2 files changed, 23 insertions, 34 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 332f5c29b53a..66e65ab39426 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -138,8 +138,8 @@ config SPLIT_PTLOCK_CPUS
 #
 config MIGRATION
         bool "Page migration"
-        def_bool y if NUMA
-        depends on SWAP && NUMA
+        def_bool y
+        depends on NUMA
         help
           Allows the migration of the physical location of pages of processes
           while the virtual addresses are not changed. This is useful for
diff --git a/mm/migrate.c b/mm/migrate.c
index 81721a061d50..8f91463eab4e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -254,14 +254,20 @@ static int migrate_page_move_mapping(struct address_space *mapping,
 {
         struct page **radix_pointer;
 
+        if (!mapping) {
+                /* Anonymous page */
+                if (page_count(page) != 1)
+                        return -EAGAIN;
+                return 0;
+        }
+
         write_lock_irq(&mapping->tree_lock);
 
         radix_pointer = (struct page **)radix_tree_lookup_slot(
                                                 &mapping->page_tree,
                                                 page_index(page));
 
-        if (!page_mapping(page) ||
-                        page_count(page) != 2 + !!PagePrivate(page) ||
+        if (page_count(page) != 2 + !!PagePrivate(page) ||
                         *radix_pointer != page) {
                 write_unlock_irq(&mapping->tree_lock);
                 return -EAGAIN;
@@ -271,10 +277,12 @@ static int migrate_page_move_mapping(struct address_space *mapping,
          * Now we know that no one else is looking at the page.
          */
         get_page(newpage);
+#ifdef CONFIG_SWAP
         if (PageSwapCache(page)) {
                 SetPageSwapCache(newpage);
                 set_page_private(newpage, page_private(page));
         }
+#endif
 
         *radix_pointer = newpage;
         __put_page(page);
@@ -308,7 +316,9 @@ static void migrate_page_copy(struct page *newpage, struct page *page)
                 set_page_dirty(newpage);
         }
 
+#ifdef CONFIG_SWAP
         ClearPageSwapCache(page);
+#endif
         ClearPageActive(page);
         ClearPagePrivate(page);
         set_page_private(page, 0);
@@ -353,16 +363,6 @@ int migrate_page(struct address_space *mapping,
                 return rc;
 
         migrate_page_copy(newpage, page);
-
-        /*
-         * Remove auxiliary swap entries and replace
-         * them with real ptes.
-         *
-         * Note that a real pte entry will allow processes that are not
-         * waiting on the page lock to use the new page via the page tables
-         * before the new page is unlocked.
-         */
-        remove_from_swap(newpage);
         return 0;
 }
 EXPORT_SYMBOL(migrate_page);
@@ -530,23 +530,7 @@ redo:
                                 goto unlock_page;
 
                 /*
-                 * Establish swap ptes for anonymous pages or destroy pte
-                 * maps for files.
-                 *
-                 * In order to reestablish file backed mappings the fault handlers
-                 * will take the radix tree_lock which may then be used to stop
-                 * processses from accessing this page until the new page is ready.
-                 *
-                 * A process accessing via a swap pte (an anonymous page) will take a
-                 * page_lock on the old page which will block the process until the
-                 * migration attempt is complete. At that time the PageSwapCache bit
-                 * will be examined. If the page was migrated then the PageSwapCache
-                 * bit will be clear and the operation to retrieve the page will be
-                 * retried which will find the new page in the radix tree. Then a new
-                 * direct mapping may be generated based on the radix tree contents.
-                 *
-                 * If the page was not migrated then the PageSwapCache bit
-                 * is still set and the operation may continue.
+                 * Establish migration ptes or remove ptes
                  */
                 rc = -EPERM;
                 if (try_to_unmap(page, 1) == SWAP_FAIL)
@@ -569,9 +553,9 @@ redo:
                  */
                 mapping = page_mapping(page);
                 if (!mapping)
-                        goto unlock_both;
+                        rc = migrate_page(mapping, newpage, page);
 
-                if (mapping->a_ops->migratepage)
+                else if (mapping->a_ops->migratepage)
                         /*
                          * Most pages have a mapping and most filesystems
                          * should provide a migration function. Anonymous
@@ -584,10 +568,15 @@ redo:
                 else
                         rc = fallback_migrate_page(mapping, newpage, page);
 
-unlock_both:
+                if (!rc)
+                        remove_migration_ptes(page, newpage);
+
                 unlock_page(newpage);
 
 unlock_page:
+                if (rc)
+                        remove_migration_ptes(page, page);
+
                 unlock_page(page);
 
 next: