In preparation for using insert_page() for DAX, enhance
insert_page_into_pte_locked() to handle establishing writable
mappings. Recall that DAX returns VM_FAULT_NOPAGE after installing a
PTE which bypasses the typical set_pte_range() in finish_fault.
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>