kthread: ensure locality of task_struct allocations

In the presence of memoryless nodes, numa_node_id() will return the
current CPU's NUMA node, but that may not be where we expect to allocate
from memory from.  Instead, we should rely on the fallback code in the
memory allocator itself, by using NUMA_NO_NODE.  Also, when calling
kthread_create_on_node(), use the nearest node with memory to the cpu in
question, rather than the node it is running on.

Signed-off-by: Nishanth Aravamudan <[email protected]>
Reviewed-by: Christoph Lameter <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Anton Blanchard <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Ben Herrenschmidt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Nishanth Aravamudan

kernel/kthread.c

@@ -217,7 +217,7 @@ int tsk_fork_get_node(struct task_struct *tsk)
 	if (tsk == kthreadd_task)
 		return tsk->pref_node_fork;
 #endif
-	return numa_node_id();
+	return NUMA_NO_NODE;
 }
 
 static void create_kthread(struct kthread_create_info *create)
@@ -369,7 +369,7 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
 {
 	struct task_struct *p;
 
-	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
+	p = kthread_create_on_node(threadfn, data, cpu_to_mem(cpu), namefmt,
 				   cpu);
 	if (IS_ERR(p))
 		return p;