On Sat, 28 May 2011, Michal Hocko wrote:

quoted

--- a/include/linux/nodemask.h~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-fix-2
+++ a/include/linux/nodemask.h

@@ -433,8 +433,6 @@ static inline void node_set_offline(int 
 	nr_online_nodes = num_node_state(N_ONLINE);
 }
 
-extern int node_random(const nodemask_t *maskp);
-
 #else
 
 static inline int node_state(int node, enum node_states state)

@@ -466,7 +464,15 @@ static inline int num_node_state(enum no
 #define node_set_online(node)	   node_set_state((node), N_ONLINE)
 #define node_set_offline(node)	   node_clear_state((node), N_ONLINE)
 
-static inline int node_random(const nodemask_t *mask) { return 0; }
+#endif
+
+#if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1)
+extern int node_random(const nodemask_t *maskp);
+#else
+static inline int node_random(const nodemask_t *mask)
+{
+	return 0;
+}
 #endif

I have to admit that I quite don't understand concept of several nodes
with UMA archs but do we really want to provide the sane node all the
time?

They aren't nodes on UMA machines, they are memory regions for 
DISCONTIGMEM which are separated by large holes in the address space.  
These archs will never sanely use node_random(), so it doesn't really 
matter except for CONFIG_NUMA where MAX_NUMNODES > 1, since they won't be 
selecting random memory regions.

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