mm/huge_memory: fix page_trans_huge_mapcount assumption of THP size

Ask the page what size it is instead of assuming it's PMD size.

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>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Link: https://lkml.kernel.org/r/20200908195539.25896-7-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 5934ef7..6fb75df 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2558,14 +2558,14 @@ int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
        page = compound_head(page);
 
        _total_mapcount = ret = 0;
-       for (i = 0; i < HPAGE_PMD_NR; i++) {
+       for (i = 0; i < thp_nr_pages(page); i++) {
                mapcount = atomic_read(&page[i]._mapcount) + 1;
                ret = max(ret, mapcount);
                _total_mapcount += mapcount;
        }
        if (PageDoubleMap(page)) {
                ret -= 1;
-               _total_mapcount -= HPAGE_PMD_NR;
+               _total_mapcount -= thp_nr_pages(page);
        }
        mapcount = compound_mapcount(page);
        ret += mapcount;