linux-kernel - Re: [PATCH 4/4] arch, mm: make kernel_page

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Date:   Mon, 26 Oct 2020 00:54:01 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH 4/4] arch, mm: make kernel_page_present() always available

On Sun, 2020-10-25 at 12:15 +0200, Mike Rapoport wrote:
> index 7f248fc45317..16f878c26667 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -2228,7 +2228,6 @@ void __kernel_map_pages(struct page *page, int
> numpages, int enable)
>  }
>  #endif /* CONFIG_DEBUG_PAGEALLOC */
>  
> -#ifdef CONFIG_HIBERNATION
>  bool kernel_page_present(struct page *page)
>  {
>         unsigned int level;
> @@ -2240,7 +2239,6 @@ bool kernel_page_present(struct page *page)
>         pte = lookup_address((unsigned long)page_address(page),
> &level);
>         return (pte_val(*pte) & _PAGE_PRESENT);
>  }
> -#endif /* CONFIG_HIBERNATION */

This is only used by hibernate today right? Makes sense that it should
return a correct answer if someone starts to use it without looking too
closely at the header. But could we just remove the default static
inline return true implementation and let the linker fail if someone
starts to use it outside hibernate? Then we could leave it compiled out
until then.

Also it looks like riscv does not have ARCH_HIBERNATION_POSSIBLE so the
new function added here couldn't be used yet. You could also just let
the linker catch it if riscv ever enables hibernate?