[PATCH 5.15.y] mm/huge_memory: update file PMD counter before folio_put()

[Sasha Levin <sashal@kernel.org>]

From: Yin Tirui <yintirui@huawei.com>

[ Upstream commit 8d878059924f12c1bc24556a92ec56add74de3c8 ]

__split_huge_pmd_locked() updates the file/shmem RSS counter after
dropping the PMD mapping's folio reference.  If folio_put() drops the last
reference, mm_counter_file() can later read freed folio state via
folio_test_swapbacked().

Move the counter update before folio_put().

Link: https://lore.kernel.org/20260526101337.1984081-1-yintirui@huawei.com
Fixes: fadae2953072 ("thp: use mm_file_counter to determine update which rss counter")
Signed-off-by: Yin Tirui <yintirui@huawei.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: David Hildenbrand (arm) <david@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chen Jun <chenjun102@huawei.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/huge_memory.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e9c5de967b2c15..934c08de74f42d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1994,7 +1994,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 			if (!PageReferenced(page) && pmd_young(old_pmd))
 				SetPageReferenced(page);
 			page_remove_rmap(page, true);
+			add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
 			put_page(page);
+			return;
 		}
 		add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
 		return;
-- 
2.53.0