[PATCH 6.6 06/60] mm: migrate: remove THP mapcount check in numamigrate_isolate_page()

[Sasha Levin]

From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>

[ Upstream commit 728be28fae8c838d52c91dce4867133798146357 ]

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migration"), which is out of date, since migrate_misplaced_page() is now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.

Link: https://lkml.kernel.org/r/20230913095131.2426871-3-wangkefeng.wang@xxxxxxxxxx
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Suggested-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Stable-dep-of: 2774f256e7c0 ("mm/vmscan: fix a bug calling wakeup_kswapd() with a wrong zone index")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/migrate.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 6f8ad6b64c9bc..c9fabb960996f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2506,10 +2506,6 @@ 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;
-- 
2.43.0