[PATCHv11 04/37] mm, thp: adjust conditions when we can reuse the page on WP fault

With new refcounting we will be able map the same compound page with PTEs and PMDs. It requires adjustment to conditions when we can reuse the page on write-protection fault. For PTE fault we can't reuse the page if it's part of huge page. For PMD we can only reuse the page if nobody else maps

[PATCHv11 04/37] mm, thp: adjust conditions when we can reuse the page on WP fault

With new refcounting we will be able map the same compound page with PTEs and PMDs. It requires adjustment to conditions when we can reuse the page on write-protection fault. For PTE fault we can't reuse the page if it's part of huge page. For PMD we can only reuse the page if nobody else maps