Re: [PATCH v2 4/8] mm/memory_hotplug: Create memory block devices after arch_add_memory()

David Hildenbrand
2019-05-07T21:27:17Z

>> +static void unregister_memory(struct memory_block *memory)
>> +{
>> + BUG_ON(memory->dev.bus != &memory_subsys);
>
> Given this should never happen and only a future kernel developer
> might trip over it, do we really need to kill that developer's
> machine? I.e. s/BUG/WARN/? I guess an argument can be made to move
> such a change that to a follow-on patch since you're just preserving
> existing behavior, but I figure might as well address these as the
> code is refactored.

I assume only

if (WARN ...)
return;

makes sense then, right?

>
>> +
>> + /* drop the ref. we got via find_memory_block() */
>> + put_device(&memory->dev);
>> + device_unregister(&memory->dev);
>> +}
>> +
>> /*
>> - * need an interface for the VM to add new memory regions,
>> - * but without onlining it.
>> + * Create memory block devices for the given memory area. Start and size
>> + * have to be aligned to memory block granularity. Memory block devices
>> + * will be initialized as offline.
>> */
>> -int hotplug_memory_register(int nid, struct mem_section *section)
>> +int hotplug_memory_register(unsigned long start, unsigned long size)
>> {
>> - int ret = 0;
>> + unsigned long block_nr_pages = memory_block_size_bytes() >> PAGE_SHIFT;
>> + unsigned long start_pfn = PFN_DOWN(start);
>> + unsigned long end_pfn = start_pfn + (size >> PAGE_SHIFT);
>> + unsigned long pfn;
>> struct memory_block *mem;
>> + int ret = 0;
>>
>> - mutex_lock(&mem_sysfs_mutex);
>> + BUG_ON(!IS_ALIGNED(start, memory_block_size_bytes()));
>> + BUG_ON(!IS_ALIGNED(size, memory_block_size_bytes()));
>
> Perhaps:
>
> if (WARN_ON(...))
> return -EINVAL;
>

Yes, guess this souldn't hurt.

>>
>> - mem = find_memory_block(section);
>> - if (mem) {
>> - mem->section_count++;
>> - put_device(&mem->dev);
>> - } else {
>> - ret = init_memory_block(&mem, section, MEM_OFFLINE);
>> + mutex_lock(&mem_sysfs_mutex);
>> + for (pfn = start_pfn; pfn != end_pfn; pfn += block_nr_pages) {
>> + mem = find_memory_block(__pfn_to_section(pfn));
>> + if (mem) {
>> + WARN_ON_ONCE(false);
>
> ?? Isn't that a nop?

Yes, that makes no sense :)

Thanks!

--

Thanks,

David / dhildenb