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

__split_huge_pud_locked() updates the file/shmem RSS counter after
dropping the PUD 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/20260526101355.1984244-1-yintirui@huawei.com
Fixes: dbe54153296d ("mm/huge_memory: add vmf_insert_folio_pud()")
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: Alistair Popple <apopple@nvidia.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: 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 970e077019b75a4ad140c6ac16d993544fc85298..1f78b73a0ca4eb907394f6ccae5bf7ff0e1a50ef 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3015,9 +3015,9 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
        if (!folio_test_referenced(folio) && pud_young(old_pud))
                folio_set_referenced(folio);
        folio_remove_rmap_pud(folio, page, vma);
-       folio_put(folio);
        add_mm_counter(vma->vm_mm, mm_counter_file(folio),
                -HPAGE_PUD_NR);
+       folio_put(folio);
 }
 
 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,