Unnecessary cloning in BufferMgr.unpinAll

[SLMT]

There is an unnecessary cloning in org.vanilladb.core.storage.buffer.BufferMgr. Here is the code snippet:

private void unpinAll(Transaction tx) {
	// Copy the set of pinned buffers to avoid ConcurrentModificationException
	Set<PinningBuffer> pinnedBuffs = new HashSet<PinningBuffer>(pinningBuffers.values());
	if (pinnedBuffs != null) {
		for (PinningBuffer pinnedBuff : pinnedBuffs)
			bufferPool.unpin(pinnedBuff.buffer);
	}

	synchronized (bufferPool) {
		bufferPool.notifyAll();
	}
}

This may be a legacy code that used to prevent ConcurrentModificationExeception, but this became unnecessary as we updated the logic of the code in the past.