlock(newHeadBlock.ParentHash(), newHeadBlock.NumberU64()-1) // Keep rewinding
 				}
 			}