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Author SHA1 Message Date
Breno Leitao
9ec9532989 kho: fix error handling in kho_add_subtree() 
Fix two error handling issues in kho_add_subtree(), where it doesn't
handle the error path correctly.

1. If fdt_setprop() fails after the subnode has been created, the
   subnode is not removed. This leaves an incomplete node in the FDT
   (missing "preserved-data" or "blob-size" properties).

2. The fdt_setprop() return value (an FDT error code) is stored
   directly in err and returned to the caller, which expects -errno.

Fix both by storing fdt_setprop() results in fdt_err, jumping to a new
out_del_node label that removes the subnode on failure, and only setting
err = 0 on the success path, otherwise returning -ENOMEM (instead of
FDT_ERR_ errors that would come from fdt_setprop).

No user-visible changes.  This patch fixes error handling in the KHO
(Kexec HandOver) subsystem, which is used to preserve data across kexec
reboots.  The fix only affects a rare failure path during kexec
preparation — specifically when the kernel runs out of space in the
Flattened Device Tree buffer while registering preserved memory regions.

In the unlikely event that this error path was triggered, the old code
would leave a malformed node in the device tree and return an incorrect
error code to the calling subsystem, which could lead to confusing log
messages or incorrect recovery decisions.  With this fix, the incomplete
node is properly cleaned up and the appropriate errno value is propagated,
this error code is not returned to the user.

Link: https://lore.kernel.org/20260410-kho_fix_send-v2-1-1b4debf7ee08@debian.org
Fixes: 3dc92c3114 ("kexec: add Kexec HandOver (KHO) generation helpers")
Signed-off-by: Breno Leitao <leitao@debian.org>
Suggested-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-27 05:54:23 -07:00
Pasha Tatashin
0562b572ce liveupdate: fix return value on session allocation failure 
When session allocation fails during deserialization, the global 'err'
variable was not updated before returning.  This caused subsequent calls
to luo_session_deserialize() to incorrectly report success.

Ensure 'err' is set to the error code from PTR_ERR(session).  This ensures
that an error is correctly returned to userspace when it attempts to open
/dev/liveupdate in the new kernel if deserialization failed.

Link: https://lore.kernel.org/20260415193738.515491-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-27 05:54:23 -07:00
Linus Torvalds
40735a683b mm.git review status for linus..mm-stable 
Everything:
 
 Total patches:       121
 Reviews/patch:       2.11
 Reviewed rate:       90%
 
 Excluding DAMON:
 
 Total patches:       113
 Reviews/patch:       2.25
 Reviewed rate:       96%
 
 - The 33 patch series "Eliminate Dying Memory Cgroup" from Qi Zheng and
   Muchun Song addresses 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.  The [0/N]
   changelog has a good overview of this work.
 
 - The 3 patch series "fix unexpected type conversions and potential
   overflows" from Qi Zheng fixes a couple of potential 32-bit/64-bit
   issues which were identified during review of the "Eliminate Dying
   Memory Cgroup" series.
 
 - The 6 patch series "kho: history: track previous kernel version and
   kexec boot count" from Breno Leitao uses 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 prints it at boot time.
 
 - The 4 patch series "liveupdate: prevent double preservation" from
   Pasha Tatashin teaches LUO to avoid managing the same file across
   different active sessions.
 
 - The 10 patch series "liveupdate: Fix module unloading and unregister
   API" from Pasha Tatashin addresses an issue with how LUO handles module
   reference counting and unregistration during module unloading.
 
 - The 2 patch series "zswap pool per-CPU acomp_ctx simplifications" from
   Kanchana Sridhar simplifies and cleans up the zswap crypto compression
   handling and improves the lifecycle management of zswap pool's per-CPU
   acomp_ctx resources.
 
 - The 2 patch series "mm/damon/core: fix damon_call()/damos_walk() vs
   kdmond exit race" from SeongJae Park addresses unlikely but possible
   leaks and deadlocks in damon_call() and damon_walk().
 
 - The 2 patch series "mm/damon/core: validate damos_quota_goal->nid"
   from SeongJae Park fixes a couple of root-only wild pointer
   dereferences.
 
 - The 2 patch series "Docs/admin-guide/mm/damon: warn commit_inputs vs
   other params race" from SeongJae Park updates the DAMON documentation to
   warn operators about potential races which can occur if the
   commit_inputs parameter is altered at the wrong time.
 
 - The 3 patch series "Minor hmm_test fixes and cleanups" from Alistair
   Popple implements two bugfixes a cleanup for the HMM kernel selftests.
 
 - The 6 patch series "Modify memfd_luo code" from Chenghao Duan provides
   cleanups, simplifications and speedups in the memfd_lou code.
 
 - The 4 patch series "mm, kvm: allow uffd support in guest_memfd" from
   Mike Rapoport enables support for userfaultfd in guest_memfd.
 
 - The 6 patch series "selftests/mm: skip several tests when thp is not
   available" from Chunyu Hu fixes several issues in the selftests code
   which were causing breakage when the tests were run on CONFIG_THP=n
   kernels.
 
 - The 2 patch series "mm/mprotect: micro-optimization work" from Pedro
   Falcato implements a couple of nice speedups for mprotect().
 
 - The 3 patch series "MAINTAINERS: update KHO and LIVE UPDATE entries"
   from Pratyush Yadav reflects 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.
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Merge tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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
  ...
 2026-04-19 08:01:17 -07:00
Pasha Tatashin
68750e820b liveupdate: defer file handler module refcounting to active sessions 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:50 -07:00
Pasha Tatashin
2ab7207e7e liveupdate: make unregister functions return void 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:50 -07:00
Pasha Tatashin
074488008d liveupdate: remove liveupdate_test_unregister() 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:50 -07:00
Pasha Tatashin
5ee1c7d641 liveupdate: auto unregister FLBs on file handler unregistration 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:50 -07:00
Pasha Tatashin
118c390824 liveupdate: remove luo_session_quiesce() 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:50 -07:00
Pasha Tatashin
76be9983df liveupdate: defer FLB module refcounting to active sessions 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:50 -07:00
Pasha Tatashin
6b2b22f7c8 liveupdate: protect FLB lists with luo_register_rwlock 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:49 -07:00
Pasha Tatashin
9e1e185845 liveupdate: protect file handler list with rwsem 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:49 -07:00
Pasha Tatashin
38fb71ace2 liveupdate: synchronize lazy initialization of FLB private state 
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 <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:49 -07:00
Pasha Tatashin
277f4e5e39 liveupdate: safely print untrusted strings 
Patch series "liveupdate: Fix module unloading and unregister API", v3.

This patch series addresses an issue with how LUO handles module reference
counting and unregistration during a module unload (e.g., via rmmod).

Currently, modules that register live update file handlers are pinned for
the entire duration they are registered.  This prevents the modules from
being unloaded gracefully, even when no live update session is in
progress.

Furthermore, if a module is forcefully unloaded, the unregistration
functions return an error (e.g.  -EBUSY) if a session is active, which is
ignored by the kernel's module unload path, leaving dangling pointers in
the LUO global lists.

To resolve these issues, this series introduces the following changes:
1. Adds a global read-write semaphore (luo_register_rwlock) to protect
   the registration lists for both file handlers and FLBs.
2. Reduces the scope of module reference counting for file handlers and
   FLBs. Instead of pinning modules indefinitely upon registration,
   references are now taken only when they are actively used in a live
   update session (e.g., during preservation, retrieval, or
   deserialization).
3. Removes the global luo_session_quiesce() mechanism since module
   unload behavior now handles active sessions implicitly.
4. Introduces auto-unregistration of FLBs during file handler
   unregistration to prevent leaving dangling resources.
5. Changes the unregistration functions to return void instead of
   an error code.
6. Fixes a data race in luo_flb_get_private() by introducing a spinlock
   for thread-safe lazy initialization.
7. Strengthens security by using %.*s when printing untrusted deserialized
   compatible strings and session names to prevent out-of-bounds reads.


This patch (of 10):

Deserialized strings from KHO data (such as file handler compatible
strings and session names) are provided by the previous kernel and might
not be null-terminated if the data is corrupted or maliciously crafted.

