[PATCH 1/3] mm/sparsemem: adjust memmap only for SPARSEMEM_VMEMMAP

[Wei Yang]

Only when SPARSEMEM_VMEMMAP is set, memmap returned from
section_activate() points to sub-section page struct. Otherwise, memmap
already points to the whole section page struct.

This means only for SPARSEMEM_VMEMMAP, we need to adjust memmap for
sub-section case.

Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
CC: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 mm/sparse.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 586d85662978..b5da121bdd6e 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -886,7 +886,8 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 	section_mark_present(ms);
 
 	/* Align memmap to section boundary in the subsection case */
-	if (section_nr_to_pfn(section_nr) != start_pfn)
+	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) &&
+		section_nr_to_pfn(section_nr) != start_pfn)
 		memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
 	sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
 
-- 
2.17.1