On Tue 10-09-19 20:47:40, Yunsheng Lin wrote: > On 2019/9/10 19:12, Greg KH wrote: > > On Tue, Sep 10, 2019 at 01:04:51PM +0200, Michal Hocko wrote: > >> On Tue 10-09-19 18:58:05, Yunsheng Lin wrote: > >>> On 2019/9/10 17:31, Greg KH wrote: > >>>> On Tue, Sep 10, 2019 at 02:43:32PM +0800, Yunsheng Lin wrote: > >>>>> On 2019/9/9 17:53, Greg KH wrote: > >>>>>> On Mon, Sep 09, 2019 at 02:04:23PM +0800, Yunsheng Lin wrote: > >>>>>>> Currently a device does not belong to any of the numa nodes > >>>>>>> (dev->numa_node is NUMA_NO_NODE) when the node id is neither > >>>>>>> specified by fw nor by virtual device layer and the device has > >>>>>>> no parent device. > >>>>>> > >>>>>> Is this really a problem? > >>>>> > >>>>> Not really. > >>>>> Someone need to guess the node id when it is not specified, right? > >>>> > >>>> No, why? Guessing guarantees you will get it wrong on some systems. > >>>> > >>>> Are you seeing real problems because the id is not being set? What > >>>> problem is this fixing that you can actually observe? > >>> > >>> When passing the return value of dev_to_node() to cpumask_of_node() > >>> without checking the node id if the node id is not valid, there is > >>> global-out-of-bounds detected by KASAN as below: > >> > >> OK, I seem to remember this being brought up already. And now when I > >> think about it, we really want to make cpumask_of_node NUMA_NO_NODE > >> aware. That means using the same trick the allocator does for this > >> special case. > > > > That seems reasonable to me, and much more "obvious" as to what is going > > on. > > > > Ok, thanks for the suggestion. > > For arm64 and x86, there are two versions of cpumask_of_node(). > > when CONFIG_DEBUG_PER_CPU_MAPS is defined, the cpumask_of_node() > in arch/x86/mm/numa.c is used, which does partial node id checking: > > const struct cpumask *cpumask_of_node(int node) > { > if (node >= nr_node_ids) { > printk(KERN_WARNING > "cpumask_of_node(%d): node > nr_node_ids(%u)\n", > node, nr_node_ids); > dump_stack(); > return cpu_none_mask; > } > if (node_to_cpumask_map[node] == NULL) { > printk(KERN_WARNING > "cpumask_of_node(%d): no node_to_cpumask_map!\n", > node); > dump_stack(); > return cpu_online_mask; > } > return node_to_cpumask_map[node]; > } > > when CONFIG_DEBUG_PER_CPU_MAPS is undefined, the cpumask_of_node() > in arch/x86/include/asm/topology.h is used: > > static inline const struct cpumask *cpumask_of_node(int node) > { > return node_to_cpumask_map[node]; > }
I would simply go with. There shouldn't be any need for heavy weight checks that CONFIG_DEBUG_PER_CPU_MAPS has. static inline const struct cpumask *cpumask_of_node(int node) { /* A nice comment goes here */ if (node == NUMA_NO_NODE) return node_to_cpumask_map[numa_mem_id()]; return node_to_cpumask_map[node]; } -- Michal Hocko SUSE Labs