> In -ENOMEM case, there might be some subpages of fail-to-migrate THPs
> left in thp_split_pages list. We should move them back to migration
> list so that they could be put back to the right list by the caller
> otherwise the page refcnt will be leaked here. Also adjust nr_failed
> and nr_thp_failed accordingly to make vm events account more accurate.
We just met a real world case for this when checking a malloc-oom
issue and our fix is similar with yours :).
So I think you can remove the 'potential' from the patch subject.
Feel free to add
Tested-by: Feng Tang <feng.tang@xxxxxxxxx>
Reviewed-by: Feng Tang <feng.tang@xxxxxxxxx>
Thanks,
Feng
> Fixes: b5bade978e9b ("mm: migrate: fix the return value of migrate_pages()")
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
> Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
> mm/migrate.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 63a87ef0996f..97dfd1f4870d 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1438,6 +1438,14 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> }
>
> nr_failed_pages += nr_subpages;
> + /*
> + * There might be some subpages of fail-to-migrate THPs
> + * left in thp_split_pages list. Move them back to migration
> + * list so that they could be put back to the right list by
> + * the caller otherwise the page refcnt will be leaked.
> + */
> + list_splice_init(&thp_split_pages, from);
> + nr_thp_failed += thp_retry;
> goto out;
> case -EAGAIN:
> if (is_thp)
> --
> 2.23.0