When printing these strings in error messages, use the %.*s format
specifier with the maximum buffer size to prevent out-of-bounds reads into
adjacent kernel memory.

Link: https://lore.kernel.org/20260327033335.696621-1-pasha.tatashin@soleen.com
Link: https://lore.kernel.org/20260327033335.696621-2-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:49 -07:00
Pasha Tatashin
00d0b37237 liveupdate: prevent double management of files 
Patch series "liveupdate: prevent double preservation", v4.

Currently, LUO does not prevent the same file from being managed twice
across different active sessions.

Because LUO preserves files of absolutely different types: memfd, and
upcoming vfiofd [1], iommufd [2], guestmefd (and possible kvmfd/cpufd).
There is no common private data or guarantee on how to prevent that the
same file is not preserved twice beside using inode or some slower and
expensive method like hashtables.


This patch (of 4)

Currently, LUO does not prevent the same file from being managed twice
across different active sessions.

Use a global xarray luo_preserved_files to keep track of file identifiers
being preserved by LUO.  Update luo_preserve_file() to check and insert
the file identifier into this xarray when it is preserved, and erase it in
luo_file_unpreserve_files() when it is released.

To allow handlers to define what constitutes a "unique" file (e.g.,
different struct file objects pointing to the same hardware resource), add
a get_id() callback to struct liveupdate_file_ops.  If not provided, the
default identifier is the struct file pointer itself.

This ensures that the same file (or resource) cannot be managed by
multiple sessions.  If another session attempts to preserve an already
managed file, it will now fail with -EBUSY.

Link: https://lore.kernel.org/20260326163943.574070-1-pasha.tatashin@soleen.com
Link: https://lore.kernel.org/20260326163943.574070-2-pasha.tatashin@soleen.com
Link: https://lore.kernel.org/all/20260129212510.967611-1-dmatlack@google.com [1]
Link: https://lore.kernel.org/all/20260203220948.2176157-1-skhawaja@google.com [2]
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Christian Brauner <brauner@kernel.org> 
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:49 -07:00
Breno Leitao
76aa46b9e4 kho: kexec-metadata: track previous kernel chain 
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.

Example output:
    [    0.000000] KHO: exec from: 6.19.0-rc4-next-20260107 (count 1)

Motivation
==========

Bugs that only reproduce when kexecing from specific kernel versions are
difficult to diagnose.  These issues occur when a buggy kernel kexecs into
a new kernel, with the bug manifesting only in the second kernel.

Recent examples include the following commits:

 * commit eb22663125 ("x86/boot: Fix page table access in
   5-level to 4-level paging transition")
 * commit 77d48d39e9 ("efistub/tpm: Use ACPI reclaim memory
   for event log to avoid corruption")
 * commit 64b45dd46e ("x86/efi: skip memattr table on kexec
   boot")

As kexec-based reboots become more common, these version-dependent bugs
are appearing more frequently.  At scale, correlating crashes to the
previous kernel version is challenging, especially when issues only occur
in specific transition scenarios.

Implementation
==============

The kexec metadata is stored as a plain C struct (struct
kho_kexec_metadata) rather than FDT format, for simplicity and direct
field access.  It is registered via kho_add_subtree() as a separate
subtree, keeping it independent from the core KHO ABI.  This design
choice:

 - Keeps the core KHO ABI minimal and stable
 - Allows the metadata format to evolve independently
 - Avoids requiring version bumps for all KHO consumers (LUO, etc.)
   when the metadata format changes

The struct kho_kexec_metadata contains two fields:
 - previous_release: The kernel version that initiated the kexec
 - kexec_count: Number of kexec boots since last cold boot

On cold boot, kexec_count starts at 0 and increments with each kexec.  The
count helps identify issues that only manifest after multiple consecutive
kexec reboots.

[leitao@debian.org: call kho_kexec_metadata_init() for both boot paths]
  Link: https://lore.kernel.org/all/20260309-kho-v8-5-c3abcf4ac750@debian.org/ [1]
  Link: https://lore.kernel.org/20260409-kho_fix_merge_issue-v1-1-710c84ceaa85@debian.org
Link: https://lore.kernel.org/20260316-kho-v9-5-ed6dcd951988@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:48 -07:00
Breno Leitao
062dd306d9 kho: fix kho_in_debugfs_init() to handle non-FDT blobs 
kho_in_debugfs_init() calls fdt_totalsize() to determine blob sizes, which
assumes all blobs are FDTs.  This breaks for non-FDT blobs like struct
kho_kexec_metadata.

Fix this by reading the "blob-size" property from the FDT (persisted by
kho_add_subtree()) instead of calling fdt_totalsize().  Also rename local
variables from fdt_phys/sub_fdt to blob_phys/blob for consistency with the
non-FDT-specific naming.

Link: https://lore.kernel.org/20260316-kho-v9-4-ed6dcd951988@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:48 -07:00
Breno Leitao
85e4139282 kho: persist blob size in KHO FDT 
kho_add_subtree() accepts a size parameter but only forwards it to
debugfs.  The size is not persisted in the KHO FDT, so it is lost across
kexec.  This makes it impossible for the incoming kernel to determine the
blob size without understanding the blob format.

Store the blob size as a "blob-size" property in the KHO FDT alongside the
"preserved-data" physical address.  This allows the receiving kernel to
recover the size for any blob regardless of format.

Also extend kho_retrieve_subtree() with an optional size output parameter
so callers can learn the blob size without needing to understand the blob
format.  Update all callers to pass NULL for the new parameter.

Link: https://lore.kernel.org/20260316-kho-v9-3-ed6dcd951988@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:48 -07:00
Breno Leitao
4916ae3867 kho: rename fdt parameter to blob in kho_add/remove_subtree() 
Since kho_add_subtree() now accepts arbitrary data blobs (not just FDTs),
rename the parameter from 'fdt' to 'blob' to better reflect its purpose. 
Apply the same rename to kho_remove_subtree() for consistency.

Also rename kho_debugfs_fdt_add() and kho_debugfs_fdt_remove() to
kho_debugfs_blob_add() and kho_debugfs_blob_remove() respectively, with
the same parameter rename from 'fdt' to 'blob'.

Link: https://lore.kernel.org/20260316-kho-v9-2-ed6dcd951988@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:48 -07:00
Breno Leitao
d9e4142e76 kho: add size parameter to kho_add_subtree() 
Patch series "kho: history: track previous kernel version and kexec boot
count", v9.

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.

Example
=======
	[    0.000000] Linux version 6.19.0-rc3-upstream-00047-ge5d992347849
	...
	[    0.000000] KHO: exec from: 6.19.0-rc4-next-20260107upstream-00004-g3071b0dc4498 (count 1)

Motivation
==========

Bugs that only reproduce when kexecing from specific kernel versions are
difficult to diagnose.  These issues occur when a buggy kernel kexecs into
a new kernel, with the bug manifesting only in the second kernel.

Recent examples include:

 * eb22663125 ("x86/boot: Fix page table access in 5-level to 4-level paging transition")
 * 77d48d39e9 ("efistub/tpm: Use ACPI reclaim memory for event log to avoid corruption")
 * 64b45dd46e ("x86/efi: skip memattr table on kexec boot")

As kexec-based reboots become more common, these version-dependent bugs
are appearing more frequently.  At scale, correlating crashes to the
previous kernel version is challenging, especially when issues only occur
in specific transition scenarios.

Some bugs manifest only after multiple consecutive kexec reboots. 
Tracking the kexec count helps identify these cases (this metric is
already used by live update sub-system).

KHO provides a reliable mechanism to pass information between kernels.  By
carrying the previous kernel's release string and kexec count forward, we
can print this context at boot time to aid debugging.

The goal of this feature is to have this information being printed in
early boot, so, users can trace back kernel releases in kexec.  Systemd is
not helpful because we cannot assume that the previous kernel has systemd
or even write access to the disk (common when using Linux as bootloaders)


This patch (of 6):

kho_add_subtree() assumes the fdt argument is always an FDT and calls
fdt_totalsize() on it in the debugfs code path.  This assumption will
break if a caller passes arbitrary data instead of an FDT.

