[nnastonen]

When a chunk is reset (for example when HomeBlocks releases a destroyed volume's chunks), reset_block_allocator() deletes the chunk's bitmap meta blk and replaces the allocator with a new one. A CP flush running at the same time can still hold the old allocator and flush it afterwards. Depending on timing, one of two things happens:

1. The old bitmap is written back. The flush saves the pre-reset bitmap as a new meta blk. After a crash, the reset chunk comes back with blocks still marked allocated, and that extra meta blk is never cleaned up.
2. Crash. The flush updates the meta blk that the reset just deleted, with a null or freed cookie. _PRERELEASE builds assert ("null cookie!"); release builds hit a null dereference or a use-after-free.

Fix
Make BitmapBlkAllocator::reset() and cp_flush() mutually exclusive, and stop flushing an allocator once it has been reset.

SDSTOR-26141

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (dev/v8.x@4d93ef5). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/lib/blkalloc/bitmap_blk_allocator.cpp	50.00%	0 Missing and 3 partials ⚠️
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff             @@
##             dev/v8.x     #939   +/-   ##
===========================================
  Coverage            ?   49.12%           
===========================================
  Files               ?      112           
  Lines               ?    12797           
  Branches            ?     6068           
===========================================
  Hits                ?     6287           
  Misses              ?     2473           
  Partials            ?     4037           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[raakella1]

LG!