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Subject[PATCH v4 25/36] mm: Fix total_mapcount assumption of page size
Date
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 7a5e2b470bc7..15a86b06befc 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2668,7 +2668,7 @@ 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);

@@ -2676,16 +2676,17 @@ 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;
}

--
2.26.2
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