linux-kernel - [Patch v2] mm/sparsemem: get address to page struct instead of address to pfn

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Date:   Mon, 10 Feb 2020 08:50:48 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     akpm@...ux-foundation.org, osalvador@...e.de,
        dan.j.williams@...el.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Wei Yang <richardw.yang@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Baoquan He <bhe@...hat.com>
Subject: [Patch v2] mm/sparsemem: get address to page struct instead of address to pfn

memmap should be the address to page struct instead of address to pfn.

As mentioned by David, if system memory and devmem sit within a
section, the mismatch address would lead kdump to dump unexpected
memory.

Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
valid to get the page struct address at this point.

Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
CC: Dan Williams <dan.j.williams@...el.com>
CC: David Hildenbrand <david@...hat.com>
CC: Baoquan He <bhe@...hat.com>

---
v2:
  * adjust comment to mention the mismatch data would affect kdump

---
 mm/sparse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 586d85662978..4862ec2cfbc0 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 
 	/* Align memmap to section boundary in the subsection case */
 	if (section_nr_to_pfn(section_nr) != start_pfn)
-		memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
+		memmap = pfn_to_page(section_nr_to_pfn(section_nr));
 	sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
 
 	return 0;
-- 
2.17.1