SDSTOR-20656: clear wbc chunk selector

[nnastonen]

0. Create homestore with chunk selector
1. Create btree1 and populate it
2. Nodes get into wbc cache
3. Destroy btree1 (wbc purge is not done, also volume's chunk bitmap is not cleared)
4. Create btree2 and populate it
5. Nodes get into wbc cache and we get cache corruption, duplicate inserts

This change makes chunk release asynchronous and defers returning the chunk to the free pool until cleanup is complete.

New flow:

• detach the volume's chunk list from m_volume_chunks
• run asynchronous cleanup for all the chunks
• in cleanup, evict all allocated blkids for the chunks from WBC
• [reset the chunks' block allocator state (bitmap)]
• reinsert the chunks into m_per_dev_chunks

This PR also addresses this ticket SDSTOR-25404

[JacksonYao287]

why we need this _PRERELEASE here? I think target_compile_definitions(test_index_chunk_selector PRIVATE _PRERELEASE) in tests/CmakeLists.txt is enough for the new test case

[nnastonen]

Because otherwise the code won't compile.

[JacksonYao287]

adding _PRERELEASE unconditionally to the homestore library itself means every build (including production Release builds) will now permanently carry _PRERELEASE: extra fault-injection checkpoints, extra assert branches, and extra debug fields get baked into the production library. That's a much bigger behavioral change than "just make the new test compile." pls correct me if I misunderstand something.

[nnastonen]

You are right. I added _PRERELEASE just to make this compile and run. Please suggest a better place/way to enable _PRERELEASE as I didn't really find how it is enabled in 7.x. I presume it is not the same as Debug build.

[JacksonYao287]

@szmyd since we disable prerelease in eBay/sisl#278, do you have any sugestion on this ?

[xiaoxichen]

@szmyd @shosseinimotlagh Please if you can ensure the upgrade path and compatibility are properly discussed.

NuObject is moving to V7 mostly to intake the folly and co-routine removal, which is still a persistent-compatible version (meaning , no data migration is needed upgrading from v6 to v7).

With the potential path forward of this feature, it is unlikely to be compatible with v7 as of now. I would suggest it should be in V8 with proper feature bit. Also decisions regarding how V6 can upgrade to V8 should be discussed.

[szmyd]

Also decisions regarding how V6 can upgrade to V8 should be discussed.

It's my understanding that we only use v3 (NuBlox 1.x/2.0) and v7 (NuObject) at the moment. We're currently working on v8 for NuBlox 2.1; so where does v6 come into play?

[xiaoxichen]

@szmyd sorry you are right, I mess up v7 vs v6.. Yes I am talking about v7 ->v8 compatibility

[Copilot]

🟡 Changes recommended

Production cleanup is not wired into chunk release, and the build and test lifecycle contain blocking defects.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Introduces chunk-level WBC eviction primitives intended to prevent stale cache entries when index chunks are reused.

Changes:

• Adds allocated-block enumeration and WBC chunk eviction APIs.
• Adds a deterministic chunk-reuse regression test.
• Updates test helpers, build configuration, and package version.

File summaries

File	Description
conanfile.py	Bumps version to 8.2.1.
src/CMakeLists.txt	Enables prerelease compilation.
src/include/homestore/index/wb_cache_base.hpp	Exposes chunk eviction API.
src/lib/device/chunk.cpp	Enumerates allocated blocks.
src/lib/device/chunk.h	Declares block enumeration.
src/lib/index/wb_cache.cpp	Implements chunk-wide eviction.
src/lib/index/wb_cache.hpp	Declares eviction override.
src/tests/CMakeLists.txt	Registers the regression test.
src/tests/btree_helpers/btree_test_helper.hpp	Makes flip arguments explicit arrays.
src/tests/test_common/homestore_test_common.hpp	Makes flip arguments explicit arrays.
src/tests/test_index_chunk_selector.cpp	Adds the chunk-reuse regression test.

Review details

• Files reviewed: 11/11 changed files
• Comments generated: 4
• Review effort level: Balanced

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[JacksonYao287]

thanks @nnastonen for this change, I have no more in put. @szmyd @shosseinimotlagh can you give some inputs?

[JacksonYao287]

@szmyd since we disable prerelease in eBay/sisl#278, do you have any sugestion on this ?

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 18.75000% with 13 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (dev/v8.x@d1f8ea2). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/lib/device/chunk.cpp	0.00%	8 Missing ⚠️
src/lib/index/wb_cache.cpp	37.50%	5 Missing ⚠️
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Additional details and impacted files

@@             Coverage Diff             @@
##             dev/v8.x     #912   +/-   ##
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  Coverage            ?   46.02%           
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  Files               ?      111           
  Lines               ?    12485           
  Branches            ?     5882           
===========================================
  Hits                ?     5746           
  Misses              ?     3195           
  Partials            ?     3544           

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