[PATCH v4 5/6] mm/nvdimm: Use correct alignment when looking at first pfn from a region

[Aneesh Kumar K.V]

vmem_altmap_offset() adjust the section aligned base_pfn offset.
So we need to make sure we account for the same when computing base_pfn.

ie, for altmap_valid case, our pfn_first should be:

pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap);

Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
 kernel/memremap.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index a0e5f6b91b04..63800128844b 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -58,9 +58,11 @@ static unsigned long pfn_first(struct dev_pagemap *pgmap)
        struct vmem_altmap *altmap = &pgmap->altmap;
        unsigned long pfn;
 
-       pfn = PHYS_PFN(res->start);
-       if (pgmap->altmap_valid)
-               pfn += vmem_altmap_offset(altmap);
+       if (pgmap->altmap_valid) {
+               pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
+       } else
+               pfn = PHYS_PFN(res->start);
+
        return pfn;
 }
 
-- 
2.21.0