Motivation

WT-18465 fixed the observed deadlock by marking the shared history store last, but the root invariant remains: a thread holding eviction state must not block on the handle-list or schema locks while opening the history store. This has recurred through WT-5785/WT-5946, WT-7053, WT-14957, and WT-18465.

Make reconciliation under WT_REC_EVICT use only a cached HS cursor. On a miss, fail the eviction attempt with EBUSY, leave the page resident for retry, and increment a dedicated statistic. The failure mode should be a skipped eviction, not a hung step-down or an annual rare deadlock. Checkpoint reconciliation should retain the normal HS open because it does not hold eviction state.

Implementation constraints from WT-18465 review

This must not be implemented by returning EBUSY directly from _wti_rec_hs_insert_updates. That function runs inside _rec_write_wrapup, where errors currently panic rather than propagate as recoverable eviction failures.

At minimum:

• Preflight all required cached HS cursors before entering reconciliation wrapup.
• Route a miss through the complete pre-wrapup cleanup path.
• Cover every HS open used by eviction reconciliation, not only update insertion.
• Handle paths that need two HS cursors simultaneously.
• Preserve behavior when cache_cursors=false, where cursor-cache-only lookup can never succeed.
• Avoid using WT_REC_EVICT alone as proof that the caller can retry; whole-file close also sets it.
• Keep the miss statistic meaningful in production.

Acceptance criteria

• No eviction reconciliation path takes the handle-list or schema lock while holding evict_busy.
• A missing cached HS cursor returns EBUSY through normal eviction handling without panic.
• Existing tests pass with cursor caching enabled and disabled.
• A regression test demonstrates that a forced cache miss produces a retryable eviction failure and records the statistic.

References

• WT-18465
• WT-14957
• WT-7053
• WT-5785
• WT-5946