linux.git/kernel/liveupdate, branch master

liveupdate: Remove limit on the number of files per session

2026-06-03T18:15:46+00:00

To remove the fixed limit on the number of preserved files per session,
transition the file metadata serialization from a single contiguous
memory block to a chain of linked blocks.

Acked-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav (Google) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-11-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: Remove limit on the number of sessions

2026-06-03T18:15:46+00:00

Currently, the number of LUO sessions is limited by a fixed number of
pre-allocated pages for serialization (16 pages, allowing for ~819
sessions).

This limitation is problematic if LUO is used to support things such as
systemd file descriptor store, and would be used not just as VM memory
but to save other states on the machine.

Remove this limit by transitioning to a linked-block approach for
session metadata serialization. Instead of a single contiguous block,
session metadata is now stored in a chain of 16-page blocks. Each block
starts with a header containing the physical address of the next block
and the number of session entries in the current block.

Acked-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav (Google) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-10-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: defer session block allocation and physical address setting

2026-06-03T18:15:46+00:00

Currently, luo_session_setup_outgoing() allocates the session block and
sets its physical address in the header immediately. With upcoming
dynamic block-based session management, this makes the first block
different from the rest. Move the allocation to where it is first needed.

Acked-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav (Google) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-9-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

kho: add support for linked-block serialization

2026-06-03T18:15:46+00:00

Introduce a linked-block serialization mechanism for state handover.

Previously, LUO used contiguous memory blocks for serializing sessions
and files, which imposed limits on the total number of items that could
be preserved across a live update.

This commit adds the infrastructure for a more flexible, block-based
approach where serialized data is stored in a chain of linked blocks.
This is a generic KHO serialization block infrastructure that can be
used by multiple subsystems.

Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-8-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: Extract luo_session_deserialize_one helper

2026-06-03T18:15:46+00:00

Extract the logic for deserializing single entries for sessions into
separate helper functions. In preparation to a linked-block
serialization for sessions.

This is a pure code movement, no other changes intended.

Acked-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav (Google) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-7-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: Extract luo_file_deserialize_one helper

2026-06-03T18:15:46+00:00

Extract the logic for deserializing single entries for files into
separate helper functions. In preparation to a linked-block
serialization for files.

This is a pure code movement, no other changes intended.

Acked-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav (Google) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-6-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: register luo_ser as KHO subtree

2026-06-03T18:15:45+00:00

Entirely remove the LUO FDT wrapper since the FDT only carries the
compatible string and the pointer to the centralized struct luo_ser.
Instead, register the struct luo_ser via the KHO raw subtree
API, placing the compatibility string inside the structure itself.

Acked-by: Mike Rapoport (Microsoft) 
Reviewed-by: Pratyush Yadav (Google) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-5-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: centralize state management into struct luo_ser

2026-06-03T18:15:45+00:00

Transition the LUO to ABI v2, which centralizes state management into a
single struct luo_ser header.

Previously, LUO state was spread across multiple FDT properties and
subnodes. ABI v2 simplifies this by placing all core state, including
the liveupdate number and physical addresses for sessions and FLB
headers into a centralized struct luo_ser.

Note that this change introduces a semantic difference: the sessions
and FLB serialization formats are no longer completely independent of
the core LUO. Their metadata (such as physical addresses for sessions
and FLB headers) is now coupled to and managed via the centralized
struct luo_ser.

Reviewed-by: Pratyush Yadav (Google) 
Acked-by: Mike Rapoport (Microsoft) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-4-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: avoid mixing cleanup guards with goto in luo_session_retrieve_fd

2026-06-03T18:15:45+00:00

Refactoring luo_session_retrieve_fd() to avoid mixing automated
cleanup-style guards with goto-based resource release, which is not
recommended under the Linux kernel coding style.

Reviewed-by: Pratyush Yadav (Google) 
Acked-by: Mike Rapoport (Microsoft) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-3-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: change file_set->count type to u64 for type safety

2026-06-03T18:15:45+00:00

This improves type safety and aligns the in-memory file_set->count with
the serialized count type. It avoids potential truncation or sign
conversion mismatch issues.

Reviewed-by: Pratyush Yadav (Google) 
Acked-by: Mike Rapoport (Microsoft) 
Signed-off-by: Pasha Tatashin 
Link: https://patch.msgid.link/20260603154402.468928-2-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft)