From: Muchun Song Date: Fri, 5 Feb 2021 02:32:17 +0000 (-0800) Subject: mm: migrate: do not migrate HugeTLB page whose refcount is one X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=71a64f618be9594cd0645105c0989855c0f86d90;p=linux.git mm: migrate: do not migrate HugeTLB page whose refcount is one All pages isolated for the migration have an elevated reference count and therefore seeing a reference count equal to 1 means that the last user of the page has dropped the reference and the page has became unused and there doesn't make much sense to migrate it anymore. This has been done for regular pages and this patch does the same for hugetlb pages. Although the likelihood of the race is rather small for hugetlb pages it makes sense the two code paths in sync. Link: https://lkml.kernel.org/r/20210115124942.46403-2-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Mike Kravetz Acked-by: Yang Shi Acked-by: Michal Hocko Reviewed-by: David Hildenbrand Reviewed-by: Oscar Salvador Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/migrate.c b/mm/migrate.c index c0efe921bca5c..20ca887ea7694 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1280,6 +1280,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, return -ENOSYS; } + if (page_count(hpage) == 1) { + /* page was freed from under us. So we are done. */ + putback_active_hugepage(hpage); + return MIGRATEPAGE_SUCCESS; + } + new_hpage = get_new_page(hpage, private); if (!new_hpage) return -ENOMEM;