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

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Message-ID: <20250806022045.342824-3-ziy@nvidia.com>
Date: Tue,  5 Aug 2025 22:20:43 -0400
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>,
	linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Zi Yan <ziy@...dia.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: [PATCH 2/4] mm/huge_memory: move to next folio after folio_split() succeeds.

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);
+
 		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);
 
 	mapping = candidate->f_mapping;
 	min_order = mapping_min_folio_order(mapping);
-- 
2.47.2