linux-kernel - [PATCH 6/6] mm: migrate: remove redundant page count check for THP

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Date:   Mon, 29 Mar 2021 11:33:12 -0700
From:   Yang Shi <shy828301@...il.com>
To:     mgorman@...e.de, kirill.shutemov@...ux.intel.com, ziy@...dia.com,
        mhocko@...e.com, ying.huang@...el.com, hughd@...gle.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com, borntraeger@...ibm.com,
        akpm@...ux-foundation.org
Cc:     shy828301@...il.com, linux-mm@...ck.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 6/6] mm: migrate: remove redundant page count check for THP

Don't have to keep the redundant page count check for THP anymore after
switching to use generic migration code.

Signed-off-by: Yang Shi <shy828301@...il.com>
---
 mm/migrate.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 1c0c873375ab..328f76848d6c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2097,18 +2097,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
 	if (isolate_lru_page(page))
 		return 0;
 
-	/*
-	 * migrate_misplaced_transhuge_page() skips page migration's usual
-	 * check on page_count(), so we must do it here, now that the page
-	 * has been isolated: a GUP pin, or any other pin, prevents migration.
-	 * The expected page count is 3: 1 for page's mapcount and 1 for the
-	 * caller's pin and 1 for the reference taken by isolate_lru_page().
-	 */
-	if (PageTransHuge(page) && page_count(page) != 3) {
-		putback_lru_page(page);
-		return 0;
-	}
-
 	page_lru = page_is_file_lru(page);
 	mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
 				thp_nr_pages(page));
-- 
2.26.2