1 files changed, 16 insertions, 9 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 1ea4e6fcee77..059774712c08 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -659,23 +659,30 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma)
                 }
 
                 /*
-                 * It would be tidy to reset the PageAnon mapping here,
-                 * but that might overwrite a racing page_add_anon_rmap
-                 * which increments mapcount after us but sets mapping
-                 * before us: so leave the reset to free_hot_cold_page,
-                 * and remember that it's only reliable while mapped.
-                 * Leaving it set also helps swapoff to reinstate ptes
-                 * faster for those pages still in swapcache.
+                 * Now that the last pte has gone, s390 must transfer dirty
+                 * flag from storage key to struct page.  We can usually skip
+                 * this if the page is anon, so about to be freed; but perhaps
+                 * not if it's in swapcache - there might be another pte slot
+                 * containing the swap entry, but page not yet written to swap.
                  */
                 if ((!PageAnon(page) || PageSwapCache(page)) &&
                     page_test_dirty(page)) {
                         page_clear_dirty(page);
                         set_page_dirty(page);
                 }
-                mem_cgroup_uncharge_page(page);
 
+                mem_cgroup_uncharge_page(page);
                 __dec_zone_page_state(page,
-                                PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
+                        PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
+                /*
+                 * It would be tidy to reset the PageAnon mapping here,
+                 * but that might overwrite a racing page_add_anon_rmap
+                 * which increments mapcount after us but sets mapping
+                 * before us: so leave the reset to free_hot_cold_page,
+                 * and remember that it's only reliable while mapped.
+                 * Leaving it set also helps swapoff to reinstate ptes
+                 * faster for those pages still in swapcache.
+                 */
         }
 }