[PATCH -v4 1/9] migrate_pages: organize stats with struct migrate_pages_stats

[Huang Ying <ying.huang@intel.com>]

Define struct migrate_pages_stats to organize the various statistics
in migrate_pages().  This makes it easier to collect and consume the
statistics in multiple functions.  This will be needed in the
following patches in the series.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Bharata B Rao <bharata@amd.com>
Cc: haoxin <xhao@linux.alibaba.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
 mm/migrate.c | 60 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 26 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index a4d3fc65085f..ef388a9e4747 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1396,6 +1396,16 @@ static inline int try_split_folio(struct folio *folio, struct list_head *split_f
 	return rc;
 }
 
+struct migrate_pages_stats {
+	int nr_succeeded;	/* Normal and large folios migrated successfully, in
+				   units of base pages */
+	int nr_failed_pages;	/* Normal and large folios failed to be migrated, in
+				   units of base pages.  Untried folios aren't counted */
+	int nr_thp_succeeded;	/* THP migrated successfully */
+	int nr_thp_failed;	/* THP failed to be migrated */
+	int nr_thp_split;	/* THP split before migrating */
+};
+
 /*
  * migrate_pages - migrate the folios specified in a list, to the free folios
  *		   supplied as the target for the page migration
@@ -1430,13 +1440,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 	int large_retry = 1;
 	int thp_retry = 1;
 	int nr_failed = 0;
-	int nr_failed_pages = 0;
 	int nr_retry_pages = 0;
-	int nr_succeeded = 0;
-	int nr_thp_succeeded = 0;
 	int nr_large_failed = 0;
-	int nr_thp_failed = 0;
-	int nr_thp_split = 0;
 	int pass = 0;
 	bool is_large = false;
 	bool is_thp = false;
@@ -1446,9 +1451,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 	LIST_HEAD(split_folios);
 	bool nosplit = (reason == MR_NUMA_MISPLACED);
 	bool no_split_folio_counting = false;
+	struct migrate_pages_stats stats;
 
 	trace_mm_migrate_pages_start(mode, reason);
 
+	memset(&stats, 0, sizeof(stats));
 split_folio_migration:
 	for (pass = 0; pass < 10 && (retry || large_retry); pass++) {
 		retry = 0;
@@ -1502,9 +1509,9 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				/* Large folio migration is unsupported */
 				if (is_large) {
 					nr_large_failed++;
-					nr_thp_failed += is_thp;
+					stats.nr_thp_failed += is_thp;
 					if (!try_split_folio(folio, &split_folios)) {
-						nr_thp_split += is_thp;
+						stats.nr_thp_split += is_thp;
 						break;
 					}
 				/* Hugetlb migration is unsupported */
@@ -1512,7 +1519,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 					nr_failed++;
 				}
 
-				nr_failed_pages += nr_pages;
+				stats.nr_failed_pages += nr_pages;
 				list_move_tail(&folio->lru, &ret_folios);
 				break;
 			case -ENOMEM:
@@ -1522,13 +1529,13 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				 */
 				if (is_large) {
 					nr_large_failed++;
-					nr_thp_failed += is_thp;
+					stats.nr_thp_failed += is_thp;
 					/* Large folio NUMA faulting doesn't split to retry. */
 					if (!nosplit) {
 						int ret = try_split_folio(folio, &split_folios);
 
 						if (!ret) {
-							nr_thp_split += is_thp;
+							stats.nr_thp_split += is_thp;
 							break;
 						} else if (reason == MR_LONGTERM_PIN &&
 							   ret == -EAGAIN) {
@@ -1546,7 +1553,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 					nr_failed++;
 				}
 
-				nr_failed_pages += nr_pages + nr_retry_pages;
+				stats.nr_failed_pages += nr_pages + nr_retry_pages;
 				/*
 				 * There might be some split folios of fail-to-migrate large
 				 * folios left in split_folios list. Move them back to migration
@@ -1556,7 +1563,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				list_splice_init(&split_folios, from);
 				/* nr_failed isn't updated for not used */
 				nr_large_failed += large_retry;
-				nr_thp_failed += thp_retry;
+				stats.nr_thp_failed += thp_retry;
 				goto out;
 			case -EAGAIN:
 				if (is_large) {
@@ -1568,8 +1575,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				nr_retry_pages += nr_pages;
 				break;
 			case MIGRATEPAGE_SUCCESS:
-				nr_succeeded += nr_pages;
-				nr_thp_succeeded += is_thp;
+				stats.nr_succeeded += nr_pages;
+				stats.nr_thp_succeeded += is_thp;
 				break;
 			default:
 				/*
@@ -1580,20 +1587,20 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				 */
 				if (is_large) {
 					nr_large_failed++;
-					nr_thp_failed += is_thp;
+					stats.nr_thp_failed += is_thp;
 				} else if (!no_split_folio_counting) {
 					nr_failed++;
 				}
 
-				nr_failed_pages += nr_pages;
+				stats.nr_failed_pages += nr_pages;
 				break;
 			}
 		}
 	}
 	nr_failed += retry;
 	nr_large_failed += large_retry;
-	nr_thp_failed += thp_retry;
-	nr_failed_pages += nr_retry_pages;
+	stats.nr_thp_failed += thp_retry;
+	stats.nr_failed_pages += nr_retry_pages;
 	/*
 	 * Try to migrate split folios of fail-to-migrate large folios, no
 	 * nr_failed counting in this round, since all split folios of a
@@ -1626,16 +1633,17 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 	if (list_empty(from))
 		rc = 0;
 
-	count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
-	count_vm_events(PGMIGRATE_FAIL, nr_failed_pages);
-	count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded);
-	count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed);
-	count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split);
-	trace_mm_migrate_pages(nr_succeeded, nr_failed_pages, nr_thp_succeeded,
-			       nr_thp_failed, nr_thp_split, mode, reason);
+	count_vm_events(PGMIGRATE_SUCCESS, stats.nr_succeeded);
+	count_vm_events(PGMIGRATE_FAIL, stats.nr_failed_pages);
+	count_vm_events(THP_MIGRATION_SUCCESS, stats.nr_thp_succeeded);
+	count_vm_events(THP_MIGRATION_FAIL, stats.nr_thp_failed);
+	count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split);
+	trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages,
+			       stats.nr_thp_succeeded, stats.nr_thp_failed,
+			       stats.nr_thp_split, mode, reason);
 
 	if (ret_succeeded)
-		*ret_succeeded = nr_succeeded;
+		*ret_succeeded = stats.nr_succeeded;
 
 	return rc;
 }
-- 
2.35.1