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Author SHA1 Message Date
Hubert Mazur 1871d548fc mm/execmem: make the populate and alloc atomic 
When a block of memory is requested from the execmem manager it tries to
find a suitable fragment by traversing the free_areas.  In case there is
no such block, a new memory area is added to the free_areas and then
allocated to the caller by traversing the free_area tree again.

The above operations of allocation and tree traversal are not atomic hence
another request may consume this newly allocated memory block which
results in the allocation failure for the original request.  Such
occurrence can be spotted on devices running the 6.18 kernel during the
parallel modules loading.

To mitigate such resource races execute the cache population and
allocation operations under one mutex lock.

Link: https://lkml.kernel.org/r/20260320075723.779985-1-hmazur@google.com
Signed-off-by: Hubert Mazur <hmazur@google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Stanislaw Kardach <skardach@google.com>
Cc: Michal Krawczyk <mikrawczyk@google.com>
Cc: Slawomir Rosek <srosek@google.com>
Cc: Hubert Mazur <hmazur@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:34 -07:00
Liew Rui Yan 6f1e182387 Docs/mm/damon: document min_nr_regions constraint and rationale 
The current DAMON implementation requires 'min_nr_regions' to be at least
3.  However, this constraint is not explicitly documented in the
admin-guide documents, nor is its design rationale explained in the design
document.

Add a section in design.rst to explain the rationale: the virtual address
space monitoring design needs to handle at least three regions to
accommodate two large unmapped areas.  While this is specific to 'vaddr',
DAMON currently enforces it across all operation sets for consistency.

Also update reclaim.rst and lru_sort.rst by adding cross-references to
this constraint within their respective 'min_nr_regions' parameter
description sections, ensuring users are aware of the lower bound.

This change is motivated from a recent discussion [1].

Link: https://lkml.kernel.org/r/20260320052428.213230-1-aethernet65535@gmail.com
Link: https://lore.kernel.org/damon/20260319151528.86490-1-sj@kernel.org/T/#t [1]
Signed-off-by: Liew Rui Yan <aethernet65535@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:34 -07:00
Josh Law cc4555fc6d mm/damon/core: document damos_commit_dests() failure semantics 
Add a kernel-doc-like comment to damos_commit_dests() documenting its
allocation failure contract: on -ENOMEM, the destination structure is left
in a partially torn-down state that is safe to deallocate via
damon_destroy_scheme(), but must not be reused for further commits.

This was unclear from the code alone and led to a separate patch [1]
attempting to reset nr_dests on failure.  Make the intended usage explicit
so future readers do not repeat the confusion.

Link: https://lkml.kernel.org/r/20260320143648.91673-1-sj@kernel.org
Link: https://lore.kernel.org/20260318214939.36100-1-objecting@objecting.org [1]
Signed-off-by: Josh Law <objecting@objecting.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:34 -07:00
Leno Hou a6a8c087dc mm/mglru: fix cgroup OOM during MGLRU state switching 
When the Multi-Gen LRU (MGLRU) state is toggled dynamically, a race
condition exists between the state switching and the memory reclaim path. 
This can lead to unexpected cgroup OOM kills, even when plenty of
reclaimable memory is available.

Problem Description
==================
The issue arises from a "reclaim vacuum" during the transition.

1. When disabling MGLRU, lru_gen_change_state() sets lrugen->enabled to
   false before the pages are drained from MGLRU lists back to traditional
   LRU lists.
2. Concurrent reclaimers in shrink_lruvec() see lrugen->enabled as false
   and skip the MGLRU path.
3. However, these pages might not have reached the traditional LRU lists
   yet, or the changes are not yet visible to all CPUs due to a lack
   of synchronization.
4. get_scan_count() subsequently finds traditional LRU lists empty,
   concludes there is no reclaimable memory, and triggers an OOM kill.

A similar race can occur during enablement, where the reclaimer sees the
new state but the MGLRU lists haven't been populated via fill_evictable()
yet.

Solution
========
Introduce a 'switching' state (`lru_switch`) to bridge the transition.
When transitioning, the system enters this intermediate state where
the reclaimer is forced to attempt both MGLRU and traditional reclaim
paths sequentially. This ensures that folios remain visible to at least
one reclaim mechanism until the transition is fully materialized across
all CPUs.

