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
  ...

Author: torvalds

Documentation/ABI/testing/sysfs-kernel-mm-damon

@@ -316,6 +316,12 @@ Contact:	SeongJae Park <sj@kernel.org>
 Description:	Writing to and reading from this file sets and gets the path
 		parameter of the goal.
 
+What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/quotas/goal_tuner
+Date:		Mar 2026
+Contact:	SeongJae Park <sj@kernel.org>
+Description:	Writing to and reading from this file sets and gets the
+		goal-based effective quota auto-tuning algorithm to use.
+
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/quotas/weights/sz_permil
 Date:		Mar 2022
 Contact:	SeongJae Park <sj@kernel.org>

Documentation/admin-guide/blockdev/zram.rst

@@ -462,7 +462,7 @@ know it via /sys/block/zram0/bd_stat's 3rd column.
 recompression
 -------------
 
-With CONFIG_ZRAM_MULTI_COMP, zram can recompress pages using alternative
+With `CONFIG_ZRAM_MULTI_COMP`, zram can recompress pages using alternative
 (secondary) compression algorithms. The basic idea is that alternative
 compression algorithm can provide better compression ratio at a price of
 (potentially) slower compression/decompression speeds. Alternative compression
@@ -471,7 +471,7 @@ that default algorithm failed to compress). Another application is idle pages
 recompression - pages that are cold and sit in the memory can be recompressed
 using more effective algorithm and, hence, reduce zsmalloc memory usage.
 
-With CONFIG_ZRAM_MULTI_COMP, zram supports up to 4 compression algorithms:
+With `CONFIG_ZRAM_MULTI_COMP`, zram supports up to 4 compression algorithms:
 one primary and up to 3 secondary ones. Primary zram compressor is explained
 in "3) Select compression algorithm", secondary algorithms are configured
 using recomp_algorithm device attribute.
@@ -495,56 +495,43 @@ configuration:::
 	#select deflate recompression algorithm, priority 2
 	echo "algo=deflate priority=2" > /sys/block/zramX/recomp_algorithm
 
-Another device attribute that CONFIG_ZRAM_MULTI_COMP enables is recompress,
+Another device attribute that `CONFIG_ZRAM_MULTI_COMP` enables is `recompress`,
 which controls recompression.
 
 Examples:::
 
 	#IDLE pages recompression is activated by `idle` mode
-	echo "type=idle" > /sys/block/zramX/recompress
+	echo "type=idle priority=1" > /sys/block/zramX/recompress
 
 	#HUGE pages recompression is activated by `huge` mode
-	echo "type=huge" > /sys/block/zram0/recompress
+	echo "type=huge priority=2" > /sys/block/zram0/recompress
 
 	#HUGE_IDLE pages recompression is activated by `huge_idle` mode
-	echo "type=huge_idle" > /sys/block/zramX/recompress
+	echo "type=huge_idle priority=1" > /sys/block/zramX/recompress
 
 The number of idle pages can be significant, so user-space can pass a size
 threshold (in bytes) to the recompress knob: zram will recompress only pages
 of equal or greater size:::
 
 	#recompress all pages larger than 3000 bytes
-	echo "threshold=3000" > /sys/block/zramX/recompress
+	echo "threshold=3000 priority=1" > /sys/block/zramX/recompress
 
 	#recompress idle pages larger than 2000 bytes
-	echo "type=idle threshold=2000" > /sys/block/zramX/recompress
+	echo "type=idle threshold=2000 priority=1" > \
+		/sys/block/zramX/recompress
 
 It is also possible to limit the number of pages zram re-compression will
 attempt to recompress:::
 
