Re: [PATCH v1 1/4] resource: Use PFN_UP / PFN_DOWN in walk_system_ram_range()

[Michal Hocko]

On Fri 09-08-19 14:56:58, David Hildenbrand wrote:
> This makes it clearer that we will never call func() with duplicate PFNs
> in case we have multiple sub-page memory resources. All unaligned parts
> of PFNs are completely discarded.
> 
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Nadav Amit <namit@xxxxxxxxxx>
> Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  kernel/resource.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 7ea4306503c5..88ee39fa9103 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -487,8 +487,8 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
>  	while (start < end &&
>  	       !find_next_iomem_res(start, end, flags, IORES_DESC_NONE,
>  				    false, &res)) {
> -		pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT;
> -		end_pfn = (res.end + 1) >> PAGE_SHIFT;
> +		pfn = PFN_UP(res.start);
> +		end_pfn = PFN_DOWN(res.end + 1);
>  		if (end_pfn > pfn)
>  			ret = (*func)(pfn, end_pfn - pfn, arg);
>  		if (ret)
> -- 
> 2.21.0

-- 
Michal Hocko
SUSE Labs