mm/memfd_luo: document preservation of file seals

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>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://patch.msgid.link/20260423125648.152113-2-devnexen@gmail.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>

diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index 94ae113f68f675dcd746e912862e46a681b93a79..59de210bee5f9e0e39e0914faa0f6019c2df7fcb 100644 (file)
--- 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