linux-kernel - Re: [PATCH v2 1/5] resource: Use PFN_UP / PFN_DOWN in walk_system_ram

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Message-ID: <20190814161541.ho5b6ju4t23vruff@master>
Date:   Wed, 14 Aug 2019 16:15:41 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Dan Williams <dan.j.williams@...el.com>,
        Borislav Petkov <bp@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Nadav Amit <namit@...are.com>,
        Wei Yang <richardw.yang@...ux.intel.com>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v2 1/5] resource: Use PFN_UP / PFN_DOWN in
 walk_system_ram_range()

On Wed, Aug 14, 2019 at 05:41:05PM +0200, 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@...el.com>
>Cc: Borislav Petkov <bp@...e.de>
>Cc: Andrew Morton <akpm@...ux-foundation.org>
>Cc: Bjorn Helgaas <bhelgaas@...gle.com>
>Cc: Ingo Molnar <mingo@...nel.org>
>Cc: Dave Hansen <dave.hansen@...ux.intel.com>
>Cc: Nadav Amit <namit@...are.com>
>Cc: Wei Yang <richardw.yang@...ux.intel.com>
>Cc: Oscar Salvador <osalvador@...e.de>
>Acked-by: Michal Hocko <mhocko@...e.com>
>Signed-off-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Wei Yang <richardw.yang@...ux.intel.com>

>---
> 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

-- 
Wei Yang
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