-	echo "type=huge_idle max_pages=42" > /sys/block/zramX/recompress
-
-During re-compression for every page, that matches re-compression criteria,
-ZRAM iterates the list of registered alternative compression algorithms in
-order of their priorities. ZRAM stops either when re-compression was
-successful (re-compressed object is smaller in size than the original one)
-and matches re-compression criteria (e.g. size threshold) or when there are
-no secondary algorithms left to try. If none of the secondary algorithms can
-successfully re-compressed the page such a page is marked as incompressible,
-so ZRAM will not attempt to re-compress it in the future.
-
-This re-compression behaviour, when it iterates through the list of
-registered compression algorithms, increases our chances of finding the
-algorithm that successfully compresses a particular page. Sometimes, however,
-it is convenient (and sometimes even necessary) to limit recompression to
-only one particular algorithm so that it will not try any other algorithms.
-This can be achieved by providing a `algo` or `priority` parameter:::
-
-	#use zstd algorithm only (if registered)
-	echo "type=huge algo=zstd" > /sys/block/zramX/recompress
-
-	#use zstd algorithm only (if zstd was registered under priority 1)
-	echo "type=huge priority=1" > /sys/block/zramX/recompress
+	echo "type=huge_idle priority=1 max_pages=42" > \
+		/sys/block/zramX/recompress
+
+It is advised to always specify `priority` parameter.  While it is also
+possible to specify `algo` parameter, so that `zram` will use algorithm's
+name to determine the priority, it is not recommended, since it can lead to
+unexpected results when the same algorithm is configured with different
+priorities (e.g. different parameters).  `priority` is the only way to
+guarantee that the expected algorithm will be used.
 
 memory tracking
 ===============

Documentation/admin-guide/cgroup-v2.rst

@@ -1734,6 +1734,11 @@ The following nested keys are defined.
 	  zswpwb
 		Number of pages written from zswap to swap.
 
+	  zswap_incomp
+		Number of incompressible pages currently stored in zswap
+		without compression. These pages could not be compressed to
+		a size smaller than PAGE_SIZE, so they are stored as-is.
+
 	  thp_fault_alloc (npn)
 		Number of transparent hugepages which were allocated to satisfy
 		a page fault. This counter is not present when CONFIG_TRANSPARENT_HUGEPAGE

Documentation/admin-guide/kdump/vmcoreinfo.rst

@@ -141,7 +141,7 @@ nodemask_t
 The size of a nodemask_t type. Used to compute the number of online
 nodes.
 
-(page, flags|_refcount|mapping|lru|_mapcount|private|compound_order|compound_head)
+(page, flags|_refcount|mapping|lru|_mapcount|private|compound_order|compound_info)
 ----------------------------------------------------------------------------------
 
 User-space tools compute their values based on the offset of these

Documentation/admin-guide/kernel-parameters.txt

@@ -2970,6 +2970,12 @@ Kernel parameters
 			Format: <bool>
 			Default: CONFIG_KFENCE_DEFERRABLE
 
+	kfence.fault=	[MM,KFENCE] Controls the behavior when a KFENCE
+			error is detected.
+			report - print the error report and continue (default).
+			oops   - print the error report and oops.
+			panic  - print the error report and panic.
+
 	kfence.sample_interval=
 			[MM,KFENCE] KFENCE's sample interval in milliseconds.
 			Format: <unsigned integer>

Documentation/admin-guide/mm/damon/lru_sort.rst

@@ -91,8 +91,8 @@ increases and decreases the effective level of the quota aiming the LRU
 
 Disabled by default.
 
-Auto-tune monitoring intervals
-------------------------------
+autotune_monitoring_intervals
+-----------------------------
 
 If this parameter is set as ``Y``, DAMON_LRU_SORT automatically tunes DAMON's
 sampling and aggregation intervals.  The auto-tuning aims to capture meaningful
@@ -221,6 +221,10 @@ But, setting this too high could result in increased monitoring overhead.
 Please refer to the DAMON documentation (:doc:`usage`) for more detail.  10 by
 default.
 
+Note that this must be 3 or higher. Please refer to the :ref:`Monitoring
+<damon_design_monitoring>` section of the design document for the rationale
+behind this lower bound.
+
 max_nr_regions
 --------------
 
@@ -351,3 +355,8 @@ the LRU-list based page granularity reclamation. ::
     # echo 400 > wmarks_mid
     # echo 200 > wmarks_low
     # echo Y > enabled
+
+Note that this module (damon_lru_sort) cannot run simultaneously with other
+DAMON-based special-purpose modules.  Refer to :ref:`DAMON design special
+purpose modules exclusivity <damon_design_special_purpose_modules_exclusivity>`
+for more details.

