Re: [RFC Patch V1 01/30] mm, kernel: Use cpu_to_mem()/numa_mem_id() to support memoryless node

Hi Paul,

On 11.07.2014 [08:14:05 -0700], Paul E. McKenney wrote:
> On Fri, Jul 11, 2014 at 03:37:18PM +0800, Jiang Liu wrote:
> > When CONFIG_HAVE_MEMORYLESS_NODES is enabled, cpu_to_node()/numa_node_id()
> > may return a node without memory, and later cause system failure/panic
> > when calling kmalloc_node() and friends with returned node id.
> > So use cpu_to_mem()/numa_mem_id() instead to get the nearest node with
> > memory for the/current cpu.
> > 
> > If CONFIG_HAVE_MEMORYLESS_NODES is disabled, cpu_to_mem()/numa_mem_id()
> > is the same as cpu_to_node()/numa_node_id().
> > 
> > Signed-off-by: Jiang Liu <[email protected]>
> 
> For the rcutorture piece:
> 
> Acked-by: Paul E. McKenney <[email protected]>
> 
> Or if you separate the kernel/rcu/rcutorture.c portion into a separate
> patch, I will queue it separately.

Just FYI, based upon a separate discussion with Tejun and others, it
seems to be preferred to avoid the proliferation of cpu_to_mem
throughout the kernel blindly. For kthread_create_on_node(), I'm going
to try and fix the underlying issue and so you, as the caller, should
still specify the NUMA node you are running the kthread on
(cpu_to_node), not where you expect the memory to come from
(cpu_to_mem).

Thanks,
Nish