X Transition to all VMA under 1 fileh to be either all based on wcfs or all based on !wcfs
This allows to make decision to drop a page right after writeout for wcfs case. If vmas for one fileh were allowed to be mixed - we could not know whether to drop the page & its memory from RAM or not - even if there is no vma mapped in !wcfs mode, it could be created later, and by dropping RAM cahce we hit severe slowness. NOTE: in between transactions there is usually no vmas mapped, so this case is not artificial. By requiring that all VMAs are of the same kind under one fileh we avoid this ambiguity.
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