Re: [RESEND PATCH] mm/sparsemem: use wrapped macros instead of open-coding

[John Hubbard <jhubbard@nvidia.com>]

On 3/6/20 2:19 AM, qiwuchen55@gmail.com wrote:
> From: chenqiwu <chenqiwu@xiaomi.com>
> 
> Use wrapped macros instead of open-coding for better code
> readability.
> 
> Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>


This breaks my x86 (64-bit) build:

mm/sparse.c: In function ‘check_usemap_section_nr’:
mm/sparse.c:389:33: error: implicit declaration of function ‘virt_to_pfn’; did you mean ‘virt_to_phys’? [-Werror=implicit-function-declaration]
  389 |  usemap_snr = pfn_to_section_nr(virt_to_pfn(usage));
      |                                 ^~~~~~~~~~~
      |                                 virt_to_phys


...and I think the reason is that the arch/x86/include/asm/page.h does not
have virt_to_pfn(). For that reason, I'm concerned that the following fix, 
which fixes up x86, may not completely correct for the patch.

Here's a compile-tested (only, and only on x86 64-bit) fix:

diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index 7555b48803a8..982bc76bf13c 100644
--- a/arch/x86/include/asm/page.h
+++ b/arch/x86/include/asm/page.h
@@ -62,6 +62,9 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr,
 #define __boot_va(x)		__va(x)
 #define __boot_pa(x)		__pa(x)
 
+#define virt_to_pfn(kaddr)	(__pa(kaddr) >> PAGE_SHIFT)
+#define pfn_to_virt(pfn)	__va((pfn) << PAGE_SHIFT)
+
 /*
  * virt_to_page(kaddr) returns a valid pointer if and only if
  * virt_addr_valid(kaddr) returns true.


thanks,
-- 
John Hubbard
NVIDIA

> ---
>  mm/sparse.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 42c18a3..9b14164 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -385,8 +385,8 @@ static void __init check_usemap_section_nr(int nid,
>  		old_pgdat_snr = NR_MEM_SECTIONS;
>  	}
>  
> -	usemap_snr = pfn_to_section_nr(__pa(usage) >> PAGE_SHIFT);
> -	pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
> +	usemap_snr = pfn_to_section_nr(virt_to_pfn(usage));
> +	pgdat_snr = pfn_to_section_nr(virt_to_pfn(pgdat));
>  	if (usemap_snr == pgdat_snr)
>  		return;
>  
> @@ -677,7 +677,7 @@ struct page * __meminit populate_section_memmap(unsigned long pfn,
>  
>  	return NULL;
>  got_map_page:
> -	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
> +	ret = (struct page *)page_to_virt(page);
>  got_map_ptr:
>  
>  	return ret;
>