[CASSANDRA-18311] BufferPool incorrectly counts memoryInUse when putUnusedPortion is used

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 4.0.9, 4.1.1, 5.0-alpha1, 5.0
• Component/s: Local/Caching
• Bug Category: Correctness
• Severity: Low
• Complexity: Low Hanging Fruit
• Discovered By: User Report
• Platform: All
• Since Version: 4.0

Source Control Link

https://github.com/apache/cassandra/commit/3cfb2221223a7631f116108aec0a45646e775705

Test and Documentation Plan

regression tests + new test

• Assignee: Jaroslaw Grabowski
• Reporter: Jaroslaw Grabowski

Authors

Jaroslaw Grabowski

Reviewers

Jacek Lewandowski

• Created: 09/Mar/23 11:33
• Updated: 12/Sep/23 13:03
• Resolved: 13/Mar/23 09:09

Description

The counter is incorrectly decremented by the size of the unused portion of the provided buffer.
It should be decremented by the number of bytes actually returned to the pool (that may be different than "size"). The number should be calculated as a difference between original and resulting buffer capacity.