User design call after watching Pass 2 mark ~20 KB as "Cosmetic"
(permanently Unreadable) after just 10 retries within a single pass:
"i think it's good or maybe until all passes are done. then it's
gone."
That contradicts what the multi-pass design promises a user. The
project goal in CLAUDE.md is "recover 100% of readable data from any
optical disc, automatically." Marking sectors Unreadable after a
SINGLE pass's per-range retry budget gives up on sectors that
subsequent passes might recover — drive reads are stochastic, the
sector that fails 10 times in Pass 2 may succeed on attempt 1 in
Pass 3 after temperature / bus state / prior-read patterns shift.
The patch.rs doc comment already noted ~36% of patch-marked
Unreadable sectors turned out to be readable in re-rip experiments.
Three sites in `Disc::patch` were emitting `PatchItem::Unreadable`
mid-pass:
- backtrack hit damage (line ~2659)
- all-retries-exhausted on a single LBA (line ~2846)
- redundant second mark after the wedge-suspicion log (line ~2970)
All three now emit `PatchItem::NonTrimmed` instead. Failed bytes
stay "maybe" (NonTrimmed) so the next pass gets another shot. The
per-range skip-limit (10) and per-pass wedge-threshold (50) still
bound time-per-pass; they just no longer turn the bytes terminal.
The `PatchItem::Unreadable` variant stays in the enum (with
#[allow(dead_code)]) because the orchestrator-side end-of-recovery
promotion will use it: autorip, after the final retry pass
completes, scans the mapfile and promotes still-NonTrimmed →
Unreadable. That promotion lands in a follow-up commit on the
autorip side — separable from this libfreemkv change.
Loss accounting unchanged: `bytes_pending + bytes_unreadable` is
the "lost or pending" total that `abort_on_lost_secs` consults
(disc/mod.rs:1327). Moving bytes from one bucket to the other
mid-pass doesn't affect whether the rip would abort; it only
affects display (UI shows "Maybe" vs "Cosmetic") and whether
subsequent passes retry the bytes (the actual fix).
Test update: `test_pass_progress_separates_unreadable_from_pending`
was renamed to `test_pass2_leaves_failed_reads_as_pending_not_unreadable`
and rewritten to assert the new invariant — Pass 2 leaves all
failed bytes as bytes_pending (no mid-pass Unreadable promotion).
Original assertions were checking the pre-design-call behavior.
Precommit (cargo +1.86 fmt + clippy + test) green.
Auto-fmt nit on the multi-line map.flush() expression that landed
when the sweep + patch + DiscStream-FrameSource branches were merged
together. No semantic change.
Patch was strictly serial (per-sector recovery: read → seek+write
→ mapfile.record → next). Lifting the write+record onto a consumer
thread lets the drive issue the next per-sector retry while the
previous block's recovered bytes are being committed — small but
real win on damaged discs with many bad sectors, and uniform with
sweep's threading model.
- New PatchSink: Sink<PatchItem> impl in src/disc/patch.rs. Owns
WritebackFile + Mapfile. apply() seeks+writes recovered bytes
and records mapfile state per item; close() runs sync_all and
mapfile.flush.
- Channel depth: WRITE_THROUGH_DEPTH (1). Patch wants minimum
buffering — back-pressure should kick in immediately so the
drive's per-sector retry budget isn't ahead of the writer.
- Disc::patch: keeps every existing recovery decision on the
producer (reverse walk, damage-window skip, NOT_READY pauses,
bridge-degradation handling, wedge exit, range watchdog).
WritebackFile ownership moves to the sink.
Behaviour-preserving: per-sector single-shot read budget unchanged
(BU40N+Initio bridge wedge concern still respected); recovery
algorithm bit-identical.
See freemkv-private/memory/0_18_redesign.md.
Single contributor: MattJackson.
matthew