linux-kernel - [PATCH 1/3] mm/sparsemem: adjust memmap only for SPARSEMEM

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Message-Id: <20200206231629.14151-2-richardw.yang@linux.intel.com>
Date:   Fri,  7 Feb 2020 07:16:27 +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, bhe@...hat.com,
        david@...hat.com, Wei Yang <richardw.yang@...ux.intel.com>
Subject: [PATCH 1/3] mm/sparsemem: adjust memmap only for SPARSEMEM_VMEMMAP

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@...ux.intel.com>
CC: Dan Williams <dan.j.williams@...el.com>
---
 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