When CONFIG_KEXEC_HANDOVER_DEBUGFS is enabled, kho_debugfs_fdt_add() calls
__kho_debugfs_fdt_add(), which executes:

    f->wrapper.size = fdt_totalsize(fdt);

Fix this by adding an explicit size parameter to kho_add_subtree() so
callers specify the blob size.  This allows subtrees to contain arbitrary
data formats, not just FDTs.  Update all callers:

  - memblock.c: use fdt_totalsize(fdt)
  - luo_core.c: use fdt_totalsize(fdt_out)
  - test_kho.c: use fdt_totalsize()
  - kexec_handover.c (root fdt): use fdt_totalsize(kho_out.fdt)

Also update __kho_debugfs_fdt_add() to receive the size explicitly instead
of computing it internally via fdt_totalsize().  In kho_in_debugfs_init(),
pass fdt_totalsize() for the root FDT and sub-blobs since all current
users are FDTs.  A subsequent patch will persist the size in the KHO FDT
so the incoming side can handle non-FDT blobs correctly.

Link: https://lore.kernel.org/20260323110747.193569-1-duanchenghao@kylinos.cn
Link: https://lore.kernel.org/20260316-kho-v9-1-ed6dcd951988@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Suggested-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-18 00:10:48 -07:00
Linus Torvalds
334fbe734e mm.git review status for linus..mm-stable 
Everything:
 
 Total patches:       368
 Reviews/patch:       1.56
 Reviewed rate:       74%
 
 Excluding DAMON:
 
 Total patches:       316
 Reviews/patch:       1.77
 Reviewed rate:       81%
 
 Excluding DAMON and zram:
 
 Total patches:       306
 Reviews/patch:       1.81
 Reviewed rate:       82%
 
 Excluding DAMON, zram and maple_tree:
 
 Total patches:       276
 Reviews/patch:       2.01
 Reviewed rate:       91%
 
 Significant patch series in this merge:
 
 - The 30 patch series "maple_tree: Replace big node with maple copy"
   from Liam Howlett is mainly prepararatory work for ongoing development
   but it does reduce stack usage and is an improvement.
 
 - The 12 patch series "mm, swap: swap table phase III: remove swap_map"
   from Kairui Song offers memory savings by removing the static swap_map.
   It also yields some CPU savings and implements several cleanups.
 
 - The 2 patch series "mm: memfd_luo: preserve file seals" from Pratyush
   Yadav adds file seal preservation to LUO's memfd code.
 
 - The 2 patch series "mm: zswap: add per-memcg stat for incompressible
   pages" from Jiayuan Chen adds additional userspace stats reportng to
   zswap.
 
 - The 4 patch series "arch, mm: consolidate empty_zero_page" from Mike
   Rapoport implements some cleanups for our handling of ZERO_PAGE() and
   zero_pfn.
 
 - The 2 patch series "mm/kmemleak: Improve scan_should_stop()
   implementation" from Zhongqiu Han provides an robustness improvement and
   some cleanups in the kmemleak code.
 
 - The 4 patch series "Improve khugepaged scan logic" from Vernon Yang
   "improves the khugepaged scan logic and reduces CPU consumption by
   prioritizing scanning tasks that access memory frequently".
 
 - The 2 patch series "Make KHO Stateless" from Jason Miu simplifies
   Kexec Handover by "transitioning KHO from an xarray-based metadata
   tracking system with serialization to a radix tree data structure that
   can be passed directly to the next kernel"
 
 - The 3 patch series "mm: vmscan: add PID and cgroup ID to vmscan
   tracepoints" from Thomas Ballasi and Steven Rostedt enhances vmscan's
   tracepointing.
 
 - The 5 patch series "mm: arch/shstk: Common shadow stack mapping helper
   and VM_NOHUGEPAGE" from Catalin Marinas is a cleanup for the shadow
   stack code: remove per-arch code in favour of a generic implementation.
 
 - The 2 patch series "Fix KASAN support for KHO restored vmalloc
   regions" from Pasha Tatashin fixes a WARN() which can be emitted the KHO
   restores a vmalloc area.
 
 - The 4 patch series "mm: Remove stray references to pagevec" from Tal
   Zussman provides several cleanups, mainly udpating references to "struct
   pagevec", which became folio_batch three years ago.
 
 - The 17 patch series "mm: Eliminate fake head pages from vmemmap
   optimization" from Kiryl Shutsemau simplifies the HugeTLB vmemmap
   optimization (HVO) by changing how tail pages encode their relationship
   to the head page.
 
 - The 2 patch series "mm/damon/core: improve DAMOS quota efficiency for
   core layer filters" from SeongJae Park improves two problematic
   behaviors of DAMOS that makes it less efficient when core layer filters
   are used.
 
 - The 3 patch series "mm/damon: strictly respect min_nr_regions" from
   SeongJae Park improves DAMON usability by extending the treatment of the
   min_nr_regions user-settable parameter.
 
 - The 3 patch series "mm/page_alloc: pcp locking cleanup" from Vlastimil
   Babka is a proper fix for a previously hotfixed SMP=n issue.  Code
   simplifications and cleanups ennsed.
 
 - The 16 patch series "mm: cleanups around unmapping / zapping" from
   David Hildenbrand implements "a bunch of cleanups around unmapping and
   zapping.  Mostly simplifications, code movements, documentation and
   renaming of zapping functions".
 
 - The 6 patch series "support batched checking of the young flag for
   MGLRU" from Baolin Wang supports batched checking of the young flag for
   MGLRU.  It's part cleanups; one benchmark shows large performance
   benefits for arm64.
 
 - The 5 patch series "memcg: obj stock and slab stat caching cleanups"
   from Johannes Weiner provides memcg cleanup and robustness improvements.
 
 - The 5 patch series "Allow order zero pages in page reporting" from
   Yuvraj Sakshith enhances page_reporting's free page reporting - it is
   presently and undesirably order-0 pages when reporting free memory.
 
 - The 6 patch series "mm: vma flag tweaks" from Lorenzo Stoakes is
   cleanup work following from the recent conversion of the VMA flags to a
   bitmap.
 
 - The 10 patch series "mm/damon: add optional debugging-purpose sanity
   checks" from SeongJae Park adds some more developer-facing debug checks
   into DAMON core.
 
 - The 2 patch series "mm/damon: test and document power-of-2
   min_region_sz requirement" from SeongJae Park adds an additional DAMON
   kunit test and makes some adjustments to the addr_unit parameter
   handling.
 
 - The 3 patch series "mm/damon/core: make passed_sample_intervals
   comparisons overflow-safe" from SeongJae Park fixes a hard-to-hit time
   overflow issue in DAMON core.
 
 - The 7 patch series "mm/damon: improve/fixup/update ratio calculation,
   test and documentation" from SeongJae Park is a "batch of misc/minor
   improvements and fixups" for DAMON.
 
 - The 4 patch series "mm: move vma_(kernel|mmu)_pagesize() out of
   hugetlb.c" from David Hildenbrand fixes a possible issue with dax-device
   when CONFIG_HUGETLB=n.  Some code movement was required.
 
 - The 6 patch series "zram: recompression cleanups and tweaks" from
   Sergey Senozhatsky provides "a somewhat random mix of fixups,
   recompression cleanups and improvements" in the zram code.
 
 - The 11 patch series "mm/damon: support multiple goal-based quota
   tuning algorithms" from SeongJae Park extend DAMOS quotas goal
   auto-tuning to support multiple tuning algorithms that users can select.
 
 - The 4 patch series "mm: thp: reduce unnecessary
   start_stop_khugepaged()" from Breno Leitao fixes the khugpaged sysfs
   handling so we no longer spam the logs with reams of junk when
   starting/stopping khugepaged.
 
 - The 3 patch series "mm: improve map count checks" from Lorenzo Stoakes
   provides some cleanups and slight fixes in the mremap, mmap and vma
   code.
 
 - The 5 patch series "mm/damon: support addr_unit on default monitoring
   targets for modules" from SeongJae Park extends the use of DAMON core's
   addr_unit tunable.
 
