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v0.13.22 — replace bisect-on-fail with hysteresis Block↔Single

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The v0.13.21 bisect-on-fail recovery was correct (100% of recoverable
sectors picked up) but slow on dense damage clusters. Live test on
Dune 2 v0.13.21 burned ~30 s per damaged 60-block — paying a ~5 s
kernel ABORT/timeout at every level of a log₂(60) ≈ 6 deep DFS, on
the failing branch each time.

Replaced with a two-state hysteresis machine in Disc::copy:

  Block(batch):
    read(batch) ok    → write, advance, stay Block
    read(batch) fail  → switch to Single, retry SAME range at bpt=1

  Single:
    read(1) ok    → write, consecutive_good++
                    if consecutive_good >= BPT1_EXIT_THRESHOLD:
                      switch to Block, reset counter
    read(1) fail  → mark NonTrimmed, consecutive_good = 0

BPT1_EXIT_THRESHOLD = 10_000 sectors (= 20 MB clean run). Calibrated
from the 2026-04-26 BU40N empirical probe data; tunable.

Per-block math on a damaged 60-block with 1 truly bad sector:

  Bisect      (v0.13.21): ~30 s  (5 s × 6 levels)
  Hysteresis  (v0.13.22): ~10 s  (5 s bpt=batch fail
                                  + 59 × 1 ms good
                                  + 1 × 5 s bad)

Inside a damaged cluster spanning many 60-blocks the win compounds:
hysteresis pays the bpt=batch fail cost ONCE on entry, then stays at
bpt=1 across the cluster; bisection re-paid it every 60 sectors. For
Dune 2's ~1248-sector boundary cluster that's ~21 fewer 5-sec
kernel timeouts ≈ 100 s saved per pass.

Telemetry: new phase=mode_change trace event with from, to, lba, and
consecutive_good. Replaces v0.13.21's phase=bisect. Worklist DFS is
gone — single iterative for s in 0..count on the failure path.

Test rename, same fixture and same 100% recovery expectation:
  test_disc_copy_bisect_recovers_via_single_sector_reads
  → test_disc_copy_hysteresis_recovers_via_single_sector_reads

Also adds DamageSeverity (Clean / Cosmetic / Moderate / Serious) +
classify_damage(bad_sectors, lost_ms), re-exported from libfreemkv,
so applications can render structured severity instead of formatting
their own from raw counters.
This commit is contained in:
matthew
2026-04-26 17:27:57 -07:00
parent 4eca4104ce
commit 0ecf7c7c46
5 changed files with 301 additions and 83 deletions
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src/lib.rs
+4 -3
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@@ -134,9 +134,10 @@ pub use decrypt::{DecryptKeys, decrypt_sectors};
// background. The codec / channel / resolution enums are the canonical
// structured representation; never compare against display strings.
pub use disc::{
AacsState, AudioChannels, AudioStream, Clip, Codec, ColorSpace, ContentFormat, Disc,
DiscFormat, DiscId, DiscTitle, Extent, FrameRate, HdrFormat, KeySource, LabelPurpose,
LabelQualifier, Resolution, SampleRate, ScanOptions, Stream, SubtitleStream, VideoStream,
AacsState, AudioChannels, AudioStream, Clip, Codec, ColorSpace, ContentFormat,
DamageSeverity, Disc, DiscFormat, DiscId, DiscTitle, Extent, FrameRate, HdrFormat,
KeySource, LabelPurpose, LabelQualifier, Resolution, SampleRate, ScanOptions, Stream,
SubtitleStream, VideoStream, classify_damage,
};
// ─── Streams ────────────────────────────────────────────────────────────────