Re: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap read fails

David Hildenbrand
2022-04-20T07:07:56Z

On 20.04.22 08:15, Miaohe Lin wrote:
> On 2022/4/20 8:25, Alistair Popple wrote:
>> Miaohe Lin <linmiaohe@huawei.com> writes:
>>
>>> On 2022/4/19 15:53, Alistair Popple wrote:
>>>> Also in madvise_free_pte_range() you could just remove the swap entry as it's no
>>>> longer needed.
>>>>
>>>
>>> This swap entry will be removed in madvise_dontneed_single_vma().
>>> And in madvise_free_pte_range(), we may need to keep it as same as
>>> hwpoison entry. Or am I supposed to remove it even if hwpoison entry
>>> is reused later?
>>
>> Why would we need to keep it for MADV_FREE though? It only works on private
>> anonymous memory, and once the MADV_FREE operation has succeeded callers can
>> expect they might get zero-fill pages if accessing the memory again. Therefore
>> it should be safe to delete the entry. I think that applies equally to a
>> hwpoison entry too - there's no reason to kill the process if it has called
>> MADV_FREE on the range.
>
> I tend to agree. We can drop the swapin error entry and hwpoison entry when MADV_FREE
> is called. Should I squash these into the current patch or a separate one is preferred?
>

That should go into a separate patch.

--
Thanks,

David / dhildenb