Complements the wedge-skip backstop (d7f1862) with proactive
avoidance so we don't HIT the wedge in the first place. User's
take after seeing the Dune Pt 2 rip wedge at 48%: 'we shouldn't be
wedging.'
Empirical observations from the 23:09:12-23:09:55 wedge timeline:
5 read errors over 43 s, ~8 s apart (drive's own ECC recovery
takes 5-10 s per failure). Not 'hammering' in any usual sense,
but cumulative firmware-state buildup over 5 in-cluster errors
was enough to tip the BU40N into wedge mode at the 5th error.
Damage cluster spanned ~140 MB (LBAs 19.898M-19.965M). Current
damage-jump base of 256 sectors × batch=32 = 16 MB first jump,
doubling to 32 MB, 64 MB... Each jump landed BACK INSIDE the
140 MB cluster, exposing the drive to MORE in-cluster errors.
Two avoidance levers:
1. Inter-error pause on Pass 1 (PASS_1_FAIL_PAUSE_SECS = 5 s):
pre-fix Pass 1 ran pause_secs=0 on all errors to 'zoom past'
damage zones. Successful reads still zoom at zero pause — the
pause applies only to FAILED reads, giving the drive's firmware
cool-down between cluster exposures. Cost: ~5 s per scattered
failure (~30-60 s total on a damage cluster); trivial vs.
crashing the rip at 48%.
2. Larger damage-jump base (JUMP_BASE_SECTORS = 1024, up from
256): first jump at batch=32 now covers 64 MB instead of 16 MB,
second jump 128 MB instead of 32 MB. Two jumps clear 192 MB —
well past most single-cluster damage patterns. Smaller jumps
were landing inside the cluster and adding to the wedge counter.
Plus a halt-aware sleep helper (sleep_secs_or_halt) so the new
inter-error pause doesn't degrade halt response time. Halt poll
granularity 100 ms — halt fires within ~100 ms regardless of
remaining pause time. Updated three sleep call sites in disc/mod.rs
(SkipBlock pause, JumpAhead post-pause, Retry pause).
The wedge-SKIP backstop (d7f1862) stays — combined with this
avoidance work, the flow becomes:
damage cluster encountered →
pause 5 s, mark NonTrimmed →
second failure →
pause 5 s, mark NonTrimmed →
...
threshold hit →
damage-jump 64 MB (clears 95% of clusters) →
if jump lands in another cluster: 128 MB next jump →
only if drive STILL wedges after all this:
wedge-skip kicks in (1 GB jump + 30 s cooldown × 16 budget)
Tests:
pass_1_pauses_briefly_on_skip_for_wedge_avoidance — locks the
new 5 s pause behavior in place (replaces the old pause=0 test).
integration test threshold bumped from 5 s to 60 s with comment
explaining the new bound is 'not infinite' rather than
'milliseconds-fast'.
All 433+ tests green on cargo +1.86 fmt + clippy + test.
Precommit green.
matthew
445a15fa25