[HDDS-2523] BufferPool.releaseBuffer may release a buffer different than the head of the list

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.5.0
• Component/s: Ozone Client
• Labels: pull-request-available
• Assignee: Attila Doroszlai
• Reporter: Tsz-wo Sze
• Created: 18/Nov/19 00:07
• Updated: 24/Feb/20 20:54
• Resolved: 20/Nov/19 20:50

Description

//BufferPool
  public void releaseBuffer(ByteBuffer byteBuffer) {
    // always remove from head of the list and append at last
    ByteBuffer buffer = bufferList.remove(0);
    // Ensure the buffer to be removed is always at the head of the list.
    Preconditions.checkArgument(buffer.equals(byteBuffer));
    buffer.clear();
    bufferList.add(buffer);
    Preconditions.checkArgument(currentBufferIndex >= 0);
    currentBufferIndex--;
  }

In the code above, it expects buffer and byteBuffer are the same object, i.e. buffer == byteBuffer. However the precondition is checking buffer.equals(byteBuffer). Unfortunately, both buffer and byteBuffer have remaining() == 0 so that equals(..) returns true and the precondition does not catch the bug.

Issue Links

• links to: GitHub Pull Request #232