From af1a52e610324ace9c9cb055b59d00f7ab99fb9c Mon Sep 17 00:00:00 2001
From: jonny rhea <5555162+jrhea@users.noreply.github.com>
Date: Wed, 8 Jul 2026 15:34:48 -0500
Subject: [PATCH] core/rawdb, eth/downloader: fix stale comments about
 re-enabling snap sync on rewind

---
 core/rawdb/accessors_chain.go | 4 ++--
 core/rawdb/schema.go          | 2 +-
 eth/downloader/beaconsync.go  | 4 ++--
 eth/downloader/downloader.go  | 4 ++--
 eth/downloader/syncmode.go    | 8 ++++----
 5 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/core/rawdb/accessors_chain.go b/core/rawdb/accessors_chain.go
index d8825b6b8f..e82a15877e 100644
--- a/core/rawdb/accessors_chain.go
+++ b/core/rawdb/accessors_chain.go
@@ -176,8 +176,8 @@ func WriteFinalizedBlockHash(db ethdb.KeyValueWriter, hash common.Hash) {
 
 // ReadLastPivotNumber retrieves the number of the last pivot block. If the node
 // has never attempted snap sync, the last pivot will always be nil. The marker
-// is written during snap sync and never cleared, so that a rollback past the
-// pivot can re-enable snap sync.
+// is written during snap sync and never cleared, so that a rewind below the
+// pivot can be detected.
 func ReadLastPivotNumber(db ethdb.KeyValueReader) *uint64 {
 	data, _ := db.Get(lastPivotKey)
 	if len(data) == 0 {
diff --git a/core/rawdb/schema.go b/core/rawdb/schema.go
index 54c76143b4..ec72294354 100644
--- a/core/rawdb/schema.go
+++ b/core/rawdb/schema.go
@@ -46,7 +46,7 @@ var (
 	// persistentStateIDKey tracks the id of latest stored state(for path-based only).
 	persistentStateIDKey = []byte("LastStateID")
 
-	// lastPivotKey tracks the last pivot block used by fast sync (to reenable on sethead).
+	// lastPivotKey tracks the last pivot block used by snap sync (to reject sethead below it).
 	lastPivotKey = []byte("LastPivot")
 
 	// fastTrieProgressKey tracks the number of trie entries imported during fast sync.
diff --git a/eth/downloader/beaconsync.go b/eth/downloader/beaconsync.go
index 246fe7637b..2905b664ed 100644
--- a/eth/downloader/beaconsync.go
+++ b/eth/downloader/beaconsync.go
@@ -333,8 +333,8 @@ func (d *Downloader) fetchHeaders(from uint64) error {
 					return errNoPivotHeader
 				}
 				// Write out the pivot into the database so a rollback beyond
-				// it will reenable snap sync and update the state root that
-				// the state syncer will be downloading
+				// it can be detected, and update the state root that the
+				// state syncer will be downloading
 				rawdb.WriteLastPivotNumber(d.stateDB, d.pivotHeader.Number.Uint64())
 			}
 		}
diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 60b04e945b..876115ea97 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -542,8 +542,8 @@ func (d *Downloader) syncToHead() (err error) {
 			if pivotNumber <= origin {
 				origin = pivotNumber - 1
 			}
-			// Write out the pivot into the database so a rollback beyond it will
-			// reenable snap sync
+			// Write out the pivot into the database so a rollback beyond it
+			// can be detected
 			rawdb.WriteLastPivotNumber(d.stateDB, pivotNumber)
 		}
 	}
diff --git a/eth/downloader/syncmode.go b/eth/downloader/syncmode.go
index 036119ce3d..a7792eb5fc 100644
--- a/eth/downloader/syncmode.go
+++ b/eth/downloader/syncmode.go
@@ -40,8 +40,8 @@ func newSyncModer(mode ethconfig.SyncMode, chain BlockChain, disk ethdb.KeyValue
 		// The database seems empty as the current block is the genesis. Yet the snap
 		// block is ahead, so snap sync was enabled for this node at a certain point.
 		// The scenarios where this can happen is
-		// * if the user manually (or via a bad block) rolled back a snap sync node
-		//   below the sync point.
+		// * if an internal reset (a fork config change or corruption recovery)
+		//   rolled a snap sync node back below the sync point.
 		// * the last snap sync is not finished while user specifies a full sync this
 		//   time. But we don't have any recent state for full sync.
 		// In these cases however it's safe to reenable snap sync.
@@ -87,8 +87,8 @@ func (m *syncModer) get(report bool) ethconfig.SyncMode {
 	if report {
 		logger = log.Info
 	}
-	// We are probably in full sync, but we might have rewound to before the
-	// snap sync pivot, check if we should re-enable snap sync.
+	// We are probably in full sync, but an internal reset may have rewound the
+	// chain below the snap sync pivot, check if we should re-enable snap sync.
 	head := m.chain.CurrentBlock()
 	if pivot := rawdb.ReadLastPivotNumber(m.disk); pivot != nil {
 		if head.Number.Uint64() < *pivot {