IN  PEPROCESS Process,
  IN  PVOID VirtualAddress

Routine Description:

    This procedure ensures that a physical page is available on
    the zeroed, free or standby list such that the next call the remove a
    page absolutely will not block.  This is necessary as blocking would
    require a wait which could cause a deadlock condition.

    If a page is available the function returns immediately with a value
    of FALSE indicating no wait operation was performed.  If no physical
    page is available, the thread enters a wait state and the function
    returns the value TRUE when the wait operation completes.


    Process - Supplies a pointer to the current process if, and only if,
              the working set mutex is held currently held and should
              be released if a wait operation is issued.  Supplies
              the value NULL otherwise.

    VirtualAddress - Supplies the virtual address for the faulting page.
                     If the value is NULL, the page is treated as a
                     user mode address.

Return Value:

    FALSE - if a page was immediately available.
    TRUE - if a wait operation occurred before a page became available.


    Must be holding the PFN database mutex with APCs disabled.