anonvma: when setting up page->mapping, we need to pick the _oldest_ anonvma

[deliverable/linux.git] / mm / rmap.c

diff --git a/mm/rmap.c b/mm/rmap.c
index ee97d38ed7d9ffcb45686e3395cd87d3b26b872b..4bad3267537a8c7826d313afa661a03f51b2df26 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -734,9 +734,20 @@ void page_move_anon_rmap(struct page *page,
 static void __page_set_anon_rmap(struct page *page,
        struct vm_area_struct *vma, unsigned long address)
 {
-       struct anon_vma *anon_vma = vma->anon_vma;
+       struct anon_vma_chain *avc;
+       struct anon_vma *anon_vma;
+
+       BUG_ON(!vma->anon_vma);
+
+       /*
+        * We must use the _oldest_ possible anon_vma for the page mapping!
+        *
+        * So take the last AVC chain entry in the vma, which is the deepest
+        * ancestor, and use the anon_vma from that.
+        */
+       avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma);
+       anon_vma = avc->anon_vma;
 
-       BUG_ON(!anon_vma);
        anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
        page->mapping = (struct address_space *) anon_vma;
        page->index = linear_page_index(vma, address);