[PATCH 3/3] mm/sparse: use __highest_present_section_nr as the boundary for pfn check

[Wei Yang <richard.weiyang@gmail.com>]

And it is known, __highest_present_section_nr is a more strict boundary
than NR_MEM_SECTIONS.

This patch uses a __highest_present_section_nr to check a valid pfn.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
---
 include/linux/mmzone.h | 4 ++--
 mm/sparse.c            | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 33086f86d1a7..5138efde11ae 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1237,7 +1237,7 @@ extern int __highest_present_section_nr;
 #ifndef CONFIG_HAVE_ARCH_PFN_VALID
 static inline int pfn_valid(unsigned long pfn)
 {
-	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
+	if (pfn_to_section_nr(pfn) > __highest_present_section_nr)
 		return 0;
 	return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
 }
@@ -1245,7 +1245,7 @@ static inline int pfn_valid(unsigned long pfn)
 
 static inline int pfn_present(unsigned long pfn)
 {
-	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
+	if (pfn_to_section_nr(pfn) > __highest_present_section_nr)
 		return 0;
 	return present_section(__nr_to_section(pfn_to_section_nr(pfn)));
 }
diff --git a/mm/sparse.c b/mm/sparse.c
index 90bab7f03757..a9c55c8da11f 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -174,6 +174,7 @@ void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
  * those loops early.
  */
 int __highest_present_section_nr;
+EXPORT_SYMBOL(__highest_present_section_nr);
 static void section_mark_present(struct mem_section *ms)
 {
 	int section_nr = __section_nr(ms);
-- 
2.15.1