[PATCH] Handle holes in node mask in node fallback list setup

Change the find_next_best_node algorithm to correctly skip
over holes in the node online mask. Previously it would not handle
missing nodes correctly and cause crashes at boot.

[Written by Linus, tested by AK]

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 11 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62c122528587..208812b25597 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1541,29 +1541,29 @@ static int __initdata node_load[MAX_NUMNODES];
  */
 static int __init find_next_best_node(int node, nodemask_t *used_node_mask)
 {
-        int i, n, val;
+        int n, val;
         int min_val = INT_MAX;
         int best_node = -1;
 
-        for_each_online_node(i) {
-                cpumask_t tmp;
+        /* Use the local node if we haven't already */
+        if (!node_isset(node, *used_node_mask)) {
+                node_set(node, *used_node_mask);
+                return node;
+        }
 
-                /* Start from local node */
-                n = (node+i) % num_online_nodes();
+        for_each_online_node(n) {
+                cpumask_t tmp;
 
                 /* Don't want a node to appear more than once */
                 if (node_isset(n, *used_node_mask))
                         continue;
 
-                /* Use the local node if we haven't already */
-                if (!node_isset(node, *used_node_mask)) {
-                        best_node = node;
-                        break;
-                }
-
                 /* Use the distance array to find the distance */
                 val = node_distance(node, n);
 
+                /* Penalize nodes under us ("prefer the next node") */
+                val += (n < node);
+
                 /* Give preference to headless and unused nodes */
                 tmp = node_to_cpumask(n);
                 if (!cpus_empty(tmp))