On 2022/3/18 15:08, Feng Tang wrote:
>> 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 :).
>
Oh, what a coincidence! :)
> 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>
Many thanks for your test and comment!
>
> 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
>
> .
>
