mm/migration: remove some duplicated codes in migrate_pages

Remove the duplicated codes in migrate_pages to simplify the code.  Minor
readability improvement.  No functional change intended.

Link: https://lkml.kernel.org/r/20220318111709.60311-9-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/migrate.c

@@ -1410,14 +1410,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 						nr_thp_split++;
 						goto retry;
 					}
-
-					nr_failed_pages += nr_subpages;
-					break;
-				}
-
 				/* Hugetlb migration is unsupported */
-				if (!no_subpage_counting)
+				} else if (!no_subpage_counting) {
 					nr_failed++;
+				}
+
 				nr_failed_pages += nr_subpages;
 				break;
 			case -ENOMEM:
@@ -1432,28 +1429,22 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 						nr_thp_split++;
 						goto retry;
 					}
-
-					nr_failed_pages += nr_subpages;
-					goto out;
+				} else if (!no_subpage_counting) {
+					nr_failed++;
 				}
 
-				if (!no_subpage_counting)
-					nr_failed++;
 				nr_failed_pages += nr_subpages;
 				goto out;
 			case -EAGAIN:
-				if (is_thp) {
+				if (is_thp)
 					thp_retry++;
-					break;
-				}
-				retry++;
+				else
+					retry++;
 				break;
 			case MIGRATEPAGE_SUCCESS:
 				nr_succeeded += nr_subpages;
-				if (is_thp) {
+				if (is_thp)
 					nr_thp_succeeded++;
-					break;
-				}
 				break;
 			default:
 				/*
@@ -1462,14 +1453,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				 * removed from migration page list and not
 				 * retried in the next outer loop.
 				 */
-				if (is_thp) {
+				if (is_thp)
 					nr_thp_failed++;
-					nr_failed_pages += nr_subpages;
-					break;
-				}
-
-				if (!no_subpage_counting)
+				else if (!no_subpage_counting)
 					nr_failed++;
+
 				nr_failed_pages += nr_subpages;
 				break;
 			}