Formal models and scripts: directio-nrtcaching-dirs

Tools: Python

These are the working models and scripts this part of the hunt used. Some encode the code as it is (a counterexample is the expected result), others a fixed or correct variant; read the header comment of each file. Paths inside them were replaced by placeholders such as $LUCENE (a Lucene checkout) and $WORK.

Findings

• DirectIODirectory accepts a mergeBufferSize that is not a multiple of the file system block size, and then every direct-I/O read fails, so merges hit a tragic exception; a size below the block size can also give a zero-capacity write buffer (BufferOverflowException, or writeBytes making no progress) (finding LFV-226; repro)

Files

• directio-merge-buffer-size-not-block-multiple/model/dio_bmc.py (used for LFV-226)

How to run

• Python: python3 <file>.py; scripts that import z3 need the z3-solver package.

Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.