docs: add documentation for memfd preservation via LUO

Add the documentation under the "Preserving file descriptors" section of
LUO's documentation.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Pratyush Yadav <[email protected]>
Co-developed-by: Pasha Tatashin <[email protected]>
Signed-off-by: Pasha Tatashin <[email protected]>
Reviewed-by: Mike Rapoport (Microsoft) <[email protected]>
Tested-by: David Matlack <[email protected]>
Cc: Aleksander Lobakin <[email protected]>
Cc: Alexander Graf <[email protected]>
Cc: Alice Ryhl <[email protected]>
Cc: Andriy Shevchenko <[email protected]>
Cc: anish kumar <[email protected]>
Cc: Anna Schumaker <[email protected]>
Cc: Bartosz Golaszewski <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Borislav Betkov <[email protected]>
Cc: Chanwoo Choi <[email protected]>
Cc: Chen Ridong <[email protected]>
Cc: Chris Li <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Daniel Wagner <[email protected]>
Cc: Danilo Krummrich <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Jeffery <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Guixin Liu <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ilpo Järvinen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ira Weiny <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Joanthan Cameron <[email protected]>
Cc: Joel Granados <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Lennart Poettering <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: Lukas Wunner <[email protected]>
Cc: Marc Rutland <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Matthew Maurer <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Myugnjoo Ham <[email protected]>
Cc: Parav Pandit <[email protected]>
Cc: Pratyush Yadav <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Saeed Mahameed <[email protected]>
Cc: Samiullah Khawaja <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Stuart Hayes <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Thomas Gleinxer <[email protected]>
Cc: Thomas Weißschuh <[email protected]>
Cc: Vincent Guittot <[email protected]>
Cc: William Tu <[email protected]>
Cc: Yoann Congal <[email protected]>
Cc: Zhu Yanjun <[email protected]>
Cc: Zijun Hu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Documentation/core-api/liveupdate.rst

@@ -23,6 +23,13 @@ Live Update Orchestrator ABI
 .. kernel-doc:: include/linux/kho/abi/luo.h
    :doc: Live Update Orchestrator ABI
 
+The following types of file descriptors can be preserved
+
+.. toctree::
+   :maxdepth: 1
+
+   ../mm/memfd_preservation
+
 Public API
 ==========
 .. kernel-doc:: include/linux/liveupdate.h

Documentation/mm/index.rst

@@ -48,6 +48,7 @@ documentation, or deleted if it has served its purpose.
    hugetlbfs_reserv
    ksm
    memory-model
+   memfd_preservation
    mmu_notifier
    multigen_lru
    numa

Documentation/mm/memfd_preservation.rst

@@ -0,0 +1,23 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+==========================
+Memfd Preservation via LUO
+==========================
+
+.. kernel-doc:: mm/memfd_luo.c
+   :doc: Memfd Preservation via LUO
+
+Memfd Preservation ABI
+======================
+
+.. kernel-doc:: include/linux/kho/abi/memfd.h
+   :doc: DOC: memfd Live Update ABI
+
+.. kernel-doc:: include/linux/kho/abi/memfd.h
+   :internal:
+
+See Also
+========
+
+- :doc:`/core-api/liveupdate`
+- :doc:`/core-api/kho/concepts`

MAINTAINERS

@@ -14473,6 +14473,7 @@ R:	Pratyush Yadav <[email protected]>
 L:	[email protected]
 S:	Maintained
 F:	Documentation/core-api/liveupdate.rst
+F:	Documentation/mm/memfd_preservation.rst
 F:	Documentation/userspace-api/liveupdate.rst
 F:	include/linux/liveupdate.h
 F:	include/linux/liveupdate/