mm: migrate: remove THP mapcount check in numamigrate_isolate_page()

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migration"), which is out of date, since migrate_misplaced_page() is now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@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index d1b8ab5a241719ded7b59964b399ca5cb56e2470..0030703204d3ef4eda32069e8ce14c35fad910d3 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2486,10 +2486,6 @@ 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;