 - The 5 patch series "mm: khugepaged cleanups and mTHP prerequisites"
   from Nico Pache provides cleanups in the khugepaged and is a base for
   Nico's planned khugepaged mTHP support.
 
 - The 15 patch series "mm: memory hot(un)plug and SPARSEMEM cleanups"
   from David Hildenbrand implements code movement and cleanups in the
   memhotplug and sparsemem code.
 
 - The 2 patch series "mm: remove CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE and
   cleanup CONFIG_MIGRATION" from David Hildenbrand rationalizes some
   memhotplug Kconfig support.
 
 - The 6 patch series "change young flag check functions to return bool"
   from Baolin Wang is "a cleanup patchset to change all young flag check
   functions to return bool".
 
 - The 3 patch series "mm/damon/sysfs: fix memory leak and NULL
   dereference issues" from Josh Law and SeongJae Park fixes a few
   potential DAMON bugs.
 
 - The 25 patch series "mm/vma: convert vm_flags_t to vma_flags_t in vma
   code" from "converts a lot of the existing use of the legacy vm_flags_t
   data type to the new vma_flags_t type which replaces it".  Mainly in the
   vma code.
 
 - The 21 patch series "mm: expand mmap_prepare functionality and usage"
   from Lorenzo Stoakes "expands the mmap_prepare functionality, which is
   intended to replace the deprecated f_op->mmap hook which has been the
   source of bugs and security issues for some time".  Cleanups,
   documentation, extension of mmap_prepare into filesystem drivers.
 
 - The 13 patch series "mm/huge_memory: refactor zap_huge_pmd()" from
   Lorenzo Stoakes simplifies and cleans up zap_huge_pmd().  Additional
   cleanups around vm_normal_folio_pmd() and the softleaf functionality are
   performed.
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Merge tag 'mm-stable-2026-04-13-21-45' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

 - "maple_tree: Replace big node with maple copy" (Liam Howlett)

   Mainly prepararatory work for ongoing development but it does reduce
   stack usage and is an improvement.

 - "mm, swap: swap table phase III: remove swap_map" (Kairui Song)

   Offers memory savings by removing the static swap_map. It also yields
   some CPU savings and implements several cleanups.

 - "mm: memfd_luo: preserve file seals" (Pratyush Yadav)

   File seal preservation to LUO's memfd code

 - "mm: zswap: add per-memcg stat for incompressible pages" (Jiayuan
   Chen)

   Additional userspace stats reportng to zswap

 - "arch, mm: consolidate empty_zero_page" (Mike Rapoport)

   Some cleanups for our handling of ZERO_PAGE() and zero_pfn

 - "mm/kmemleak: Improve scan_should_stop() implementation" (Zhongqiu
   Han)

   A robustness improvement and some cleanups in the kmemleak code

 - "Improve khugepaged scan logic" (Vernon Yang)

   Improve khugepaged scan logic and reduce CPU consumption by
   prioritizing scanning tasks that access memory frequently

 - "Make KHO Stateless" (Jason Miu)

   Simplify Kexec Handover by transitioning KHO from an xarray-based
   metadata tracking system with serialization to a radix tree data
   structure that can be passed directly to the next kernel

 - "mm: vmscan: add PID and cgroup ID to vmscan tracepoints" (Thomas
   Ballasi and Steven Rostedt)

   Enhance vmscan's tracepointing

 - "mm: arch/shstk: Common shadow stack mapping helper and
   VM_NOHUGEPAGE" (Catalin Marinas)

   Cleanup for the shadow stack code: remove per-arch code in favour of
   a generic implementation

 - "Fix KASAN support for KHO restored vmalloc regions" (Pasha Tatashin)

   Fix a WARN() which can be emitted the KHO restores a vmalloc area

 - "mm: Remove stray references to pagevec" (Tal Zussman)

   Several cleanups, mainly udpating references to "struct pagevec",
   which became folio_batch three years ago

 - "mm: Eliminate fake head pages from vmemmap optimization" (Kiryl
   Shutsemau)

   Simplify the HugeTLB vmemmap optimization (HVO) by changing how tail
   pages encode their relationship to the head page

 - "mm/damon/core: improve DAMOS quota efficiency for core layer
   filters" (SeongJae Park)

   Improve two problematic behaviors of DAMOS that makes it less
   efficient when core layer filters are used

 - "mm/damon: strictly respect min_nr_regions" (SeongJae Park)

   Improve DAMON usability by extending the treatment of the
   min_nr_regions user-settable parameter

 - "mm/page_alloc: pcp locking cleanup" (Vlastimil Babka)

   The proper fix for a previously hotfixed SMP=n issue. Code
   simplifications and cleanups ensued

 - "mm: cleanups around unmapping / zapping" (David Hildenbrand)

   A bunch of cleanups around unmapping and zapping. Mostly
   simplifications, code movements, documentation and renaming of
   zapping functions

 - "support batched checking of the young flag for MGLRU" (Baolin Wang)

   Batched checking of the young flag for MGLRU. It's part cleanups; one
   benchmark shows large performance benefits for arm64

 - "memcg: obj stock and slab stat caching cleanups" (Johannes Weiner)

   memcg cleanup and robustness improvements

 - "Allow order zero pages in page reporting" (Yuvraj Sakshith)

   Enhance free page reporting - it is presently and undesirably order-0
   pages when reporting free memory.

 - "mm: vma flag tweaks" (Lorenzo Stoakes)

   Cleanup work following from the recent conversion of the VMA flags to
   a bitmap

 - "mm/damon: add optional debugging-purpose sanity checks" (SeongJae
   Park)

   Add some more developer-facing debug checks into DAMON core

 - "mm/damon: test and document power-of-2 min_region_sz requirement"
   (SeongJae Park)

   An additional DAMON kunit test and makes some adjustments to the
   addr_unit parameter handling

 - "mm/damon/core: make passed_sample_intervals comparisons
   overflow-safe" (SeongJae Park)

   Fix a hard-to-hit time overflow issue in DAMON core

 - "mm/damon: improve/fixup/update ratio calculation, test and
   documentation" (SeongJae Park)

   A batch of misc/minor improvements and fixups for DAMON

 - "mm: move vma_(kernel|mmu)_pagesize() out of hugetlb.c" (David
   Hildenbrand)

   Fix a possible issue with dax-device when CONFIG_HUGETLB=n. Some code
   movement was required.

 - "zram: recompression cleanups and tweaks" (Sergey Senozhatsky)

   A somewhat random mix of fixups, recompression cleanups and
   improvements in the zram code

 - "mm/damon: support multiple goal-based quota tuning algorithms"
   (SeongJae Park)

   Extend DAMOS quotas goal auto-tuning to support multiple tuning
   algorithms that users can select

 - "mm: thp: reduce unnecessary start_stop_khugepaged()" (Breno Leitao)

   Fix the khugpaged sysfs handling so we no longer spam the logs with
   reams of junk when starting/stopping khugepaged

 - "mm: improve map count checks" (Lorenzo Stoakes)

   Provide some cleanups and slight fixes in the mremap, mmap and vma
   code

 - "mm/damon: support addr_unit on default monitoring targets for
   modules" (SeongJae Park)

   Extend the use of DAMON core's addr_unit tunable

 - "mm: khugepaged cleanups and mTHP prerequisites" (Nico Pache)

   Cleanups to khugepaged and is a base for Nico's planned khugepaged
   mTHP support

 - "mm: memory hot(un)plug and SPARSEMEM cleanups" (David Hildenbrand)

   Code movement and cleanups in the memhotplug and sparsemem code

 - "mm: remove CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE and cleanup
   CONFIG_MIGRATION" (David Hildenbrand)

   Rationalize some memhotplug Kconfig support

 - "change young flag check functions to return bool" (Baolin Wang)

   Cleanups to change all young flag check functions to return bool

 - "mm/damon/sysfs: fix memory leak and NULL dereference issues" (Josh
   Law and SeongJae Park)

   Fix a few potential DAMON bugs

 - "mm/vma: convert vm_flags_t to vma_flags_t in vma code" (Lorenzo
   Stoakes)

   Convert a lot of the existing use of the legacy vm_flags_t data type
   to the new vma_flags_t type which replaces it. Mainly in the vma
   code.

