mm/huge_memory: fix total_mapcount assumption of page size

File THPs may now be of arbitrary order. Signed-off-by: Kirill A. Shutemov <[email protected]> Signed-off-by: Matthew Wilcox (Oracle) <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Reviewed-by: SeongJae Park <[email protected]> Cc: Huang Ying <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Linus Torvalds <[email protected]>
ashr · Oct 16, 2020 · 86b562b · 86b562b
1 parent 8fb156c
commit 86b562b
Showing 1 changed file with 5 additions and 4 deletions.
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
@@ -2494,24 +2494,25 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 
 int total_mapcount(struct page *page)
 {
-	int i, compound, ret;
+	int i, compound, nr, ret;
 
 	VM_BUG_ON_PAGE(PageTail(page), page);
 
 	if (likely(!PageCompound(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;
 }