+ /*
+ * Take out anonymous pages first, anonymous shared vmas are
+ * not dirty accountable.
+ */
+ if (PageAnon(old_page)) {
+ if (!TestSetPageLocked(old_page)) {
+ reuse = can_share_swap_page(old_page);
+ unlock_page(old_page);
+ }
+ } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
+ (VM_WRITE|VM_SHARED))) {
+ /*
+ * Only catch write-faults on shared writable pages,
+ * read-only shared pages can get COWed by
+ * get_user_pages(.write=1, .force=1).
+ */