[PATCH v4] mm/page_vma_mapped.c: Explicitly compare pfn for normal, hugetlbfs and THP page

[Li Xinhai <lixinhai.lxh@gmail.com>]

When check_pte, pfn of normal, hugetlbfs and THP page need be compared.
The current implementation apply comparison as
- normal 4K page: page_pfn <= pfn < page_pfn + 1
- hugetlbfs page:  page_pfn <= pfn < page_pfn + HPAGE_PMD_NR
- THP page: page_pfn <= pfn < page_pfn + HPAGE_PMD_NR
in pfn_in_hpage. For hugetlbfs page, it should be
page_pfn == pfn

Now, change pfn_in_hpage to pfn_is_match to highlight that comparison
is not only for THP and explicitly compare for these cases.

Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/page_vma_mapped.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index eff4b45..719c352 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -52,12 +52,16 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw)
 	return true;
 }
 
-static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn)
+static inline bool pfn_is_match(struct page *page, unsigned long pfn)
 {
-	unsigned long hpage_pfn = page_to_pfn(hpage);
+	unsigned long page_pfn = page_to_pfn(page);
+
+	/* normal page and hugetlbfs page */
+	if (!PageTransCompound(page) || PageHuge(page))
+		return page_pfn == pfn;
 
 	/* THP can be referenced by any subpage */
-	return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage);
+	return pfn >= page_pfn && pfn - page_pfn < hpage_nr_pages(page);
 }
 
 /**
@@ -108,7 +112,7 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw)
 		pfn = pte_pfn(*pvmw->pte);
 	}
 
-	return pfn_in_hpage(pvmw->page, pfn);
+	return pfn_is_match(pvmw->page, pfn);
 }
 
 /**
-- 
1.8.3.1