linux.git/kernel/liveupdate/luo_flb.c, branch master

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: Reference count incoming FLB data

2026-05-31T23:31:38+00:00

Increment the incoming FLB refcount in liveupdate_flb_get_incoming() so
that the FLB structure cannot be freed while the caller is actively using
it. Add an additional liveupdate_flb_put_incoming() function so the
caller can explicitly indicate when it is done using the FLB data.

During a Live Update, a subsystem might need to hold onto the incoming
File-Lifecycle-Bound (FLB) data for an extended period, such as during
device enumeration. Incrementing the reference count guarantees that the
data remains valid and accessible until the subsystem releases it,
preventing future use-after-free bugs.

Fixes: cab056f2aae7 ("liveupdate: luo_flb: introduce File-Lifecycle-Bound global state")
Signed-off-by: David Matlack 
Reviewed-by: Samiullah Khawaja 
Reviewed-by: Pasha Tatashin 
Link: https://lore.kernel.org/r/20260423174032.3140399-3-dmatlack@google.com
Signed-off-by: Pasha Tatashin 
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: Use refcount_t for FLB reference counts

2026-05-31T23:31:38+00:00

Use refcount_t instead of a raw integer to keep track of references on
incoming and outgoing FLBs. Using refcount_t provides protection from
overflow, underflow, and other issues.

Fixes: cab056f2aae7 ("liveupdate: luo_flb: introduce File-Lifecycle-Bound global state")
Signed-off-by: David Matlack 
Reviewed-by: Samiullah Khawaja 
Reviewed-by: Pasha Tatashin 
Link: https://lore.kernel.org/r/20260423174032.3140399-2-dmatlack@google.com
Signed-off-by: Pasha Tatashin 
Signed-off-by: Mike Rapoport (Microsoft)

liveupdate: make unregister functions return void

2026-04-18T07:10:50+00:00

Change liveupdate_unregister_file_handler and liveupdate_unregister_flb to
return void instead of an error code.  This follows the design principle
that unregistration during module unload should not fail, as the unload
cannot be stopped at that point.

Link: https://lore.kernel.org/20260327033335.696621-10-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

liveupdate: auto unregister FLBs on file handler unregistration

2026-04-18T07:10:50+00:00

To ensure that unregistration is always successful and doesn't leave
dangling resources, introduce auto-unregistration of FLBs: when a file
handler is unregistered, all FLBs associated with it are automatically
unregistered.

Introduce a new helper luo_flb_unregister_all() which unregisters all FLBs
linked to the given file handler.

Link: https://lore.kernel.org/20260327033335.696621-8-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

liveupdate: remove luo_session_quiesce()

2026-04-18T07:10:50+00:00

Now that FLB module references are handled dynamically during active
sessions, we can safely remove the luo_session_quiesce() and
luo_session_resume() mechanism.

Link: https://lore.kernel.org/20260327033335.696621-7-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

liveupdate: defer FLB module refcounting to active sessions

2026-04-18T07:10:50+00:00

Stop pinning modules indefinitely upon FLB registration.  Instead,
dynamically take a module reference when the FLB is actively used in a
session (e.g., during preserve and retrieve) and release it when the
session concludes.

This allows modules providing FLB operations to be cleanly unloaded when
not in active use by the live update orchestrator.

Link: https://lore.kernel.org/20260327033335.696621-6-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Samiullah Khawaja 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Signed-off-by: Andrew Morton

liveupdate: protect FLB lists with luo_register_rwlock

2026-04-18T07:10:49+00:00

Because liveupdate FLB objects will soon drop their persistent module
references when registered, list traversals must be protected against
concurrent module unloading.

To provide this protection, utilize the global luo_register_rwlock.  It
protects the global registry of FLBs and the handler's specific list of
FLB dependencies.

Read locks are used during concurrent list traversals (e.g., during
preservation and serialization).  Write locks are taken during
registration and unregistration.

Link: https://lore.kernel.org/20260327033335.696621-5-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav (Google) 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

liveupdate: synchronize lazy initialization of FLB private state

2026-04-18T07:10:49+00:00

The luo_flb_get_private() function, which is responsible for lazily
initializing the private state of FLB objects, can be called concurrently
from multiple threads.  This creates a data race on the 'initialized' flag
and can lead to multiple executions of mutex_init() and INIT_LIST_HEAD()
on the same memory.

Introduce a static spinlock (luo_flb_init_lock) local to the function to
synchronize the initialization path.  Use smp_load_acquire() and
smp_store_release() for memory ordering between the fast path and the slow
path.

Link: https://lore.kernel.org/20260327033335.696621-3-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin 
Reviewed-by: Pratyush Yadav 
Cc: David Matlack 
Cc: Mike Rapoport 
Cc: Samiullah Khawaja 
Signed-off-by: Andrew Morton

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using

    git grep -l '\