On 28 Feb 2025, at 12:49, Zi Yan wrote:

Pagecache uses multi-index entries for large folio, so does shmem. Only swap cache still stores multiple entries for a single large folio. Commit fc346d0a70a1 ("mm: migrate high-order folios in swap cache correctly") fixed swap cache but got shmem wrong by storing multiple entries for a large shmem folio. Fix it by storing a single entry for a shmem folio.

Fixes: fc346d0a70a1 ("mm: migrate high-order folios in swap cache correctly") Reported-by: Liu Shixin liushixin2@huawei.com Closes: https://lore.kernel.org/all/28546fb4-5210-bf75-16d6-43e1f8646080@huawei.com/ Signed-off-by: Zi Yan ziy@nvidia.com Reviewed-by: Shivank Garg shivankg@amd.com

+Cc:stable

---

mm/migrate.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/migrate.c b/mm/migrate.c index 365c6daa8d1b..2c9669135a38 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -524,7 +524,11 @@ static int __folio_migrate_mapping(struct address_space *mapping, folio_set_swapcache(newfolio); newfolio->private = folio_get_private(folio); }

• entries = nr;
  

• /* shmem uses high-order entry */
  

• if (!folio_test_anon(folio))
  

• 	entries = 1;
  

• else
  

• 	entries = nr;
  

  } else { VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio); entries = 1;

-- 2.47.2

Best Regards, Yan, Zi