[022/156] mm/huge_memory: fix total_mapcount assumption of page size

Commit Message

Andrew Morton Oct. 16, 2020, 2:42 a.m. UTC

From: "Kirill A. Shutemov" <[e-mail]>
Subject: mm/huge_memory: fix total_mapcount assumption of page size

File THPs may now be of arbitrary order.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kirill A. Shutemov <[e-mail]>
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Reviewed-by: SeongJae Park <[e-mail]>
Cc: Huang Ying <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/huge_memory.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Patch

--- a/mm/huge_memory.c~mm-huge_memory-fix-total_mapcount-assumption-of-page-size
+++ a/mm/huge_memory.c
@@ -2494,7 +2494,7 @@  static void __split_huge_page(struct pag
 
 int total_mapcount(struct page *page)
 {
-	int i, compound, ret;
+	int i, compound, nr, ret;
 
 	VM_BUG_ON_PAGE(PageTail(page), page);
 
@@ -2502,16 +2502,17 @@  int total_mapcount(struct page *page)
 		return atomic_read(&page->_mapcount) + 1;
 
 	compound = compound_mapcount(page);
+	nr = compound_nr(page);
 	if (PageHuge(page))
 		return compound;
 	ret = compound;
-	for (i = 0; i < HPAGE_PMD_NR; i++)
+	for (i = 0; i < nr; i++)
 		ret += atomic_read(&page[i]._mapcount) + 1;
 	/* File pages has compound_mapcount included in _mapcount */
 	if (!PageAnon(page))
-		return ret - compound * HPAGE_PMD_NR;
+		return ret - compound * nr;
 	if (PageDoubleMap(page))
-		ret -= HPAGE_PMD_NR;
+		ret -= nr;
 	return ret;
 }