On 2025/3/1 01:49, 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@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/28546fb4-5210-bf75-16d6-43e1f8646080@xxxxxxxxxx/
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: Shivank Garg <shivankg@xxxxxxx>
LGTM. Thanks.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
---
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;
