Re: [PATCH 2/4] mm/huge_memory: move to next folio after folio_split() succeeds.

[Zi Yan <ziy@nvidia.com>]

On 7 Aug 2025, at 23:15, Wei Yang wrote:

> On Thu, Aug 07, 2025 at 01:05:09PM -0400, Zi Yan wrote:
>> On 7 Aug 2025, at 4:55, Wei Yang wrote:
>>
>>> On Tue, Aug 05, 2025 at 10:20:43PM -0400, Zi Yan wrote:
>>> [...]
>>>>
>>>> -		if (in_folio_offset < 0 ||
>>>> -		    in_folio_offset >= folio_nr_pages(folio)) {
>>>> +		if (in_folio_offset < 0 || in_folio_offset >= nr_pages) {
>>>> 			if (!split_folio_to_order(folio, target_order))
>>>> 				split++;
>>>> 		} else {
>>>> -			struct page *split_at = folio_page(folio,
>>>> -							   in_folio_offset);
>>>> -			if (!folio_split(folio, target_order, split_at, NULL))
>>>> +			struct page *split_at =
>>>> +				folio_page(folio, in_folio_offset);
>>>> +			if (!folio_split(folio, target_order, split_at, NULL)) {
>>>> 				split++;
>>>> +				addr += PAGE_SIZE * nr_pages;
>>>> +			}
>>>
>>> Are we sure addr points to the folio start?
>>
>> David pointed it out. Will use addr += PAGE_SIZE * (nr_pages - 1).
>>
>
> No, let me be more clear. I am talking about the addr in next iteration. I am
> talking about the addr in this round.
>
> For an addr in the middle of 2M, we still could get the large folio if my
> understanding is correct.  Then (addr + whole folio size) seems wrong.
>
>              addr
> 	     |
> 	     v
>       +-------------------+
>       |                   |
>       +-------------------+
>
> Not sure this would be the case.

Got it. addr should be aligned up to PAGE_SIZE * nr_pages to get to the next
folio. Thanks.

--
Best Regards,
Yan, Zi