linux-kernel - Re: [PATCH 2/4] mm/huge_memory: move to next folio after folio

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Message-ID: <30335873-106F-4154-B035-4310089849E4@nvidia.com>
Date: Thu, 07 Aug 2025 13:04:34 -0400
From: Zi Yan <ziy@...dia.com>
To: Wei Yang <richard.weiyang@...il.com>
Cc: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Vlastimil Babka <vbabka@...e.cz>,
 Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Shuah Khan <shuah@...nel.org>,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/4] mm/huge_memory: move to next folio after
 folio_split() succeeds.

On 7 Aug 2025, at 4:45, Wei Yang wrote:

> On Tue, Aug 05, 2025 at 10:20:43PM -0400, Zi Yan wrote:
>> Current behavior is to move to next PAGE_SIZE and split, but that makes it
>> hard to check after-split folio orders. This is a preparation patch to
>> allow more precise split_huge_page_test check in an upcoming commit.
>>
>> split_folio_to_order() part is not changed, since split_pte_mapped_thp test
>> relies on its current behavior.
>>
>> Signed-off-by: Zi Yan <ziy@...dia.com>
>> ---
>> mm/huge_memory.c | 18 +++++++++++-------
>> 1 file changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 8a11c2d402d4..b2ce8ac0c5a9 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -4341,6 +4341,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>> 		struct folio *folio;
>> 		struct address_space *mapping;
>> 		unsigned int target_order = new_order;
>> +		long nr_pages;
>>
>> 		if (!vma)
>> 			break;
>> @@ -4358,6 +4359,8 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>> 		if (!is_transparent_hugepage(folio))
>> 			goto next;
>>
>> +		nr_pages = folio_nr_pages(folio);
>> +
>
> Could be folio_large_nr_pages()?

Sure.
>
>> 		if (!folio_test_anon(folio)) {
>> 			mapping = folio->mapping;
>> 			target_order = max(new_order,
>> @@ -4385,15 +4388,16 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>> 		if (!folio_test_anon(folio) && folio->mapping != mapping)
>> 			goto unlock;
>>
>> -		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;
>> +			}
>> 		}
>>
>> unlock:
>> @@ -4438,8 +4442,8 @@ static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
>> 	if (IS_ERR(candidate))
>> 		goto out;
>>
>> -	pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
>> -		 file_path, off_start, off_end);
>> +	pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx], new_order %u in_folio_offset %ld\n",
>> +		 file_path, off_start, off_end, new_order, in_folio_offset);
>>
>
> How about move this part into patch 1?

Sure. I missed it. Thanks.
>
>> 	mapping = candidate->f_mapping;
>> 	min_order = mapping_min_folio_order(mapping);
>> -- 
>> 2.47.2
>>
>
> -- 
> Wei Yang
> Help you, Help me


--
Best Regards,
Yan, Zi