mm: clean up page_remove_rmap()

page_remove_rmap() has multiple PageAnon() tests and it has deep nesting.
Clean this up.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 27 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 0895b5c7cbf..1406e67f961 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -739,34 +739,37 @@ void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long
  */
 void page_remove_rmap(struct page *page)
 {
-        if (atomic_add_negative(-1, &page->_mapcount)) {
-                /*
-                 * 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);
-                }
-                if (PageAnon(page))
-                        mem_cgroup_uncharge_page(page);
-                __dec_zone_page_state(page,
-                        PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
-                mem_cgroup_update_mapped_file_stat(page, -1);
-                /*
-                 * 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.
-                 */
+        /* page still mapped by someone else? */
+        if (!atomic_add_negative(-1, &page->_mapcount))
+                return;
+
+        /*
+         * 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);
         }
+        if (PageAnon(page)) {
+                mem_cgroup_uncharge_page(page);
+                __dec_zone_page_state(page, NR_ANON_PAGES);
+        } else {
+                __dec_zone_page_state(page, NR_FILE_MAPPED);
+        }
+        mem_cgroup_update_mapped_file_stat(page, -1);
+        /*
+         * 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.
+         */
 }
 
 /*