linux-kernel - [RFC PATCH 2/3] mm/huge_memory: add kernel-doc for folio_split

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Message-ID: <20251120035953.1115736-3-ziy@nvidia.com>
Date: Wed, 19 Nov 2025 22:59:52 -0500
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	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>,
	Lance Yang <lance.yang@...ux.dev>,
	Miaohe Lin <linmiaohe@...wei.com>,
	Naoya Horiguchi <nao.horiguchi@...il.com>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/3] mm/huge_memory: add kernel-doc for folio_split_supported()

It clarifies that folio_split_supported() does not check folio->mapping and
can dereference it.

Signed-off-by: Zi Yan <ziy@...dia.com>
---
 mm/huge_memory.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index efea42d68157..15e555f1b85d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3688,6 +3688,23 @@ static int __split_unmapped_folio(struct folio *folio, int new_order,
 	return 0;
 }
 
+/**
+ * folio_split_supported() - check if a folio can be split to a given order
+ * @folio: folio to be split
+ * @new_order: the smallest order of the after split folios (since buddy
+ *             allocator like split generates folios with orders from @folio's
+ *             order - 1 to new_order).
+ * @split_type: uniform or non-uniform split
+ * @warns: whether gives warnings or not for the checks in the function
+ *
+ * folio_split_supported() checks if @folio can be split to @new_order using
+ * @split_type method.
+ *
+ * Context: Caller must make sure folio->mapping is not NULL, since the
+ *          function does not check it and can dereference folio->mapping
+ * Return: true - @folio can be split to @new_order, false - @folio cannot be
+ * split
+ */
 bool folio_split_supported(struct folio *folio, unsigned int new_order,
 		enum split_type split_type, bool warns)
 {
-- 
2.51.0