[PATCH 2/2] mm/memfd_luo: document preservation of file seals

David Carlier
2026-04-23T12:56:58Z

Commit 8a552d68a86e ("mm: memfd_luo: preserve file seals") started
preserving file seals across live update and restoring them via
memfd_add_seals() on retrieve, but the DOC header was not updated and
still listed seals under "Non-Preserved Properties" as being unsealed
on restore.

Move the Seals entry to the "Preserved Properties" section and describe
the actual behavior, including the MEMFD_LUO_ALL_SEALS restriction that
both preserve and retrieve enforce.

Fixes: 8a552d68a86e ("mm: memfd_luo: preserve file seals")
Signed-off-by: David Carlier <devnexen@gmail.com>
---
mm/memfd_luo.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index f41d11053b7d..c5250f68c096 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -50,6 +50,11 @@
* memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property
* is maintained.
*
+ * Seals
+ * File seals set on the memfd are preserved and re-applied on restore.
+ * Only seals known to this LUO version (see ``MEMFD_LUO_ALL_SEALS``) may
+ * be present; preservation fails with ``-EOPNOTSUPP`` otherwise.
+ *
* Non-Preserved Properties
* ========================
*
@@ -61,10 +66,6 @@
* A memfd can be created with the ``MFD_CLOEXEC`` flag that sets the
* ``FD_CLOEXEC`` on the file. This flag is not preserved and must be set
* again after restore via ``fcntl()``.
- *
- * Seals
- * File seals are not preserved. The file is unsealed on restore and if
- * needed, must be sealed again via ``fcntl()``.
*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
--
2.53.0