Documentation/admin-guide/mm/damon/reclaim.rst

@@ -204,6 +204,10 @@ monitoring.  This can be used to set lower-bound of the monitoring quality.
 But, setting this too high could result in increased monitoring overhead.
 Please refer to the DAMON documentation (:doc:`usage`) for more detail.
 
+Note that this must be 3 or higher. Please refer to the :ref:`Monitoring
+<damon_design_monitoring>` section of the design document for the rationale
+behind this lower bound.
+
 max_nr_regions
 --------------
 
@@ -318,6 +322,11 @@ granularity reclamation. ::
     # echo 200 > wmarks_low
     # echo Y > enabled
 
+Note that this module (damon_reclaim) cannot run simultaneously with other
+DAMON-based special-purpose modules.  Refer to :ref:`DAMON design special
+purpose modules exclusivity <damon_design_special_purpose_modules_exclusivity>`
+for more details.
+
 .. [1] https://research.google/pubs/pub48551/
 .. [2] https://lwn.net/Articles/787611/
 .. [3] https://www.kernel.org/doc/html/latest/mm/free_page_reporting.html

Documentation/admin-guide/mm/damon/stat.rst

@@ -45,6 +45,11 @@ You can enable DAMON_STAT by setting the value of this parameter as ``Y``.
 Setting it as ``N`` disables DAMON_STAT.  The default value is set by
 ``CONFIG_DAMON_STAT_ENABLED_DEFAULT`` build config option.
 
+Note that this module (damon_stat) cannot run simultaneously with other
+DAMON-based special-purpose modules.  Refer to :ref:`DAMON design special
+purpose modules exclusivity <damon_design_special_purpose_modules_exclusivity>`
+for more details.
+
 .. _damon_stat_aggr_interval_us:
 
 aggr_interval_us

Documentation/admin-guide/mm/damon/usage.rst

@@ -83,7 +83,7 @@ comma (",").
     │ │ │ │ │ │ │ │ sz/min,max
     │ │ │ │ │ │ │ │ nr_accesses/min,max
     │ │ │ │ │ │ │ │ age/min,max
-    │ │ │ │ │ │ │ :ref:`quotas <sysfs_quotas>`/ms,bytes,reset_interval_ms,effective_bytes
+    │ │ │ │ │ │ │ :ref:`quotas <sysfs_quotas>`/ms,bytes,reset_interval_ms,effective_bytes,goal_tuner
     │ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
     │ │ │ │ │ │ │ │ :ref:`goals <sysfs_schemes_quota_goals>`/nr_goals
     │ │ │ │ │ │ │ │ │ 0/target_metric,target_value,current_value,nid,path
@@ -377,9 +377,9 @@ schemes/<N>/quotas/
 The directory for the :ref:`quotas <damon_design_damos_quotas>` of the given
 DAMON-based operation scheme.
 
-Under ``quotas`` directory, four files (``ms``, ``bytes``,
-``reset_interval_ms``, ``effective_bytes``) and two directories (``weights`` and
-``goals``) exist.
+Under ``quotas`` directory, five files (``ms``, ``bytes``,
+``reset_interval_ms``, ``effective_bytes`` and ``goal_tuner``) and two
+directories (``weights`` and ``goals``) exist.
 
 You can set the ``time quota`` in milliseconds, ``size quota`` in bytes, and
 ``reset interval`` in milliseconds by writing the values to the three files,
@@ -390,6 +390,14 @@ apply the action to only up to ``bytes`` bytes of memory regions within the
 quota limits unless at least one :ref:`goal <sysfs_schemes_quota_goals>` is
 set.
 
