mm/vmscan.c: support removing arbitrary sized pages from mapping

__remove_mapping() assumes that pages can only be either base pages or
HPAGE_PMD_SIZE.  Ask the page what size it is.

Link: http://lkml.kernel.org/r/20191017164223.2762148-4-songliubraving@fb.com
Fixes: 7b7f7e485f82 ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 024b7e92975230dafe32f7b032e0c63895c6fc56..ee4eecc7e1c2177041d00d8eb8d62ca64647206a 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -933,10 +933,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
         * Note that if SetPageDirty is always performed via set_page_dirty,
         * and thus under the i_pages lock, then this ordering is not required.
         */
-       if (unlikely(PageTransHuge(page)) && PageSwapCache(page))
-               refcount = 1 + HPAGE_PMD_NR;
-       else
-               refcount = 2;
+       refcount = 1 + compound_nr(page);
        if (!page_ref_freeze(page, refcount))
                goto cannot_free;
        /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */