Re: [PATCH] mm/gup: stop leaking pinned pages in low memory conditions

David Hildenbrand
2024-10-17T17:10:55Z

On 17.10.24 19:06, John Hubbard wrote:
> On 10/17/24 1:53 AM, David Hildenbrand wrote:
>> On 17.10.24 10:51, David Hildenbrand wrote:
>>> On 16.10.24 22:22, John Hubbard wrote:
> ...
>> And staring at memfd_pin_folios(), don't we have the same issue there if
>> check_and_migrate_movable_folios() fails?
>
> Yes, it looks very clearly like the exact same bug, in a different location.
> This complicated return code is the gift that keeps on giving. Although
> likely people are just copying the pattern, which had the problem.
>
>
>>
>> diff --git a/mm/gup.c b/mm/gup.c
>> index a82890b46a36..f79974d38608 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -3708,12 +3708,10 @@ long memfd_pin_folios(struct file *memfd, loff_t
>> start, loff_t end,
>>                 ret = check_and_migrate_movable_folios(nr_folios, folios);
>>         } while (ret == -EAGAIN);
>>
>> -       memalloc_pin_restore(flags);
>> -       return ret ? ret : nr_folios;
>>  err:
>>         memalloc_pin_restore(flags);
>> -       unpin_folios(folios, nr_folios);
>> -
>> -       return ret;
>> +       if (ret)
>> +               unpin_folios(folios, nr_folios);
>> +       return ret ? ret : nr_folios;
>
> That looks correct. I can send this out with the other patch as a tiny
> 2-patch series since they are related. Would you prefer to appear
> as a Signed-off-by, or a Suggested-by, or "other"? :)

Suggested-by: please :)

--
Cheers,

David / dhildenb