[RFC PATCH 2/3] mm: migrate: Correct the hugetlb migration stats

[Baolin Wang <baolin.wang@linux.alibaba.com>]

Correct the migration stats for hugetlb with using compound_nr() instead
of thp_nr_pages(), meanwhile change 'nr_failed_pages' to record the
number of normal pages failed to migrate, including THP and hugetlb,
and 'nr_succeeded' will record the number of normal pages migrated
successfully.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/migrate.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 00b8922..00e231c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1436,7 +1436,8 @@ static inline int try_split_thp(struct page *page, struct page **page2,
  * It is caller's responsibility to call putback_movable_pages() to return pages
  * to the LRU or free list only if ret != 0.
  *
- * Returns the number of {normal page, THP} that were not migrated, or an error code.
+ * Returns the number of {normal page, THP, hugetlb} that were not migrated,
+ * or an error code.
  */
 int migrate_pages(struct list_head *from, new_page_t get_new_page,
 		free_page_t put_new_page, unsigned long private,
@@ -1476,7 +1477,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 			 * during migration.
 			 */
 			is_thp = PageTransHuge(page) && !PageHuge(page);
-			nr_subpages = thp_nr_pages(page);
+			nr_subpages = compound_nr(page);
 			cond_resched();
 
 			if (PageHuge(page))
@@ -1523,6 +1524,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				}
 
 				/* Hugetlb migration is unsupported */
+				nr_failed_pages++;
 				nr_failed++;
 				break;
 			case -ENOMEM:
@@ -1541,6 +1543,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 					nr_failed_pages += nr_subpages;
 					goto out;
 				}
+				nr_failed_pages += nr_subpages;
 				nr_failed++;
 				goto out;
 			case -EAGAIN:
@@ -1551,12 +1554,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				retry++;
 				break;
 			case MIGRATEPAGE_SUCCESS:
+				nr_succeeded += nr_subpages;
 				if (is_thp) {
 					nr_thp_succeeded++;
-					nr_succeeded += nr_subpages;
 					break;
 				}
-				nr_succeeded++;
 				break;
 			default:
 				/*
@@ -1565,9 +1567,9 @@ 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.
 				 */
+				nr_failed_pages += nr_subpages;
 				if (is_thp) {
 					nr_thp_failed++;
-					nr_failed_pages += nr_subpages;
 					break;
 				}
 				nr_failed++;
@@ -1576,7 +1578,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 		}
 	}
 	nr_failed += retry + thp_retry;
-	nr_failed_pages += nr_failed;
 	nr_thp_failed += thp_retry;
 	rc = nr_failed + nr_thp_failed;
 out:
-- 
1.8.3.1