mm/huge_memory: fix total_mapcount assumption of page size

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: SeongJae Park <sjpark@amazon.de>
Cc: Huang Ying <ying.huang@intel.com>
Link: https://lkml.kernel.org/r/20200908195539.25896-5-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index aa612cc..b63c985 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2494,7 +2494,7 @@ 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);
 
@@ -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;
 }