 - "mm: expand mmap_prepare functionality and usage" (Lorenzo Stoakes)

   Expand the mmap_prepare functionality, which is intended to replace
   the deprecated f_op->mmap hook which has been the source of bugs and
   security issues for some time. Cleanups, documentation, extension of
   mmap_prepare into filesystem drivers

 - "mm/huge_memory: refactor zap_huge_pmd()" (Lorenzo Stoakes)

   Simplify and clean up zap_huge_pmd(). Additional cleanups around
   vm_normal_folio_pmd() and the softleaf functionality are performed.

* tag 'mm-stable-2026-04-13-21-45' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits)
  mm: fix deferred split queue races during migration
  mm/khugepaged: fix issue with tracking lock
  mm/huge_memory: add and use has_deposited_pgtable()
  mm/huge_memory: add and use normal_or_softleaf_folio_pmd()
  mm: add softleaf_is_valid_pmd_entry(), pmd_to_softleaf_folio()
  mm/huge_memory: separate out the folio part of zap_huge_pmd()
  mm/huge_memory: use mm instead of tlb->mm
  mm/huge_memory: remove unnecessary sanity checks
  mm/huge_memory: deduplicate zap deposited table call
  mm/huge_memory: remove unnecessary VM_BUG_ON_PAGE()
  mm/huge_memory: add a common exit path to zap_huge_pmd()
  mm/huge_memory: handle buggy PMD entry in zap_huge_pmd()
  mm/huge_memory: have zap_huge_pmd return a boolean, add kdoc
  mm/huge: avoid big else branch in zap_huge_pmd()
  mm/huge_memory: simplify vma_is_specal_huge()
  mm: on remap assert that input range within the proposed VMA
  mm: add mmap_action_map_kernel_pages[_full]()
  uio: replace deprecated mmap hook with mmap_prepare in uio_info
  drivers: hv: vmbus: replace deprecated mmap hook with mmap_prepare
  mm: allow handling of stacked mmap_prepare hooks in more drivers
  ...
 2026-04-15 12:59:16 -07:00
Leo Timmins
307e0c5859 liveupdate: propagate file deserialization failures 
luo_session_deserialize() ignored the return value from
luo_file_deserialize().  As a result, a session could be left partially
restored even though the /dev/liveupdate open path treats deserialization
failures as fatal.

Propagate the error so a failed file deserialization aborts session
deserialization instead of silently continuing.

Link: https://lkml.kernel.org/r/20260325044608.8407-1-leotimmins1974@gmail.com
Link: https://lkml.kernel.org/r/20260325044608.8407-2-leotimmins1974@gmail.com
Fixes: 16cec0d265 ("liveupdate: luo_session: add ioctls for file preservation")
Signed-off-by: Leo Timmins <leotimmins1974@gmail.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-06 11:13:42 -07:00
Pratyush Yadav
22bdab8e98 kho: drop restriction on maximum page order 
KHO currently restricts the maximum order of a restored page to the
maximum order supported by the buddy allocator.  While this works fine for
much of the data passed across kexec, it is possible to have pages larger
than MAX_PAGE_ORDER.

For one, it is possible to get a larger order when using
kho_preserve_pages() if the number of pages is large enough, since it
tries to combine multiple aligned 0-order preservations into one higher
order preservation.

For another, upcoming support for hugepages can have gigantic hugepages
being preserved over KHO.

There is no real reason for this limit.  The KHO preservation machinery
can handle any page order.  Remove this artificial restriction on max page
order.

Link: https://lkml.kernel.org/r/20260309123410.382308-2-pratyush@kernel.org
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:24 -07:00
Pratyush Yadav (Google)
91e74fa8b1 kho: make sure preservations do not span multiple NUMA nodes 
The KHO restoration machinery is not capable of dealing with preservations
that span multiple NUMA nodes.  kho_preserve_folio() guarantees the
preservation will only span one NUMA node since folios can't span multiple
nodes.

This leaves kho_preserve_pages().  While semantically kho_preserve_pages()
only deals with 0-order pages, so all preservations should be single page
only, in practice it combines preservations to higher orders for
efficiency.  This can result in a preservation spanning multiple nodes. 
Break up the preservations into a smaller order if that happens.

Link: https://lkml.kernel.org/r/20260309123410.382308-1-pratyush@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:24 -07:00
Pasha Tatashin
019fc36872 kho: fix KASAN support for restored vmalloc regions 
Restored vmalloc regions are currently not properly marked for KASAN,
causing KASAN to treat accesses to these regions as out-of-bounds.

Fix this by properly unpoisoning the restored vmalloc area using
kasan_unpoison_vmalloc().  This requires setting the VM_UNINITIALIZED flag
during the initial area allocation and clearing it after the pages have
been mapped and unpoisoned, using the clear_vm_uninitialized_flag()
helper.

Link: https://lkml.kernel.org/r/20260225223857.1714801-3-pasha.tatashin@soleen.com
Fixes: a667300bd5 ("kho: add support for preserving vmalloc allocations")
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reported-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Tested-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:06 -07:00
Jason Miu
6b0dd42d76 kho: remove finalize state and clients 
Eliminate the `kho_finalize()` function and its associated state from the
KHO subsystem.  The transition to a radix tree for memory tracking makes
the explicit "finalize" state and its serialization step obsolete.

Remove the `kho_finalize()` and `kho_finalized()` APIs and their stub
implementations.  Update KHO client code and the debugfs interface to no
longer call or depend on the `kho_finalize()` mechanism.

Complete the move towards a stateless KHO, simplifying the overall design
by removing unnecessary state management.

Link: https://lkml.kernel.org/r/20260206021428.3386442-3-jasonmiu@google.com
Signed-off-by: Jason Miu <jasonmiu@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:04 -07:00
Jason Miu
3f2ad90060 kho: adopt radix tree for preserved memory tracking 
Patch series "Make KHO Stateless", v9.

This series transitions KHO from an xarray-based metadata tracking system
with serialization to a radix tree data structure that can be passed
directly to the next kernel.

The key motivations for this change are to:
- Eliminate the need for data serialization before kexec.
- Remove the KHO finalize state.
- Pass preservation metadata more directly to the next kernel via the FDT.

The new approach uses a radix tree to mark preserved pages.  A page's
physical address and its order are encoded into a single value.  The tree
is composed of multiple levels of page-sized tables, with leaf nodes being
bitmaps where each set bit represents a preserved page.  The physical
address of the radix tree's root is passed in the FDT, allowing the next
kernel to reconstruct the preserved memory map.

This series is broken down into the following patches:

1.  kho: Adopt radix tree for preserved memory tracking:    
    Replaces the xarray-based tracker with the new radix tree
    implementation and increments the ABI version.

2.  kho: Remove finalize state and clients:
    Removes the now-obsolete kho_finalize() function and its usage
    from client code and debugfs.


This patch (of 2):

Introduce a radix tree implementation for tracking preserved memory pages
and switch the KHO memory tracking mechanism to use it.  This lays the
groundwork for a stateless KHO implementation that eliminates the need for
serialization and the associated "finalize" state.

This patch introduces the core radix tree data structures and constants to
the KHO ABI.  It adds the radix tree node and leaf structures, along with
documentation for the radix tree key encoding scheme that combines a
page's physical address and order.

To support broader use by other kernel subsystems, such as hugetlb
preservation, the core radix tree manipulation functions are exported as a
public API.

The xarray-based memory tracking is replaced with this new radix tree
implementation.  The core KHO preservation and unpreservation functions
are wired up to use the radix tree helpers.  On boot, the second kernel
restores the preserved memory map by walking the radix tree whose root
physical address is passed via the FDT.

The ABI `compatible` version is bumped to "kho-v2" to reflect the
structural changes in the preserved memory map and sub-FDT property names.
This includes renaming "fdt" to "preserved-data" to better reflect that
preserved state may use formats other than FDT.

