[PATCH 04/11] mm/huge_memory: Fix total_mapcount assumption of page size

Matthew Wilcox (Oracle)
2020-09-08T19:56:12Z

From: "Kirill A. Shutemov" <kirill@shutemov.name>

File THPs may now be of arbitrary order.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
mm/huge_memory.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index adc5a91d8fd4..a882d770a812 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2458,7 +2458,7 @@ 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);

@@ -2466,16 +2466,17 @@ 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;
}

--
2.28.0