This patch prevents btbulkdelete() from calling WriteNoReleaseBuffer()
several times for the same buffer. Thus it saves a few
LWLockAquire(BufMgrLock, LW_EXCLUSIVE) and LWLockRelease(BufMgrLock)
calls.
Maybe we do not need a BufMgrLock at all, because we have a super
exclusive lock on the buffer? I was not sure and decided to stay on
the safe side ...
Servus
Manfred