[ran.xiaokai@zte.com.cn: fix child node parsing for debugfs in/sub_fdts]
  Link: https://lkml.kernel.org/r/20260309033530.244508-1-ranxiaokai627@163.com
Link: https://lkml.kernel.org/r/20260206021428.3386442-1-jasonmiu@google.com
Link: https://lkml.kernel.org/r/20260206021428.3386442-2-jasonmiu@google.com
Signed-off-by: Jason Miu <jasonmiu@google.com>
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:04 -07:00
Pratyush Yadav (Google)
63de231ef0 kho: move alloc tag init to kho_init_{folio,pages}() 
Commit 8f1081892d ("kho: simplify page initialization in
kho_restore_page()") cleaned up the page initialization logic by moving
the folio and 0-order-page paths into separate functions.  It missed
moving the alloc tag initialization.

Do it now to keep the two paths cleanly separated.  While at it, touch up
the comments to be a tiny bit shorter (mainly so it doesn't end up
splitting into a multiline comment).  This is purely a cosmetic change and
there should be no change in behaviour.

Link: https://lkml.kernel.org/r/20260213085914.2778107-1-pratyush@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:03 -07:00
Pratyush Yadav (Google)
f85b1c6af5 liveupdate: luo_file: remember retrieve() status 
LUO keeps track of successful retrieve attempts on a LUO file.  It does so
to avoid multiple retrievals of the same file.  Multiple retrievals cause
problems because once the file is retrieved, the serialized data
structures are likely freed and the file is likely in a very different
state from what the code expects.

The retrieve boolean in struct luo_file keeps track of this, and is passed
to the finish callback so it knows what work was already done and what it
has left to do.

All this works well when retrieve succeeds.  When it fails,
luo_retrieve_file() returns the error immediately, without ever storing
anywhere that a retrieve was attempted or what its error code was.  This
results in an errored LIVEUPDATE_SESSION_RETRIEVE_FD ioctl to userspace,
but nothing prevents it from trying this again.

The retry is problematic for much of the same reasons listed above.  The
file is likely in a very different state than what the retrieve logic
normally expects, and it might even have freed some serialization data
structures.  Attempting to access them or free them again is going to
break things.

For example, if memfd managed to restore 8 of its 10 folios, but fails on
the 9th, a subsequent retrieve attempt will try to call
kho_restore_folio() on the first folio again, and that will fail with a
warning since it is an invalid operation.

Apart from the retry, finish() also breaks.  Since on failure the
retrieved bool in luo_file is never touched, the finish() call on session
close will tell the file handler that retrieve was never attempted, and it
will try to access or free the data structures that might not exist, much
in the same way as the retry attempt.

There is no sane way of attempting the retrieve again.  Remember the error
retrieve returned and directly return it on a retry.  Also pass this
status code to finish() so it can make the right decision on the work it
needs to do.

This is done by changing the bool to an integer.  A value of 0 means
retrieve was never attempted, a positive value means it succeeded, and a
negative value means it failed and the error code is the value.

Link: https://lkml.kernel.org/r/20260216132221.987987-1-pratyush@kernel.org
Fixes: 7c722a7f44 ("liveupdate: luo_file: implement file systems callbacks")
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-24 11:13:26 -08:00
Linus Torvalds
bf4afc53b7 Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 
This was done entirely with mindless brute force, using

    git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
        xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'

to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.

Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.

For the same reason the 'flex' versions will be done as a separate
conversion.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2026-02-21 17:09:51 -08:00
Kees Cook
69050f8d6d treewide: Replace kmalloc with kmalloc_obj for non-scalar types 
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:

Single allocations:	kmalloc(sizeof(TYPE), ...)
are replaced with:	kmalloc_obj(TYPE, ...)

Array allocations:	kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with:	kmalloc_objs(TYPE, COUNT, ...)

Flex array allocations:	kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with:	kmalloc_flex(*PTR, FAM, COUNT, ...)

(where TYPE may also be *VAR)

The resulting allocations no longer return "void *", instead returning
"TYPE *".

Signed-off-by: Kees Cook <kees@kernel.org>
 2026-02-21 01:02:28 -08:00
Linus Torvalds
2b7a25df82 mm.git review status for linus..mm-nonmm-stable 
Total patches:       7
 Reviews/patch:       0.57
 Reviewed rate:       42%
 
 - The 2 patch series "two fixes in kho_populate()" from Ran Xiaokai
   fixes a couple of not-major issues in the kexec handover code.
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Merge tag 'mm-nonmm-stable-2026-02-18-19-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull more non-MM updates from Andrew Morton:

 - "two fixes in kho_populate()" fixes a couple of not-major issues in
   the kexec handover code (Ran Xiaokai)

 - misc singletons

* tag 'mm-nonmm-stable-2026-02-18-19-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  lib/group_cpus: handle const qualifier from clusters allocation type
  kho: remove unnecessary WARN_ON(err) in kho_populate()
  kho: fix missing early_memunmap() call in kho_populate()
  scripts/gdb: implement x86_page_ops in mm.py
  objpool: fix the overestimation of object pooling metadata size
  selftests/memfd: use IPC semaphore instead of SIGSTOP/SIGCONT
  delayacct: fix build regression on accounting tool
 2026-02-18 21:40:16 -08:00
Ran Xiaokai
f7a553b813 kho: remove unnecessary WARN_ON(err) in kho_populate() 
The following pr_warn() provides detailed error and location information,
WARN_ON(err) adds no additional debugging value, so remove the redundant
WARN_ON() call.

Link: https://lkml.kernel.org/r/20260212111146.210086-3-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-12 15:45:58 -08:00
Ran Xiaokai
34df6c4734 kho: fix missing early_memunmap() call in kho_populate() 
Patch series "two fixes in kho_populate()", v3.


This patch (of 2):

kho_populate() returns without calling early_memunmap() on success path,
this will cause early ioremap virtual address space leak.

Link: https://lkml.kernel.org/r/20260212111146.210086-1-ranxiaokai627@163.com
Link: https://lkml.kernel.org/r/20260212111146.210086-2-ranxiaokai627@163.com
Fixes: b50634c5e8 ("kho: cleanup error handling in kho_populate()")
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-12 15:45:57 -08:00
Linus Torvalds
136114e0ab mm.git review status for linus..mm-nonmm-stable 
Total patches:       107
 Reviews/patch:       1.07
 Reviewed rate:       67%
 
 - The 2 patch series "ocfs2: give ocfs2 the ability to reclaim
   suballocator free bg" from Heming Zhao saves disk space by teaching
   ocfs2 to reclaim suballocator block group space.
 
 - The 4 patch series "Add ARRAY_END(), and use it to fix off-by-one
   bugs" from Alejandro Colomar adds the ARRAY_END() macro and uses it in
   various places.
 
 - The 2 patch series "vmcoreinfo: support VMCOREINFO_BYTES larger than
   PAGE_SIZE" from Pnina Feder makes the vmcore code future-safe, if
   VMCOREINFO_BYTES ever exceeds the page size.
 
 - The 7 patch series "kallsyms: Prevent invalid access when showing
   module buildid" from Petr Mladek cleans up kallsyms code related to
   module buildid and fixes an invalid access crash when printing
   backtraces.
 
 - The 3 patch series "Address page fault in
   ima_restore_measurement_list()" from Harshit Mogalapalli fixes a
   kexec-related crash that can occur when booting the second-stage kernel
   on x86.
 
 - The 6 patch series "kho: ABI headers and Documentation updates" from
   Mike Rapoport updates the kexec handover ABI documentation.
 
 - The 4 patch series "Align atomic storage" from Finn Thain adds the
   __aligned attribute to atomic_t and atomic64_t definitions to get
   natural alignment of both types on csky, m68k, microblaze, nios2,
   openrisc and sh.
 
 - The 2 patch series "kho: clean up page initialization logic" from
   Pratyush Yadav simplifies the page initialization logic in
   kho_restore_page().
 
 - The 6 patch series "Unload linux/kernel.h" from Yury Norov moves
   several things out of kernel.h and into more appropriate places.
 
 - The 7 patch series "don't abuse task_struct.group_leader" from Oleg
   Nesterov removes the usage of ->group_leader when it is "obviously
   unnecessary".
 
