mm: prevent endless growth of anon_vma hierarchy

[cascardo/linux.git] / include / linux / rmap.h

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index c0c2bce..d9d7e7e 100644 (file)
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -36,6 +36,16 @@ struct anon_vma {
         */
        atomic_t refcount;
 
+       /*
+        * Count of child anon_vmas and VMAs which points to this anon_vma.
+        *
+        * This counter is used for making decision about reusing anon_vma
+        * instead of forking new one. See comments in function anon_vma_clone.
+        */
+       unsigned degree;
+
+       struct anon_vma *parent;        /* Parent of this anon_vma */
+
        /*
         * NOTE: the LSB of the rb_root.rb_node is set by
         * mm_take_all_locks() _after_ taking the above lock. So the