[PATCH v2 10/16] mm/huge_memory: check pmd_present first in is_huge_zero_pmd

[Miaohe Lin]

When pmd is non-present, pmd_pfn returns an insane value. So we should
check pmd_present first to avoid acquiring such insane value and also
avoid touching possible cold huge_zero_pfn cache line when pmd isn't
present.

Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 include/linux/huge_mm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index ae3d8e2fd9e2..12b297f9951d 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -273,7 +273,7 @@ static inline bool is_huge_zero_page(struct page *page)
 
 static inline bool is_huge_zero_pmd(pmd_t pmd)
 {
-	return READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd) && pmd_present(pmd);
+	return pmd_present(pmd) && READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd);
 }
 
 static inline bool is_huge_zero_pud(pud_t pud)
-- 
2.23.0