linux-kernel - [PATCH v2] mm/migrate: correct thp migration stats.

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Date:   Thu, 17 Sep 2020 17:04:13 -0400
From:   Zi Yan <zi.yan@...t.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Zi Yan <ziy@...dia.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: [PATCH v2] mm/migrate: correct thp migration stats.

From: Zi Yan <ziy@...dia.com>

PageTransHuge returns true for both thp and hugetlb, so thp stats was
counting both thp and hugetlb migrations. Exclude hugetlb migration by
setting is_thp variable right.

Clean up thp handling code too when we are there.

Fixes: 1a5bae25e3cf ("mm/vmstat: add events for THP migration without split")
Signed-off-by: Zi Yan <ziy@...dia.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@...cle.com>
Cc: Daniel Jordan <daniel.m.jordan@...cle.com>
Cc: Anshuman Khandual <anshuman.khandual@....com>
---
 mm/migrate.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 941b89383cf3..6bc9559afc70 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1445,7 +1445,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 			 * Capture required information that might get lost
 			 * during migration.
 			 */
-			is_thp = PageTransHuge(page);
+			is_thp = PageTransHuge(page) && !PageHuge(page);
 			nr_subpages = thp_nr_pages(page);
 			cond_resched();
 
@@ -1471,7 +1471,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 				 * we encounter them after the rest of the list
 				 * is processed.
 				 */
-				if (PageTransHuge(page) && !PageHuge(page)) {
+				if (is_thp) {
 					lock_page(page);
 					rc = split_huge_page_to_list(page, from);
 					unlock_page(page);
@@ -1480,8 +1480,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 						nr_thp_split++;
 						goto retry;
 					}
-				}
-				if (is_thp) {
+
 					nr_thp_failed++;
 					nr_failed += nr_subpages;
 					goto out;
-- 
2.28.0