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

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Date:   Wed, 14 Aug 2019 17:41:05 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        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: [PATCH v2 1/5] resource: Use PFN_UP / PFN_DOWN in walk_system_ram_range()

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>
---
 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