cpu: fix node state for whether it contains CPU

cpu: fix node state for whether it contains CPU

In current kernel code, we only call node_set_state(cpu_to_node(cpu),
N_CPU) when a cpu is hot plugged.  But we do not set the node state for
N_CPU when the cpus are brought online during boot.

So this could lead to failure when we check to see if a node contains
cpu with node_state(node_id, N_CPU).

One use case is in the node_reclaime function:

        /*
         * Only run node reclaim on the local node or on nodes that do
         * not
         * have associated processors. This will favor the local
         * processor
         * over remote processors and spread off node memory allocations
         * as wide as possible.
         */
        if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id !=
                numa_node_id())
                return NODE_RECLAIM_NOSCAN;

I instrumented the kernel to call this function after boot and it always
returns 0 on a x86 desktop machine until I apply the attached patch.

   int num_cpu_node(void)
   {
       int i, nr_cpu_nodes = 0;

       for_each_node(i) {
               if (node_state(i, N_CPU))
                       ++ nr_cpu_nodes;
       }

       return nr_cpu_nodes;
   }

Fix this by checking each node for online CPU when we initialize
vmstat that's responsible for maintaining node state.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Tim Chen <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: <[email protected]>
Cc: Ying <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>