core, eth: abort snapshot generation on snap sync and resume later

core/rawdb/accessors_snapshot.go

@@ -24,6 +24,26 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 )
 
+// ReadSnapshotDisabled retrieves if the snapshot maintenance is disabled.
+func ReadSnapshotDisabled(db ethdb.KeyValueReader) bool {
+	disabled, _ := db.Has(snapshotDisabledKey)
+	return disabled
+}
+
+// WriteSnapshotDisabled stores the snapshot pause flag.
+func WriteSnapshotDisabled(db ethdb.KeyValueWriter) {
+	if err := db.Put(snapshotDisabledKey, []byte("42")); err != nil {
+		log.Crit("Failed to store snapshot disabled flag", "err", err)
+	}
+}
+
+// DeleteSnapshotDisabled deletes the flag keeping the snapshot maintenance disabled.
+func DeleteSnapshotDisabled(db ethdb.KeyValueWriter) {
+	if err := db.Delete(snapshotDisabledKey); err != nil {
+		log.Crit("Failed to remove snapshot disabled flag", "err", err)
+	}
+}
+
 // ReadSnapshotRoot retrieves the root of the block whose state is contained in
 // the persisted snapshot.
 func ReadSnapshotRoot(db ethdb.KeyValueReader) common.Hash {