mm/huge_memory: update file PMD counter before folio_put()

__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>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1f78b73a0ca4eb907394f6ccae5bf7ff0e1a50ef..653f2dc034036e7593b9b50ec191928e63c53189 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3133,7 +3133,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
                        if (!folio_test_referenced(folio) && pmd_young(old_pmd))
                                folio_set_referenced(folio);
                        folio_remove_rmap_pmd(folio, page, vma);
+                       add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR);
                        folio_put(folio);
+                       return;
                }
                add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR);
                return;