1 files changed, 24 insertions, 0 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 23ecd0a892df..28bcdc433d88 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -716,6 +716,30 @@ int page_mkclean(struct page *page)
 EXPORT_SYMBOL_GPL(page_mkclean);
 
 /**
+ * page_move_anon_rmap - move a page to our anon_vma
+ * @page:       the page to move to our anon_vma
+ * @vma:        the vma the page belongs to
+ * @address:    the user virtual address mapped
+ *
+ * When a page belongs exclusively to one process after a COW event,
+ * that page can be moved into the anon_vma that belongs to just that
+ * process, so the rmap code will not search the parent or sibling
+ * processes.
+ */
+void page_move_anon_rmap(struct page *page,
+        struct vm_area_struct *vma, unsigned long address)
+{
+        struct anon_vma *anon_vma = vma->anon_vma;
+
+        VM_BUG_ON(!PageLocked(page));
+        VM_BUG_ON(!anon_vma);
+        VM_BUG_ON(page->index != linear_page_index(vma, address));
+
+        anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+        page->mapping = (struct address_space *) anon_vma;
+}
+
+/**
  * __page_set_anon_rmap - setup new anonymous rmap
  * @page:       the page to add the mapping to
  * @vma:        the vm area in which the mapping is added