x86, 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.

static 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;
}

I have not tested other architectues but they are likely to have similar issue.

Signed-off-by Tim Chen <[email protected]>

---
 arch/x86/kernel/smpboot.c | 1 +
 1 file changed, 1 insertion(+)

arch/x86/kernel/smpboot.c +0 -0

index d8f7d01..04c0574 100644

Quoted 7 lines · Tim Chen

Signed-off-by Tim Chen <[email protected]>

---
 arch/x86/kernel/smpboot.c | 1 +

 1 file changed, 1 insertion(+)

arch/x86/kernel/smpboot.c static void notrace start_secondary(void *unused) · line 265

Quoted 12 lines

arch/x86/kernel/smpboot.c +1 -0

index d8f7d01..04c0574 100644
@@ -259,6 +259,7 @@ static void notrace start_secondary(void *unused)
  	lock_vector_lock();
  	setup_vector_irq(smp_processor_id());
  	set_cpu_online(smp_processor_id(), true);
+	node_set_state(cpu_to_node(smp_processor_id()), N_CPU);
  	unlock_vector_lock();
  	cpu_set_state_online(smp_processor_id());
  	x86_platform.nmi_init();

Would it not be easier to register the vmstat_notifier earlier, before SMP bringup? Because with this change, we need to go fix all architectures.