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.
server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
assert recoveryState.getRecoverySource().equals(shardRouting.recoverySource());
        switch (recoveryState.getRecoverySource().getType()) {
            case EMPTY_STORE:
            case EXISTING_STORE:
                executeRecovery("from store", recoveryState, recoveryListener, this::recoverFromStore);
                break;
            case PEER:
                try {
                    markAsRecovering("from " + recoveryState.getSourceNode(), recoveryState);
                    recoveryTargetService.startRecovery(this, recoveryState.getSourceNode(), recoveryListener);
                } catch (Exception e) {
                    failShard("corrupted preexisting index", e);
                    recoveryListener.onRecoveryFailure(recoveryState, new RecoveryFailedException(recoveryState, null, e), true);
                }