 - The 5 patch series "list private v2 & luo flb" from Pasha Tatashin
   adds some infrastructure improvements to the live update orchestrator.
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Merge tag 'mm-nonmm-stable-2026-02-12-10-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull non-MM updates from Andrew Morton:

 - "ocfs2: give ocfs2 the ability to reclaim suballocator free bg" saves
   disk space by teaching ocfs2 to reclaim suballocator block group
   space (Heming Zhao)

 - "Add ARRAY_END(), and use it to fix off-by-one bugs" adds the
   ARRAY_END() macro and uses it in various places (Alejandro Colomar)

 - "vmcoreinfo: support VMCOREINFO_BYTES larger than PAGE_SIZE" makes
   the vmcore code future-safe, if VMCOREINFO_BYTES ever exceeds the
   page size (Pnina Feder)

 - "kallsyms: Prevent invalid access when showing module buildid" cleans
   up kallsyms code related to module buildid and fixes an invalid
   access crash when printing backtraces (Petr Mladek)

 - "Address page fault in ima_restore_measurement_list()" fixes a
   kexec-related crash that can occur when booting the second-stage
   kernel on x86 (Harshit Mogalapalli)

 - "kho: ABI headers and Documentation updates" updates the kexec
   handover ABI documentation (Mike Rapoport)

 - "Align atomic storage" adds the __aligned attribute to atomic_t and
   atomic64_t definitions to get natural alignment of both types on
   csky, m68k, microblaze, nios2, openrisc and sh (Finn Thain)

 - "kho: clean up page initialization logic" simplifies the page
   initialization logic in kho_restore_page() (Pratyush Yadav)

 - "Unload linux/kernel.h" moves several things out of kernel.h and into
   more appropriate places (Yury Norov)

 - "don't abuse task_struct.group_leader" removes the usage of
   ->group_leader when it is "obviously unnecessary" (Oleg Nesterov)

 - "list private v2 & luo flb" adds some infrastructure improvements to
   the live update orchestrator (Pasha Tatashin)

* tag 'mm-nonmm-stable-2026-02-12-10-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (107 commits)
  watchdog/hardlockup: simplify perf event probe and remove per-cpu dependency
  procfs: fix missing RCU protection when reading real_parent in do_task_stat()
  watchdog/softlockup: fix sample ring index wrap in need_counting_irqs()
  kcsan, compiler_types: avoid duplicate type issues in BPF Type Format
  kho: fix doc for kho_restore_pages()
  tests/liveupdate: add in-kernel liveupdate test
  liveupdate: luo_flb: introduce File-Lifecycle-Bound global state
  liveupdate: luo_file: Use private list
  list: add kunit test for private list primitives
  list: add primitives for private list manipulations
  delayacct: fix uapi timespec64 definition
  panic: add panic_force_cpu= parameter to redirect panic to a specific CPU
  netclassid: use thread_group_leader(p) in update_classid_task()
  RDMA/umem: don't abuse current->group_leader
  drm/pan*: don't abuse current->group_leader
  drm/amd: kill the outdated "Only the pthreads threading model is supported" checks
  drm/amdgpu: don't abuse current->group_leader
  android/binder: use same_thread_group(proc->tsk, current) in binder_mmap()
  android/binder: don't abuse current->group_leader
  kho: skip memoryless NUMA nodes when reserving scratch areas
  ...
 2026-02-12 12:13:01 -08:00
Tycho Andersen (AMD)
0758293d5d kho: fix doc for kho_restore_pages() 
This function returns NULL if kho_restore_page() returns NULL, which
happens in a couple of corner cases.  It never returns an error code.

Link: https://lkml.kernel.org/r/20260123190506.1058669-1-tycho@kernel.org
Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-08 00:13:34 -08:00
Pasha Tatashin
f653ff7af9 tests/liveupdate: add in-kernel liveupdate test 
Introduce an in-kernel test module to validate the core logic of the Live
Update Orchestrator's File-Lifecycle-Bound feature.  This provides a
low-level, controlled environment to test FLB registration and callback
invocation without requiring userspace interaction or actual kexec
reboots.

The test is enabled by the CONFIG_LIVEUPDATE_TEST Kconfig option.

Link: https://lkml.kernel.org/r/20251218155752.3045808-6-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Gow <davidgow@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Cc: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-08 00:13:33 -08:00
Pasha Tatashin
cab056f2aa liveupdate: luo_flb: introduce File-Lifecycle-Bound global state 
Introduce a mechanism for managing global kernel state whose lifecycle is
tied to the preservation of one or more files.  This is necessary for
subsystems where multiple preserved file descriptors depend on a single,
shared underlying resource.

An example is HugeTLB, where multiple file descriptors such as memfd and
guest_memfd may rely on the state of a single HugeTLB subsystem. 
Preserving this state for each individual file would be redundant and
incorrect.  The state should be preserved only once when the first file is
preserved, and restored/finished only once the last file is handled.

This patch introduces File-Lifecycle-Bound (FLB) objects to solve this
problem.  An FLB is a global, reference-counted object with a defined set
of operations:

- A file handler (struct liveupdate_file_handler) declares a dependency
  on one or more FLBs via a new registration function,
  liveupdate_register_flb().
- When the first file depending on an FLB is preserved, the FLB's
  .preserve() callback is invoked to save the shared global state. The
  reference count is then incremented for each subsequent file.
- Conversely, when the last file is unpreserved (before reboot) or
  finished (after reboot), the FLB's .unpreserve() or .finish() callback
  is invoked to clean up the global resource.

The implementation includes:

- A new set of ABI definitions (luo_flb_ser, luo_flb_head_ser) and a
  corresponding FDT node (luo-flb) to serialize the state of all active
  FLBs and pass them via Kexec Handover.
- Core logic in luo_flb.c to manage FLB registration, reference
  counting, and the invocation of lifecycle callbacks.
- An API (liveupdate_flb_get/_incoming/_outgoing) for other kernel
  subsystems to safely access the live object managed by an FLB, both
  before and after the live update.

This framework provides the necessary infrastructure for more complex
subsystems like IOMMU, VFIO, and KVM to integrate with the Live Update
Orchestrator.

Link: https://lkml.kernel.org/r/20251218155752.3045808-5-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Gow <davidgow@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Cc: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-08 00:13:33 -08:00
Pasha Tatashin
6845645eef liveupdate: luo_file: Use private list 
Switch LUO to use the private list iterators.

Link: https://lkml.kernel.org/r/20251218155752.3045808-4-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Gow <davidgow@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Cc: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-08 00:13:33 -08:00
Pratyush Yadav (Google)
011d4e52a7 liveupdate: luo_file: do not clear serialized_data on unfreeze 
Patch series "liveupdate: fixes in error handling".

This series contains some fixes in LUO's error handling paths.

The first patch deals with failed freeze() attempts.  The cleanup path
calls unfreeze, and that clears some data needed by later unpreserve
calls.

The second patch is a bit more involved.  It deals with failed retrieve()
attempts.  To do so properly, it reworks some of the error handling logic
in luo_file core.

Both these fixes are "theoretical" -- in the sense that I have not been
able to reproduce either of them in normal operation.  The only supported
file type right now is memfd, and there is nothing userspace can do right
now to make it fail its retrieve or freeze.  I need to make the retrieve
or freeze fail by artificially injecting errors.  The injected errors
trigger a use-after-free and a double-free.

That said, once more complex file handlers are added or memfd preservation
is used in ways not currently expected or covered by the tests, we will be
able to see them on real systems.


This patch (of 2):

The unfreeze operation is supposed to undo the effects of the freeze
operation.  serialized_data is not set by freeze, but by preserve. 
Consequently, the unpreserve operation needs to access serialized_data to
undo the effects of the preserve operation.  This includes freeing the
serialized data structures for example.

If a freeze callback fails, unfreeze is called for all frozen files.  This
would clear serialized_data for them.  Since live update has failed, it
can be expected that userspace aborts, releasing all sessions.  When the
sessions are released, unpreserve will be called for all files.  The
unfrozen files will see 0 in their serialized_data.  This is not expected
by file handlers, and they might either fail, leaking data and state, or
might even crash or cause invalid memory access.

Do not clear serialized_data on unfreeze so it gets passed on to
unpreserve.  There is no need to clear it on unpreserve since luo_file
will be freed immediately after.

