Re: [PATCH 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one

[Yang Shi]

On Sun, Jan 3, 2021 at 11:01 PM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
>
> If the refcount is one when it is migrated, it means that the page
> was freed from under us. So we are done and do not need to migrate.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
>  mm/migrate.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 4385f2fb5d18..a6631c4eb6a6 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1279,6 +1279,12 @@ 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;
> +       }
> +

Acked-by: Yang Shi <shy828301@xxxxxxxxx>

>         new_hpage = get_new_page(hpage, private);
>         if (!new_hpage)
>                 return -ENOMEM;
> --
> 2.11.0
>
>