memory hotplug: migrate swap cache page

In test, some pages in swap-cache can't be migrated, as they aren't rmap.

unmap_and_move() ignores swap-cache page which is just read in and hasn't
rmap (see the comments in the code), but swap_aops provides .migratepage.
Better to migrate such pages instead of ignore them.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Yakui Zhao <yakui.zhao@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 939888f9ddab..0edeac91348d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -147,7 +147,7 @@ out:
 static void remove_file_migration_ptes(struct page *old, struct page *new)
 {
         struct vm_area_struct *vma;
-        struct address_space *mapping = page_mapping(new);
+        struct address_space *mapping = new->mapping;
         struct prio_tree_iter iter;
         pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 
@@ -664,13 +664,15 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
                          *    needs to be effective.
                          */
                         try_to_free_buffers(page);
+                        goto rcu_unlock;
                 }
-                goto rcu_unlock;
+                goto skip_unmap;
         }
 
         /* Establish migration ptes or remove ptes */
         try_to_unmap(page, 1);
 
+skip_unmap:
         if (!page_mapped(page))
                 rc = move_to_new_page(newpage, page);