linux.git/kernel/liveupdate/luo_session.c, branch v6.19.12

liveupdate: luo_session: add ioctls for file preservation

2025-11-27T22:24:39+00:00

Introducing the userspace interface and internal logic required to manage
the lifecycle of file descriptors within a session.  Previously, a session
was merely a container; this change makes it a functional management unit.

The following capabilities are added:

A new set of ioctl commands are added, which operate on the file
descriptor returned by CREATE_SESSION. This allows userspace to:
- LIVEUPDATE_SESSION_PRESERVE_FD: Add a file descriptor to a session
  to be preserved across the live update.
- LIVEUPDATE_SESSION_RETRIEVE_FD: Retrieve a preserved file in the
  new kernel using its unique token.
- LIVEUPDATE_SESSION_FINISH: finish session

The session's .release handler is enhanced to be state-aware.  When a
session's file descriptor is closed, it correctly unpreserves the session
based on its current state before freeing all associated file resources.

Link: https://lkml.kernel.org/r/20251125165850.3389713-8-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav 
Reviewed-by: Mike Rapoport (Microsoft) 
Tested-by: David Matlack 
Cc: Aleksander Lobakin 
Cc: Alexander Graf 
Cc: Alice Ryhl 
Cc: Andriy Shevchenko 
Cc: anish kumar 
Cc: Anna Schumaker 
Cc: Bartosz Golaszewski 
Cc: Bjorn Helgaas 
Cc: Borislav Betkov 
Cc: Chanwoo Choi 
Cc: Chen Ridong 
Cc: Chris Li 
Cc: Christian Brauner 
Cc: Daniel Wagner 
Cc: Danilo Krummrich 
Cc: Dan Williams 
Cc: David Hildenbrand 
Cc: David Jeffery 
Cc: David Rientjes 
Cc: Greg Kroah-Hartman 
Cc: Guixin Liu 
Cc: "H. Peter Anvin" 
Cc: Hugh Dickins 
Cc: Ilpo Järvinen 
Cc: Ingo Molnar 
Cc: Ira Weiny 
Cc: Jann Horn 
Cc: Jason Gunthorpe 
Cc: Jens Axboe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: Johannes Weiner 
Cc: Jonathan Corbet 
Cc: Lennart Poettering 
Cc: Leon Romanovsky 
Cc: Leon Romanovsky 
Cc: Lukas Wunner 
Cc: Marc Rutland 
Cc: Masahiro Yamada 
Cc: Matthew Maurer 
Cc: Miguel Ojeda 
Cc: Myugnjoo Ham 
Cc: Parav Pandit 
Cc: Pratyush Yadav 
Cc: Randy Dunlap 
Cc: Roman Gushchin 
Cc: Saeed Mahameed 
Cc: Samiullah Khawaja 
Cc: Song Liu 
Cc: Steven Rostedt 
Cc: Stuart Hayes 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Weißschuh 
Cc: Vincent Guittot 
Cc: William Tu 
Cc: Yoann Congal 
Cc: Zhu Yanjun 
Cc: Zijun Hu 
Signed-off-by: Andrew Morton

liveupdate: luo_session: add sessions support

2025-11-27T22:24:38+00:00

Introduce concept of "Live Update Sessions" within the LUO framework.  LUO
sessions provide a mechanism to group and manage `struct file *` instances
(representing file descriptors) that need to be preserved across a
kexec-based live update.

Each session is identified by a unique name and acts as a container for
file objects whose state is critical to a userspace workload, such as a
virtual machine or a high-performance database, aiming to maintain their
functionality across a kernel transition.

This groundwork establishes the framework for preserving file-backed state
across kernel updates, with the actual file data preservation mechanisms
to be implemented in subsequent patches.

[dan.carpenter@linaro.org: fix use after free in luo_session_deserialize()]
  Link: https://lkml.kernel.org/r/c5dd637d7eed3a3be48c5e9fedb881596a3b1f5a.1764163896.git.dan.carpenter@linaro.org
Link: https://lkml.kernel.org/r/20251125165850.3389713-5-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Signed-off-by: Dan Carpenter 
Reviewed-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav 
Tested-by: David Matlack 
Cc: Aleksander Lobakin 
Cc: Alexander Graf 
Cc: Alice Ryhl 
Cc: Andriy Shevchenko 
Cc: anish kumar 
Cc: Anna Schumaker 
Cc: Bartosz Golaszewski 
Cc: Bjorn Helgaas 
Cc: Borislav Betkov 
Cc: Chanwoo Choi 
Cc: Chen Ridong 
Cc: Chris Li 
Cc: Christian Brauner 
Cc: Daniel Wagner 
Cc: Danilo Krummrich 
Cc: Dan Williams 
Cc: David Hildenbrand 
Cc: David Jeffery 
Cc: David Rientjes 
Cc: Greg Kroah-Hartman 
Cc: Guixin Liu 
Cc: "H. Peter Anvin" 
Cc: Hugh Dickins 
Cc: Ilpo Järvinen 
Cc: Ingo Molnar 
Cc: Ira Weiny 
Cc: Jann Horn 
Cc: Jason Gunthorpe 
Cc: Jens Axboe 
Cc: Joanthan Cameron 
Cc: Joel Granados 
Cc: Johannes Weiner 
Cc: Jonathan Corbet 
Cc: Lennart Poettering 
Cc: Leon Romanovsky 
Cc: Leon Romanovsky 
Cc: Lukas Wunner 
Cc: Marc Rutland 
Cc: Masahiro Yamada 
Cc: Matthew Maurer 
Cc: Miguel Ojeda 
Cc: Myugnjoo Ham 
Cc: Parav Pandit 
Cc: Pratyush Yadav 
Cc: Randy Dunlap 
Cc: Roman Gushchin 
Cc: Saeed Mahameed 
Cc: Samiullah Khawaja 
Cc: Song Liu 
Cc: Steven Rostedt 
Cc: Stuart Hayes 
Cc: Tejun Heo 
Cc: Thomas Gleinxer 
Cc: Thomas Weißschuh 
Cc: Vincent Guittot 
Cc: William Tu 
Cc: Yoann Congal 
Cc: Zhu Yanjun 
Cc: Zijun Hu 
Signed-off-by: Andrew Morton