We saw a case where the recovery stats reported `recovered_bytes` greater than `length_in_bytes` for one file:

```
GET /_recovery?detailed

200 OK
...
{
  "name": "_buk.fdt",
  "length_in_bytes": 26891307173,
  "reused": false,
  "recovered_in_bytes": 35324928266,
  "recovered_from_snapshot_in_bytes": 8433621093
}
...
```

NB `35324928266 == 26891307173 + 8433621093`

This causes Elasticsearch to compute a negative value for the reserved space on the target node of this recovery, which prevents stats APIs from working. This appears to be caused by a network-level failure which triggers a retry without first cancelling an ongoing download of a different file with the same name from the snapshot repository.

---

### Workaround

Restart the target node to clear these stats.
x-pack/plugin/searchable-snapshots/src/main/java/org/elasticsearch/xpack/searchablesnapshots/recovery/SearchableSnapshotRecoveryState.java
if (getStage() == Stage.FINALIZE) {
            super.setStage(Stage.DONE);
        }
        SearchableSnapshotRecoveryState.Index index = (Index) getIndex();
        index.stopTimer();
        preWarmComplete = true;
    }
    public synchronized boolean isPreWarmComplete() {
        return preWarmComplete;
    }
    public synchronized void ignoreFile(String name) {
        SearchableSnapshotRecoveryState.Index index = (Index) getIndex();
        index.addFileToIgnore(name);
    }
    public synchronized void markIndexFileAsReused(String name) {
        SearchableSnapshotRecoveryState.Index index = (Index) getIndex();
        index.markFileAsReused(name);
    }
    private static final class Index extends RecoveryState.Index {
        
        
        
        
        private final Set<String> filesToIgnore = new HashSet<>();
        private Index() {
            super(new SearchableSnapshotRecoveryFilesDetails());