On 2022/3/31 16:02, Huang, Ying wrote:
> Miaohe Lin <linmiaohe@xxxxxxxxxx> writes:
>
>> On 2022/3/31 14:37, Huang, Ying wrote:
>>> Muchun Song <songmuchun@xxxxxxxxxxxxx> writes:
>>>
>>>> On Tue, Mar 29, 2022 at 9:26 PM Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
>>>>>
>>>>> When folio is file lru, folio_test_swapbacked is guaranteed to be true. So
>>>>> it's unnecessary to check it here again. No functional change intended.
>>>>>
>>>>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>>>>> ---
>>>>> mm/vmscan.c | 3 +--
>>>>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>>>> index 1678802e03e7..7c1a9713bfc9 100644
>>>>> --- a/mm/vmscan.c
>>>>> +++ b/mm/vmscan.c
>>>>> @@ -1434,8 +1434,7 @@ static void folio_check_dirty_writeback(struct folio *folio,
>>>>> * Anonymous pages are not handled by flushers and must be written
>>>>> * from reclaim context. Do not stall reclaim based on them
>>>>> */
>>>>> - if (!folio_is_file_lru(folio) ||
>>>>> - (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
>>>>> + if (!folio_is_file_lru(folio) || folio_test_anon(folio)) {
>>>>
>>>> At least your login is no problem since folio_is_file_lru() is equal to
>>>> !folio_test_swapbacked(). But the new code is not clear to me.
>>>> The old code is easy to understand, e.g. folio_test_anon(folio) &&
>>>> !folio_test_swapbacked(folio) tells us that the anon pages which
>>>> do not need to be swapped should be skipped.
>>>
>>> That is for MADV_FREE pages. The code is introduced in commit
>>> 802a3a92ad7a ("mm: reclaim MADV_FREE pages").
>>>
>>> So I think the original code is better. It's an implementation detail
>>> that folio_is_file_lru() equals !folio_test_swapbacked(). It may be
>>> better to add some comments here for MADV_FREE pages.
>>>
>>
>> Do you tend to drop this patch or adding a comment with the change in this patch or something else?
>
> I suggest to drop the code change and add a comment about MADV_FREE.
Will do. Thanks.
>
> Best Regards,
> Huang, Ying
>
>> Thanks.
>>
>>>> So I'm neutral on the patch.
>>>
>>> Best Regards,
>>> Huang, Ying
>>> .
>>>
> .
>