+You can set the goal-based effective quota auto-tuning algorithm to use, by
+writing the algorithm name to ``goal_tuner`` file.  Reading the file returns
+the currently selected tuner algorithm.  Refer to the design documentation of
+:ref:`automatic quota tuning goals <damon_design_damos_quotas_auto_tuning>` for
+the background design of the feature and the name of the selectable algorithms.
+Refer to :ref:`goals directory <sysfs_schemes_quota_goals>` for the goals
+setup.
+
 The time quota is internally transformed to a size quota.  Between the
 transformed size quota and user-specified size quota, smaller one is applied.
 Based on the user-specified :ref:`goal <sysfs_schemes_quota_goals>`, the

Documentation/admin-guide/mm/kho.rst

@@ -28,20 +28,10 @@ per NUMA node scratch regions on boot.
 Perform a KHO kexec
 ===================
 
-First, before you perform a KHO kexec, you need to move the system into
-the :ref:`KHO finalization phase <kho-finalization-phase>` ::
-
-  $ echo 1 > /sys/kernel/debug/kho/out/finalize
-
-After this command, the KHO FDT is available in
-``/sys/kernel/debug/kho/out/fdt``. Other subsystems may also register
-their own preserved sub FDTs under
-``/sys/kernel/debug/kho/out/sub_fdts/``.
-
-Next, load the target payload and kexec into it. It is important that you
-use the ``-s`` parameter to use the in-kernel kexec file loader, as user
-space kexec tooling currently has no support for KHO with the user space
-based file loader ::
+To perform a KHO kexec, load the target payload and kexec into it. It
+is important that you use the ``-s`` parameter to use the in-kernel
+kexec file loader, as user space kexec tooling currently has no
+support for KHO with the user space based file loader ::
 
   # kexec -l /path/to/bzImage --initrd /path/to/initrd -s
   # kexec -e
@@ -52,40 +42,19 @@ For example, if you used ``reserve_mem`` command line parameter to create
 an early memory reservation, the new kernel will have that memory at the
 same physical address as the old kernel.
 
-Abort a KHO exec
-================
-
-You can move the system out of KHO finalization phase again by calling ::
-
-  $ echo 0 > /sys/kernel/debug/kho/out/active
-
-After this command, the KHO FDT is no longer available in
-``/sys/kernel/debug/kho/out/fdt``.
-
 debugfs Interfaces
 ==================
 
+These debugfs interfaces are available when the kernel is compiled with
+``CONFIG_KEXEC_HANDOVER_DEBUGFS`` enabled.
+
 Currently KHO creates the following debugfs interfaces. Notice that these
 interfaces may change in the future. They will be moved to sysfs once KHO is
 stabilized.
 
-``/sys/kernel/debug/kho/out/finalize``
-    Kexec HandOver (KHO) allows Linux to transition the state of
-    compatible drivers into the next kexec'ed kernel. To do so,
-    device drivers will instruct KHO to preserve memory regions,
-    which could contain serialized kernel state.
-    While the state is serialized, they are unable to perform
-    any modifications to state that was serialized, such as
-    handed over memory allocations.
-
-    When this file contains "1", the system is in the transition
-    state. When contains "0", it is not. To switch between the
-    two states, echo the respective number into this file.
-
 ``/sys/kernel/debug/kho/out/fdt``
-    When KHO state tree is finalized, the kernel exposes the
-    flattened device tree blob that carries its current KHO
-    state in this file. Kexec user space tooling can use this
+    The kernel exposes the flattened device tree blob that carries its
+    current KHO state in this file. Kexec user space tooling can use this
     as input file for the KHO payload image.
 
 ``/sys/kernel/debug/kho/out/scratch_len``
@@ -100,8 +69,8 @@ stabilized.
     it should place its payload images.
 
 ``/sys/kernel/debug/kho/out/sub_fdts/``
-    In the KHO finalization phase, KHO producers register their own
-    FDT blob under this directory.
+    KHO producers can register their own FDT or another binary blob under
+    this directory.
 
 ``/sys/kernel/debug/kho/in/fdt``
     When the kernel was booted with Kexec HandOver (KHO),