linux-kernel - Re: [PATCH 2/2] mm/migrate_device: further convert migrate_device

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Date: Thu, 15 Feb 2024 11:58:54 +1100
From: Alistair Popple <apopple@...dia.com>
To: Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 akpm@...ux-foundation.org, willy@...radead.org
Subject: Re: [PATCH 2/2] mm/migrate_device: further convert
 migrate_device_finalize() to folios


Sidhartha Kumar <sidhartha.kumar@...cle.com> writes:

> On 2/14/24 2:45 PM, Alistair Popple wrote:
>> Sidhartha Kumar <sidhartha.kumar@...cle.com> writes:
>> 
>>> Use folio api functions from the already defined src and dst folio
>>> variables.
>>>
>>> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
>>> ---
>>>   mm/migrate_device.c | 14 +++++++-------
>>>   1 file changed, 7 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
>>> index 9152a329b0a68..a48d5cdb28553 100644
>>> --- a/mm/migrate_device.c
>>> +++ b/mm/migrate_device.c
>>> @@ -843,17 +843,17 @@ void migrate_device_finalize(unsigned long *src_pfns,
>>>   		remove_migration_ptes(src, dst, false);
>>>   		folio_unlock(src);
>>>   -		if (is_zone_device_page(page))
>>> -			put_page(page);
>>> +		if (folio_is_zone_device(src))
>>> +			folio_put(src);
>>>   		else
>>> -			putback_lru_page(page);
>>> +			folio_putback_lru(src);
>>>     		if (newpage != page) {
>>> -			unlock_page(newpage);
>>> -			if (is_zone_device_page(newpage))
>>> -				put_page(newpage);
>> Defining migrate_pfn_to_folio() would also allow the removal of the
>> newpage and page variables entirely which I think would make this
>> clearer.
>> As an aside is there any motivation for making these changes other
>> than
>> as a general cleanup? I ask only because I have been looking at allowing
>> device pages with order > 0 so have some of these clean-ups in a local
>> tree as they're a pre-requisite for that.
>>   - Alistair
>> 
>
> Hello,
>
> The motivation is just general cleanup. In folio-compat.c I saw that
> putback_lru_page() does not have much users left so I could convert
> them and then just get rid of putback_lru_page(). Should I still
> continue with a v2 that will include defining a migrate_pfn_to_folio()
> or wait for your clean-ups?

No, don't wait for mine. Please continue with defining
migrate_pfn_to_folio() for v2, I was just curious in case you had some
larger goal in mind.

Thanks.

 - Alistair

> Thanks,
> Sid
>
>>> +			folio_unlock(dst);
>>> +			if (folio_is_zone_device(dst))
>>> +				folio_put(dst);
>>>   			else
>>> -				putback_lru_page(newpage);
>>> +				folio_putback_lru(dst);
>>>   		}
>>>   	}
>>>   }
>>