mempolicy: write lock mmap_sem while changing task mempolicy

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

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index ce2c5b6bf9f86722cafd03aab8e0fe725e12bf61..c6c61ea6bb8ca827ea308dcf71ca51d398337a0f 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -591,16 +591,29 @@ static long do_set_mempolicy(unsigned short mode, unsigned short flags,
                             nodemask_t *nodes)
 {
        struct mempolicy *new;
+       struct mm_struct *mm = current->mm;
 
        new = mpol_new(mode, flags, nodes);
        if (IS_ERR(new))
                return PTR_ERR(new);
+
+       /*
+        * prevent changing our mempolicy while show_numa_maps()
+        * is using it.
+        * Note:  do_set_mempolicy() can be called at init time
+        * with no 'mm'.
+        */
+       if (mm)
+               down_write(&mm->mmap_sem);
        mpol_put(current->mempolicy);
        current->mempolicy = new;
        mpol_set_task_struct_flag();
        if (new && new->policy == MPOL_INTERLEAVE &&
            nodes_weight(new->v.nodes))
                current->il_next = first_node(new->v.nodes);
+       if (mm)
+               up_write(&mm->mmap_sem);
+
        return 0;
 }
 
@@ -1566,15 +1579,15 @@ struct page *alloc_pages_current(gfp_t gfp, unsigned order)
 EXPORT_SYMBOL(alloc_pages_current);
 
 /*
- * If mpol_copy() sees current->cpuset == cpuset_being_rebound, then it
+ * If mpol_dup() sees current->cpuset == cpuset_being_rebound, then it
  * rebinds the mempolicy its copying by calling mpol_rebind_policy()
  * with the mems_allowed returned by cpuset_mems_allowed().  This
  * keeps mempolicies cpuset relative after its cpuset moves.  See
  * further kernel/cpuset.c update_nodemask().
  */
 
-/* Slow path of a mempolicy copy */
-struct mempolicy *__mpol_copy(struct mempolicy *old)
+/* Slow path of a mempolicy duplicate */
+struct mempolicy *__mpol_dup(struct mempolicy *old)
 {
        struct mempolicy *new = kmem_cache_alloc(policy_cache, GFP_KERNEL);