Link: https://lkml.kernel.org/r/20260126230302.2936817-1-pratyush@kernel.org
Link: https://lkml.kernel.org/r/20260126230302.2936817-2-pratyush@kernel.org
Fixes: 7c722a7f44 ("liveupdate: luo_file: implement file systems callbacks")
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-02-02 18:43:55 -08:00
Evangelos Petrongonas
427b2535f5 kho: skip memoryless NUMA nodes when reserving scratch areas 
kho_reserve_scratch() iterates over all online NUMA nodes to allocate
per-node scratch memory.  On systems with memoryless NUMA nodes (nodes
that have CPUs but no memory), memblock_alloc_range_nid() fails because
there is no memory available on that node.  This causes KHO initialization
to fail and kho_enable to be set to false.

Some ARM64 systems have NUMA topologies where certain nodes contain only
CPUs without any associated memory.  These configurations are valid and
should not prevent KHO from functioning.

Fix this by only counting nodes that have memory (N_MEMORY state) and skip
memoryless nodes in the per-node scratch allocation loop.

Link: https://lkml.kernel.org/r/20260120175913.34368-1-epetron@amazon.de
Fixes: 3dc92c3114 ("kexec: add Kexec HandOver (KHO) generation helpers").
Signed-off-by: Evangelos Petrongonas <epetron@amazon.de>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 16:16:08 -08:00
Mike Rapoport (Microsoft)
b50634c5e8 kho: cleanup error handling in kho_populate() 
* use dedicated labels for error handling instead of checking if a pointer
  is not null to decide if it should be unmapped
* drop assignment of values to err that are only used to print a numeric
  error code, there are pr_warn()s for each failure already so printing a
  numeric error code in the next line does not add anything useful

Link: https://lkml.kernel.org/r/20260122121757.575987-1-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 16:16:08 -08:00
Pratyush Yadav
8f1081892d kho: simplify page initialization in kho_restore_page() 
When restoring a page (from kho_restore_pages()) or folio (from
kho_restore_folio()), KHO must initialize the struct page.  The
initialization differs slightly depending on if a folio is requested or a
set of 0-order pages is requested.

Conceptually, it is quite simple to understand.  When restoring 0-order
pages, each page gets a refcount of 1 and that's it.  When restoring a
folio, head page gets a refcount of 1 and tail pages get 0.

kho_restore_page() tries to combine the two separate initialization flow
into one piece of code.  While it works fine, it is more complicated to
read than it needs to be.  Make the code simpler by splitting the two
initalization paths into two separate functions.  This improves
readability by clearly showing how each type must be initialized.

Link: https://lkml.kernel.org/r/20260116112217.915803-3-pratyush@kernel.org
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 16:16:04 -08:00
Pratyush Yadav
840fe43d37 kho: use unsigned long for nr_pages 
Patch series "kho: clean up page initialization logic", v2.

This series simplifies the page initialization logic in
kho_restore_page().  It was originally only a single patch [0], but on
Pasha's suggestion, I added another patch to use unsigned long for
nr_pages.

Technically speaking, the patches aren't related and can be applied
independently, but bundling them together since patch 2 relies on 1 and it
is easier to manage them this way.


This patch (of 2):

With 4k pages, a 32-bit nr_pages can span up to 16 TiB.  While it is a
lot, there exist systems with terabytes of RAM.  gup is also moving to
using long for nr_pages.  Use unsigned long and make KHO future-proof.

Link: https://lkml.kernel.org/r/20260116112217.915803-1-pratyush@kernel.org
Link: https://lkml.kernel.org/r/20260116112217.915803-2-pratyush@kernel.org
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-31 16:16:04 -08:00
Andrew Morton
2eec08ff09 Merge branch 'mm-hotfixes-stable' into mm-nonmm-stable to pick up changes 
required to merge "kho: use unsigned long for nr_pages".
 2026-01-31 16:12:21 -08:00
Pratyush Yadav (Google)
6ca9de3600 kho: print which scratch buffer failed to be reserved 
When scratch area fails to reserve, KHO prints a message indicating that. 
But it doesn't say which scratch failed to allocate.  This can be useful
information for debugging.  Even more so when the failure is hard to
reproduce.

Along with the current message, also print which exact scratch area failed
to be reserved.

Link: https://lkml.kernel.org/r/20260116165416.1262531-1-pratyush@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Matlack <dmatlack@google.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-26 19:07:15 -08:00
Long Wei
25929dae28 kho: remove duplicate header file references 
kexec_handover_internal.h is included twice in kexec_handover.c.  Remove
the redundant first inclusion to eliminate the duplication.

Link: https://lkml.kernel.org/r/20251216114400.2677311-1-longwei27@huawei.com
Signed-off-by: Long Wei <longwei27@huawei.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: hewenliang <hewenliang4@huawei.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-26 19:07:13 -08:00
Jason Miu
ac2d8102c4 kho: relocate vmalloc preservation structure to KHO ABI header 
The `struct kho_vmalloc` defines the in-memory layout for preserving
vmalloc regions across kexec.  This layout is a contract between kernels
and part of the KHO ABI.

To reflect this relationship, the related structs and helper macros are
relocated to the ABI header, `include/linux/kho/abi/kexec_handover.h`. 
This move places the structure's definition under the protection of the
KHO_FDT_COMPATIBLE version string.

The structure and its components are now also documented within the ABI
header to describe the contract and prevent ABI breaks.

[rppt@kernel.org: update comment, per Pratyush]
  Link: https://lkml.kernel.org/r/aW_Mqp6HcqLwQImS@kernel.org
Link: https://lkml.kernel.org/r/20260105165839.285270-6-rppt@kernel.org
Signed-off-by: Jason Miu <jasonmiu@google.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-26 19:07:12 -08:00
Jason Miu
5e1ea1e27b kho: introduce KHO FDT ABI header 
Introduce the `include/linux/kho/abi/kexec_handover.h` header file, which
defines the stable ABI for the KHO mechanism.  This header specifies how
preserved data is passed between kernels using an FDT.

The ABI contract includes the FDT structure, node properties, and the
"kho-v1" compatible string.  By centralizing these definitions, this
header serves as the foundational agreement for inter-kernel communication
of preserved states, ensuring forward compatibility and preventing
misinterpretation of data across kexec transitions.

Since the ABI definitions are now centralized in the header files, the
YAML files that previously described the FDT interfaces are redundant. 
These redundant files have therefore been removed.

Link: https://lkml.kernel.org/r/20260105165839.285270-5-rppt@kernel.org
Signed-off-by: Jason Miu <jasonmiu@google.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-26 19:07:12 -08:00
Mike Rapoport (Microsoft)
a6f4e56828 kho: docs: combine concepts and FDT documentation 
Currently index.rst in KHO documentation looks empty and sad as it only
contains links to "Kexec Handover Concepts" and "KHO FDT" chapters.

Inline contents of these chapters into index.rst to provide a single
coherent chapter describing KHO.

While on it, drop parts of the KHO FDT description that will be superseded
by addition of KHO ABI documentation.

[rppt@kernel.org: fix Documentation/core-api/kho/index.rst]
  Link: https://lkml.kernel.org/r/aV4bnHlBXGpT_FMc@kernel.org
Link: https://lkml.kernel.org/r/20260105165839.285270-4-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Jason Miu <jasonmiu@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-26 19:07:11 -08:00
Pasha Tatashin
998be0a4db liveupdate: separate memfd support into LIVEUPDATE_MEMFD 
Decouple memfd preservation support from the core Live Update Orchestrator
configuration.

Previously, enabling CONFIG_LIVEUPDATE forced a dependency on CONFIG_SHMEM
and unconditionally compiled memfd_luo.o.  However, Live Update may be
used for purposes that do not require memfd-backed memory preservation.

Introduce CONFIG_LIVEUPDATE_MEMFD to gate memfd_luo.o.  This moves the
SHMEM and MEMFD_CREATE dependencies to the specific feature that needs
them, allowing the base LIVEUPDATE option to be selected independently of
shared memory support.

Link: https://lkml.kernel.org/r/20251230161402.1542099-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-01-26 19:07:10 -08:00