[PATCH v3 2/8] mm: migrate: remove THP mapcount check in numamigrate_isolate_page()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

The check of THP mapped by multiple processes was introduced by commit
04fa5d6a6547 ("mm: migrate: check page_count of THP before migrating")
and refactor by commit 340ef3902cf2 ("mm: numa: cleanup flow of transhuge
page migration"), which is out of date, since migrate_misplaced_page()
is now using the standard migrate_pages() for small pages and THPs, the
reference count checking is in folio_migrate_mapping(), so let's remove
the special check for THP.

Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 mm/migrate.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 646d8ee7f102..f2d86dfd8423 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2483,10 +2483,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
 	int nr_pages = thp_nr_pages(page);
 	int order = compound_order(page);
 
-	/* Do not migrate THP mapped by multiple processes */
-	if (PageTransHuge(page) && total_mapcount(page) > 1)
-		return 0;
-
 	/* Avoid migrating to a node that is nearly full */
 	if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
 		int z;
-- 
2.27.0