Re: [PATCH V13 4/4] LoongArch: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 26/10/22 14:59, Huacai Chen wrote:
> On Mon, Oct 24, 2022 at 4:04 PM Guo Ren <guoren@kernel.org> wrote:
>> On Mon, Oct 24, 2022 at 3:05 PM Huacai Chen <chenhuacai@loongson.cn> wrote:
>>>
>>> From: Feiyang Chen <chenfeiyang@loongson.cn>
>>>
>>> The feature of minimizing overhead of struct page associated with each
>>> HugeTLB page is implemented on x86_64. However, the infrastructure of
>>> this feature is already there, so just select ARCH_WANT_HUGETLB_PAGE_
>>> OPTIMIZE_VMEMMAP is enough to enable this feature for LoongArch.
>>>
>>> To avoid the following build error on LoongArch we should include linux/
>>> static_key.h in page-flags.h. This is straightforward but the build
>>> error is implicitly a LoongArch-specific problem, because ARM64 and X86
>>> have already include static_key.h from their arch-specific core headers.

>>> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
>>> index 0b0ae5084e60..1aafdc73e399 100644
>>> --- a/include/linux/page-flags.h
>>> +++ b/include/linux/page-flags.h
>>> @@ -9,6 +9,7 @@
>>>   #include <linux/types.h>
>>>   #include <linux/bug.h>
>>>   #include <linux/mmdebug.h>
>>> +#include <linux/static_key.h>
>> Em... riscv needn't this.

Would guarding the header suffice and make riscv OK with this patch?

  #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
  #include <linux/static_key.h>
  #endif

> I found that after 36d4b36b69590fed99356a4426c940a25 (" lib/nodemask:
> inline next_node_in() and node_random()"), build errors have gone. But
> I think this is just an accident. Because that commit adds random.h
> inclusion in nodemask.h, then asm-offsets.c --> sched.h --> nodemask.h
> --> random.h --> once.h --> jump_label.h. If one day this chain is
> adjusted, then build errors come again.
> 
> On the other hand, page-flags.h is obviously using some static_key
> macros, including static_key.h is straightforward for building.
> 
> Huacai