Race & Mitigation
================
A race window exists between checking the 'draining' state and performing
the actual list operations. For instance, a reclaimer might observe the
draining state as false just before it changes, leading to a suboptimal
reclaim path decision.

However, this impact is effectively mitigated by the kernel's reclaim
retry mechanism (e.g., in do_try_to_free_pages). If a reclaimer pass fails
to find eligible folios due to a state transition race, subsequent retries
in the loop will observe the updated state and correctly direct the scan
to the appropriate LRU lists. This ensures the transient inconsistency
does not escalate into a terminal OOM kill.

This effectively reduce the race window that previously triggered OOMs
under high memory pressure.

This fix has been verified on v7.0.0-rc1; dynamic toggling of MGLRU
functions correctly without triggering unexpected OOM kills.

Link: https://lkml.kernel.org/r/20260319-b4-switch-mglru-v2-v5-1-8898491e5f17@gmail.com
Signed-off-by: Leno Hou <lenohou@gmail.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Jialing Wang <wjl.linux@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Bingfang Guo <bfguo@icloud.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:33 -07:00
teawater dc711106a0 zsmalloc: return -EBUSY for zspage migration lock contention 
movable_operations::migrate_page() should return an appropriate error code
for temporary migration failures so the migration core can handle them
correctly.

zs_page_migrate() currently returns -EINVAL when zspage_write_trylock()
fails.  That path reflects transient lock contention, not invalid input,
so -EINVAL is clearly wrong.

However, -EAGAIN is also inappropriate here: the zspage's reader-lock
owner may hold the lock for an unbounded duration due to slow
decompression or reader-lock owner preemption.  Since migration retries
are bounded by NR_MAX_MIGRATE_PAGES_RETRY and performed with virtually no
delay between attempts, there is no guarantee the lock will be released in
time for a retry to succeed.  -EAGAIN implies "try again soon", which does
not hold in this case.

Return -EBUSY instead, which more accurately conveys that the resource is
occupied and migration cannot proceed at this time.

Link: https://lkml.kernel.org/r/20260319065924.69337-1-hui.zhu@linux.dev
Signed-off-by: teawater <zhuhui@kylinos.cn>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:33 -07:00
David Hildenbrand (Arm) 6ebf98d71f mm: introduce CONFIG_NUMA_MIGRATION and simplify CONFIG_MIGRATION 
CONFIG_MEMORY_HOTREMOVE, CONFIG_COMPACTION and CONFIG_CMA all select
CONFIG_MIGRATION, because they require it to work (users).

Only CONFIG_NUMA_BALANCING and CONFIG_BALLOON_MIGRATION depend on
CONFIG_MIGRATION.  CONFIG_BALLOON_MIGRATION is not an actual user, but an
implementation of migration support, so the dependency is correct
(CONFIG_BALLOON_MIGRATION does not make any sense without
CONFIG_MIGRATION).

However, kconfig-language.rst clearly states "In general use select only
for non-visible symbols".  So far CONFIG_MIGRATION is user-visible ... 
and the dependencies rather confusing.

The whole reason why CONFIG_MIGRATION is user-visible is because of
CONFIG_NUMA: some users might want CONFIG_NUMA but not page migration
support.

Let's clean all that up by introducing a dedicated CONFIG_NUMA_MIGRATION
config option for that purpose only.  Make CONFIG_NUMA_BALANCING that so
far depended on CONFIG_NUMA && CONFIG_MIGRATION to depend on
CONFIG_MIGRATION instead.  CONFIG_NUMA_MIGRATION will depend on
CONFIG_NUMA && CONFIG_MMU.

CONFIG_NUMA_MIGRATION is user-visible and will default to "y".  We use
that default so new configs will automatically enable it, just like it was
the case with CONFIG_MIGRATION.  The downside is that some configs that
used to have CONFIG_MIGRATION=n might get it re-enabled by
CONFIG_NUMA_MIGRATION=y, which shouldn't be a problem.

CONFIG_MIGRATION is now a non-visible config option.  Any code that select
CONFIG_MIGRATION (as before) must depend directly or indirectly on
CONFIG_MMU.

CONFIG_NUMA_MIGRATION is responsible for any NUMA migration code, which is
mempolicy migration code, memory-tiering code, and move_pages() code in
migrate.c.  CONFIG_NUMA_BALANCING uses its functionality.

Note that this implies that with CONFIG_NUMA_MIGRATION=n, move_pages()
will not be available even though CONFIG_MIGRATION=y, which is an expected
change.

