3 files changed, 24 insertions, 20 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 47e6e2f21e21..4a55f35a6ced 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -582,11 +582,11 @@ static int hugetlbfs_migrate_page(struct address_space *mapping,
         int rc;
 
         rc = migrate_huge_page_move_mapping(mapping, newpage, page);
-        if (rc)
+        if (rc != MIGRATEPAGE_SUCCESS)
                 return rc;
         migrate_page_copy(newpage, page);
 
-        return 0;
+        return MIGRATEPAGE_SUCCESS;
 }
 
 static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index ce7e6671968b..a4e886d17f87 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -7,6 +7,13 @@
 
 typedef struct page *new_page_t(struct page *, unsigned long private, int **);
 
+/*
+ * Return values from addresss_space_operations.migratepage():
+ * - negative errno on page migration failure;
+ * - zero on page migration success;
+ */
+#define MIGRATEPAGE_SUCCESS             0
+
 #ifdef CONFIG_MIGRATION
 
 extern void putback_lru_pages(struct list_head *l);
diff --git a/mm/migrate.c b/mm/migrate.c
index 1dc4598d2513..33f5f82a6006 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -276,7 +276,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
                 /* Anonymous page without mapping */
                 if (page_count(page) != 1)
                         return -EAGAIN;
-                return 0;
+                return MIGRATEPAGE_SUCCESS;
         }
 
         spin_lock_irq(&mapping->tree_lock);
@@ -346,7 +346,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
         }
         spin_unlock_irq(&mapping->tree_lock);
 
-        return 0;
+        return MIGRATEPAGE_SUCCESS;
 }
 
 /*
@@ -362,7 +362,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
         if (!mapping) {
                 if (page_count(page) != 1)
                         return -EAGAIN;
-                return 0;
+                return MIGRATEPAGE_SUCCESS;
         }
 
         spin_lock_irq(&mapping->tree_lock);
@@ -389,7 +389,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
         page_unfreeze_refs(page, expected_count - 1);
 
         spin_unlock_irq(&mapping->tree_lock);
-        return 0;
+        return MIGRATEPAGE_SUCCESS;
 }
 
 /*
@@ -476,11 +476,11 @@ int migrate_page(struct address_space *mapping,
 
         rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
 
-        if (rc)
+        if (rc != MIGRATEPAGE_SUCCESS)
                 return rc;
 
         migrate_page_copy(newpage, page);
-        return 0;
+        return MIGRATEPAGE_SUCCESS;
 }
 EXPORT_SYMBOL(migrate_page);
 
@@ -503,7 +503,7 @@ int buffer_migrate_page(struct address_space *mapping,
 
         rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
 
-        if (rc)
+        if (rc != MIGRATEPAGE_SUCCESS)
                 return rc;
 
         /*
@@ -539,7 +539,7 @@ int buffer_migrate_page(struct address_space *mapping,
 
         } while (bh != head);
 
-        return 0;
+        return MIGRATEPAGE_SUCCESS;
 }
 EXPORT_SYMBOL(buffer_migrate_page);
 #endif
@@ -618,7 +618,7 @@ static int fallback_migrate_page(struct address_space *mapping,
  *
  * Return value:
  *   < 0 - error code
- *  == 0 - success
+ *  MIGRATEPAGE_SUCCESS - success
  */
 static int move_to_new_page(struct page *newpage, struct page *page,
                                 int remap_swapcache, enum migrate_mode mode)
@@ -655,7 +655,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
         else
                 rc = fallback_migrate_page(mapping, newpage, page, mode);
 
-        if (rc) {
+        if (rc != MIGRATEPAGE_SUCCESS) {
                 newpage->mapping = NULL;
         } else {
                 if (remap_swapcache)
@@ -804,7 +804,7 @@ skip_unmap:
                 put_anon_vma(anon_vma);
 
 uncharge:
-        mem_cgroup_end_migration(mem, page, newpage, rc == 0);
+        mem_cgroup_end_migration(mem, page, newpage, rc == MIGRATEPAGE_SUCCESS);
 unlock:
         unlock_page(page);
 out:
@@ -977,7 +977,7 @@ int migrate_pages(struct list_head *from,
                         case -EAGAIN:
                                 retry++;
                                 break;
-                        case 0:
+                        case MIGRATEPAGE_SUCCESS:
                                 break;
                         default:
                                 /* Permanent failure */
@@ -986,15 +986,12 @@ int migrate_pages(struct list_head *from,
                         }
                 }
         }
-        rc = 0;
+        rc = nr_failed + retry;
 out:
         if (!swapwrite)
                 current->flags &= ~PF_SWAPWRITE;
 
-        if (rc)
-                return rc;
-
-        return nr_failed + retry;
+        return rc;
 }
 
 int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
@@ -1014,7 +1011,7 @@ int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
                         /* try again */
                         cond_resched();
                         break;
-                case 0:
+                case MIGRATEPAGE_SUCCESS:
                         goto out;
                 default:
                         rc = -EIO;