mm: mempolicy: Check for misplaced page

[mirror_ubuntu-artful-kernel.git] / mm / mempolicy.c

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index c21e91477c4f0b7dff91f50f16bbdc7242b806ce..df1466d3d2d868091b1558719fc676516e0508f3 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2181,6 +2181,82 @@ static void sp_free(struct sp_node *n)
        kmem_cache_free(sn_cache, n);
 }
 
+/**
+ * mpol_misplaced - check whether current page node is valid in policy
+ *
+ * @page   - page to be checked
+ * @vma    - vm area where page mapped
+ * @addr   - virtual address where page mapped
+ *
+ * Lookup current policy node id for vma,addr and "compare to" page's
+ * node id.
+ *
+ * Returns:
+ *     -1      - not misplaced, page is in the right node
+ *     node    - node id where the page should be
+ *
+ * Policy determination "mimics" alloc_page_vma().
+ * Called from fault path where we know the vma and faulting address.
+ */
+int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long addr)
+{
+       struct mempolicy *pol;
+       struct zone *zone;
+       int curnid = page_to_nid(page);
+       unsigned long pgoff;
+       int polnid = -1;
+       int ret = -1;
+
+       BUG_ON(!vma);
+
+       pol = get_vma_policy(current, vma, addr);
+       if (!(pol->flags & MPOL_F_MOF))
+               goto out;
+
+       switch (pol->mode) {
+       case MPOL_INTERLEAVE:
+               BUG_ON(addr >= vma->vm_end);
+               BUG_ON(addr < vma->vm_start);
+
+               pgoff = vma->vm_pgoff;
+               pgoff += (addr - vma->vm_start) >> PAGE_SHIFT;
+               polnid = offset_il_node(pol, vma, pgoff);
+               break;
+
+       case MPOL_PREFERRED:
+               if (pol->flags & MPOL_F_LOCAL)
+                       polnid = numa_node_id();
+               else
+                       polnid = pol->v.preferred_node;
+               break;
+
+       case MPOL_BIND:
+               /*
+                * allows binding to multiple nodes.
+                * use current page if in policy nodemask,
+                * else select nearest allowed node, if any.
+                * If no allowed nodes, use current [!misplaced].
+                */
+               if (node_isset(curnid, pol->v.nodes))
+                       goto out;
+               (void)first_zones_zonelist(
+                               node_zonelist(numa_node_id(), GFP_HIGHUSER),
+                               gfp_zone(GFP_HIGHUSER),
+                               &pol->v.nodes, &zone);
+               polnid = zone->node;
+               break;
+
+       default:
+               BUG();
+       }
+       if (curnid != polnid)
+               ret = polnid;
+out:
+       mpol_cond_put(pol);
+
+       return ret;
+}
+
 static void sp_delete(struct shared_policy *sp, struct sp_node *n)
 {
        pr_debug("deleting %lx-l%lx\n", n->start, n->end);