fix: reject Floor in pinned mode instead of leaking GC-pool segments

[thweetkomputer]

Problem

A FloorRequest resolves a large-value floor entry into its own IoStringBuffer (floor_req->large_value_). In KV Cache pinned mode, GetGlobalRegisteredMemory() returns the shard-private GC pool, whose segments no public API can Recycle. So every Floor that lands on a large-value entry permanently drains num_segments from that pool. Once it empties, background segment compaction spins on YieldToLowPQ forever (space reclamation halts) and later large-value Floors hang.

Read already rejects its IoStringBuffer overload in pinned mode for exactly this reason (pinned callers must use the pinned-destination overloads). Floor has no pinned-destination variant, and its dispatch was missing the equivalent guard.

Fix

Reject FloorRequest in pinned mode (pinned_memory_chunks non-empty) with InvalidArgs, mirroring the Read guard.

Test

large_value_e2e [pinned]: a Floor against a pinned-mode store now returns InvalidArgs; without the guard it returns NoError (leaking the segments). Full suite passes (448 assertions).

Summary by CodeRabbit

• Bug Fixes

  • Invalid Floor requests involving large values in pinned-memory mode are now rejected with a clear InvalidArgs error instead of being processed unsuccessfully.

• Tests

  • Added coverage verifying that pinned large-value Floor requests are rejected as expected.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ee7a5970-b43b-4187-aaf6-4b81ba24aa62

📥 Commits

Reviewing files that changed from the base of the PR and between 51dc37d and ebd356d.

📒 Files selected for processing (2)

• src/storage/shard.cpp
• tests/large_value_e2e.cpp

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Walkthrough

Floor requests now return InvalidArgs when pinned-memory chunks are enabled. A pinned-mode end-to-end test verifies this behavior after writing a large value.

Changes

Pinned-mode Floor rejection

Layer / File(s)	Summary
Floor guard and end-to-end validation src/storage/shard.cpp, tests/large_value_e2e.cpp	Shard::ProcessReq rejects pinned-mode Floor requests with InvalidArgs; the new test verifies rejection for a pinned large value and performs cleanup.

Estimated code review effort: 2 (Simple) | ~10 minutes

Poem

I’m a rabbit guarding the shard,
Pinned floors now fail before they start.
A large value hops into place,
Then InvalidArgs wins the race.
Tests tidy the burrow with grace.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and accurately summarizes the main change: rejecting Floor in pinned mode to avoid GC-pool leaks.
Description check	✅ Passed	The description covers the problem, fix, and test, but it omits the issue reference requested by the template.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/floor-pinned-mode-guard

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