[HMM 12/15] mm/migrate: allow migrate_vma() to alloc new page on empty entry v2

This allow caller of migrate_vma() to allocate new page for empty CPU page table entry. It only support anoymous memory and it won't allow new page to be instance if userfaultfd is armed. This is useful to device driver that want to migrate a range of virtual address and would rather allocate new

[HMM 12/15] mm/migrate: allow migrate_vma() to alloc new page on empty entry v2

This allow caller of migrate_vma() to allocate new page for empty CPU page table entry. It only support anoymous memory and it won't allow new page to be instance if userfaultfd is armed. This is useful to device driver that want to migrate a range of virtual address and would rather allocate new