linux-stable.git/kernel/liveupdate, branch master

Merge tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-04-19T15:01:17+00:00

Pull more MM updates from Andrew Morton:

 - "Eliminate Dying Memory Cgroup" (Qi Zheng and Muchun Song)

   Address the longstanding "dying memcg problem". A situation wherein a
   no-longer-used memory control group will hang around for an extended
   period pointlessly consuming memory

 - "fix unexpected type conversions and potential overflows" (Qi Zheng)

   Fix a couple of potential 32-bit/64-bit issues which were identified
   during review of the "Eliminate Dying Memory Cgroup" series

 - "kho: history: track previous kernel version and kexec boot count"
   (Breno Leitao)

   Use Kexec Handover (KHO) to pass the previous kernel's version string
   and the number of kexec reboots since the last cold boot to the next
   kernel, and print it at boot time

 - "liveupdate: prevent double preservation" (Pasha Tatashin)

   Teach LUO to avoid managing the same file across different active
   sessions

 - "liveupdate: Fix module unloading and unregister API" (Pasha
   Tatashin)

   Address an issue with how LUO handles module reference counting and
   unregistration during module unloading

 - "zswap pool per-CPU acomp_ctx simplifications" (Kanchana Sridhar)

   Simplify and clean up the zswap crypto compression handling and
   improve the lifecycle management of zswap pool's per-CPU acomp_ctx
   resources

 - "mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit race"
   (SeongJae Park)

   Address unlikely but possible leaks and deadlocks in damon_call() and
   damon_walk()

 - "mm/damon/core: validate damos_quota_goal->nid" (SeongJae Park)

   Fix a couple of root-only wild pointer dereferences

 - "Docs/admin-guide/mm/damon: warn commit_inputs vs other params race"
   (SeongJae Park)

   Update the DAMON documentation to warn operators about potential
   races which can occur if the commit_inputs parameter is altered at
   the wrong time

 - "Minor hmm_test fixes and cleanups" (Alistair Popple)

   Bugfixes and a cleanup for the HMM kernel selftests

 - "Modify memfd_luo code" (Chenghao Duan)

   Cleanups, simplifications and speedups to the memfd_lou code

 - "mm, kvm: allow uffd support in guest_memfd" (Mike Rapoport)

   Support for userfaultfd in guest_memfd

 - "selftests/mm: skip several tests when thp is not available" (Chunyu
   Hu)

   Fix several issues in the selftests code which were causing breakage
   when the tests were run on CONFIG_THP=n kernels

 - "mm/mprotect: micro-optimization work" (Pedro Falcato)

   A couple of nice speedups for mprotect()

 - "MAINTAINERS: update KHO and LIVE UPDATE entries" (Pratyush Yadav)

   Document upcoming changes in the maintenance of KHO, LUO, memfd_luo,
   kexec, crash, kdump and probably other kexec-based things - they are
   being moved out of mm.git and into a new git tree

* tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (121 commits)
  MAINTAINERS: add page cache reviewer
  mm/vmscan: avoid false-positive -Wuninitialized warning
  MAINTAINERS: update Dave's kdump reviewer email address
  MAINTAINERS: drop include/linux/liveupdate from LIVE UPDATE
  MAINTAINERS: drop include/linux/kho/abi/ from KHO
  MAINTAINERS: update KHO and LIVE UPDATE maintainers
  MAINTAINERS: update kexec/kdump maintainers entries
  mm/migrate_device: remove dead migration entry check in migrate_vma_collect_huge_pmd()
  selftests: mm: skip charge_reserved_hugetlb without killall
  userfaultfd: allow registration of ranges below mmap_min_addr
  mm/vmstat: fix vmstat_shepherd double-scheduling vmstat_update
  mm/hugetlb: fix early boot crash on parameters without '=' separator
  zram: reject unrecognized type= values in recompress_store()
  docs: proc: document ProtectionKey in smaps
  mm/mprotect: special-case small folios when applying permissions
  mm/mprotect: move softleaf code out of the main function
  mm: remove '!root_reclaim' checking in should_abort_scan()
  mm/sparse: fix comment for section map alignment
  mm/page_io: use sio->len for PSWPIN accounting in sio_read_complete()
  selftests/mm: transhuge_stress: skip the test when thp not available
  ...

liveupdate: defer file handler module refcounting to active sessions

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

Stop pinning modules indefinitely upon file handler registration. 
Instead, dynamically increment the module reference count only when a live
update session actively uses the file handler (e.g., during preservation
or deserialization), and release it when the session ends.

This allows modules providing live update handlers to be gracefully
unloaded when no live update is in progress.

Link: https://lore.kernel.org/20260327033335.696621-11-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: 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: remove liveupdate_test_unregister()

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

Now that file handler unregistration automatically unregisters all
associated file handlers (FLBs), the liveupdate_test_unregister() function
is no longer needed.  Remove it along with its usages and declarations.

Link: https://lore.kernel.org/20260327033335.696621-9-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: protect file handler list with rwsem

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

Because liveupdate file handlers will no longer hold a module reference
when registered, we must ensure that the access to the handler list is
protected against concurrent module unloading.

Utilize the global luo_register_rwlock to protect the global registry of
file handlers.  Read locks are taken during list traversals in
luo_preserve_file() and luo_file_deserialize().  Write locks are taken
during registration and unregistration.

Link: https://lore.kernel.org/20260327033335.696621-4-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