rmap: move exclusively owned pages to own anon_vma in do_wp_page()

[linux-2.6-block.git] / mm / rmap.c

diff --git a/mm/rmap.c b/mm/rmap.c
index 23ecd0a892df600665f618aabd1ba2f522bc6387..28bcdc433d88cfd95f58fdb0cc6633ede583bfac 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -715,6 +715,30 @@ 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