mm: compaction: fix the migration stats in trace_mm_compaction_migratepages()

Now the migrate_pages() has changed to return the number of {normal
page, THP, hugetlb} instead, thus we should not use the return value to
calculate the number of pages migrated successfully.  Instead we can
just use the 'nr_succeeded' which indicates the number of normal pages
migrated successfully to calculate the non-migrated pages in
trace_mm_compaction_migratepages().

Link: https://lkml.kernel.org/r/b4225251c4bec068dcd90d275ab7de88a39e2bd7.1636275127.git.baolin.wang@linux.alibaba.comSigned-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/trace/events/compaction.h

@@ -68,10 +68,9 @@ DEFINE_EVENT(mm_compaction_isolate_template, mm_compaction_isolate_freepages,
 TRACE_EVENT(mm_compaction_migratepages,
 
 	TP_PROTO(unsigned long nr_all,
-		int migrate_rc,
-		struct list_head *migratepages),
+		unsigned int nr_succeeded),
 
-	TP_ARGS(nr_all, migrate_rc, migratepages),
+	TP_ARGS(nr_all, nr_succeeded),
 
 	TP_STRUCT__entry(
 		__field(unsigned long, nr_migrated)
@@ -79,23 +78,8 @@ TRACE_EVENT(mm_compaction_migratepages,
 	),
 
 	TP_fast_assign(
-		unsigned long nr_failed = 0;
-		struct list_head *page_lru;
-
-		/*
-		 * migrate_pages() returns either a non-negative number
-		 * with the number of pages that failed migration, or an
-		 * error code, in which case we need to count the remaining
-		 * pages manually
-		 */
-		if (migrate_rc >= 0)
-			nr_failed = migrate_rc;
-		else
-			list_for_each(page_lru, migratepages)
-				nr_failed++;
-
-		__entry->nr_migrated = nr_all - nr_failed;
-		__entry->nr_failed = nr_failed;
+		__entry->nr_migrated = nr_succeeded;
+		__entry->nr_failed = nr_all - nr_succeeded;
 	),
 
 	TP_printk("nr_migrated=%lu nr_failed=%lu",

mm/compaction.c

@@ -2280,6 +2280,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
 	unsigned long last_migrated_pfn;
 	const bool sync = cc->mode != MIGRATE_ASYNC;
 	bool update_cached;
+	unsigned int nr_succeeded = 0;
 
 	/*
 	 * These counters track activities during zone compaction.  Initialize
@@ -2398,10 +2399,10 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
 
 		err = migrate_pages(&cc->migratepages, compaction_alloc,
 				compaction_free, (unsigned long)cc, cc->mode,
-				MR_COMPACTION, NULL);
+				MR_COMPACTION, &nr_succeeded);
 
-		trace_mm_compaction_migratepages(cc->nr_migratepages, err,
-							&cc->migratepages);
+		trace_mm_compaction_migratepages(cc->nr_migratepages,
+						 nr_succeeded);
 
 		/* All pages were either migrated or will be released */
 		cc->nr_migratepages = 0;