In migrate.c, we can remove the CONFIG_NUMA check as both
CONFIG_NUMA_MIGRATION and CONFIG_NUMA_BALANCING depend on it.

With this change, CONFIG_MIGRATION is an internal config, all users of
migration selects CONFIG_MIGRATION, and only CONFIG_BALLOON_MIGRATION
depends on it.

Link: https://lkml.kernel.org/r/20260319-config_migration-v1-2-42270124966f@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:33 -07:00
David Hildenbrand (Arm) 078f80f909 mm: remove CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE 
Patch series "mm: remove CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE and cleanup
CONFIG_MIGRATION".

While working on memory hotplug code cleanups, I realized that
CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE is not really required anymore.

Changing that revealed some rather nasty looking CONFIG_MIGRATION
handling.

Let's clean that up by introducing a dedicated CONFIG_NUMA_MIGRATION
option and reducing the dependencies that CONFIG_MIGRATION has.


This patch (of 2):

All architectures that select CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE also
select CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG.  So we can just remove
CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE.

For CONFIG_MIGRATION, make it depend on CONFIG_MEMORY_HOTREMOVE instead,
and make CONFIG_MEMORY_HOTREMOVE select CONFIG_MIGRATION (just like
CONFIG_CMA and CONFIG_COMPACTION already do).

We'll clean up CONFIG_MIGRATION next.

Link: https://lkml.kernel.org/r/20260319-config_migration-v1-0-42270124966f@kernel.org
Link: https://lkml.kernel.org/r/20260319-config_migration-v1-1-42270124966f@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:33 -07:00
David Hildenbrand (Arm) 738de20c4f mm/sparse: move memory hotplug bits to sparse-vmemmap.c 
Let's move all memory hoptplug related code to sparse-vmemmap.c.

We only have to expose sparse_index_init().  While at it, drop the
definition of sparse_index_init() for !CONFIG_SPARSEMEM, which is unused,
and place the declaration in internal.h.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-15-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:33 -07:00
David Hildenbrand (Arm) 08e5f77c37 mm/sparse: move __section_mark_present() to internal.h 
Let's prepare for moving memory hotplug handling from sparse.c to
sparse-vmemmap.c by moving __section_mark_present() to internal.h.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-14-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:33 -07:00
David Hildenbrand (Arm) f62a3bf227 mm/sparse: move sparse_init_one_section() to internal.h 
While at it, convert the BUG_ON to a VM_WARN_ON_ONCE, avoid long lines,
and merge sparse_encode_mem_map() into its only caller
sparse_init_one_section().

Clarify the comment a bit, pointing at page_to_pfn().

[david@kernel.org: s/VM_WARN_ON/VM_WARN_ON_ONCE/]
  Link: https://lkml.kernel.org/r/6b04c1a1-74e7-42e8-8523-a40802e5dacc@kernel.org
Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-13-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:33 -07:00
David Hildenbrand (Arm) b551ed94d9 mm/sparse: drop set_section_nid() from sparse_add_section() 
CONFIG_MEMORY_HOTPLUG is CONFIG_SPARSEMEM_VMEMMAP-only.  And
CONFIG_SPARSEMEM_VMEMMAP implies that NODE_NOT_IN_PAGE_FLAGS cannot be
set: see include/linux/page-flags-layout.h

	...
	#elif defined(CONFIG_SPARSEMEM_VMEMMAP)
	#error "Vmemmap: No space for nodes field in page flags"
	...

Which implies that the node is always stored in page flags and
NODE_NOT_IN_PAGE_FLAGS cannot be set.  Therefore, set_section_nid() is a
NOP on CONFIG_SPARSEMEM_VMEMMAP.

So let's remove the set_section_nid() call to prepare for moving
CONFIG_MEMORY_HOTPLUG to mm/sparse-vmemmap.c

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-12-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:32 -07:00
David Hildenbrand (Arm) fead6dcff8 mm: prepare to move subsection_map_init() to mm/sparse-vmemmap.c 
We want to move subsection_map_init() to mm/sparse-vmemmap.c.

To prepare for getting rid of subsection_map_init() in mm/sparse.c
completely, use a static inline function for !CONFIG_SPARSEMEM_VMEMMAP.

While at it, move the declaration to internal.h and rename it to
"sparse_init_subsection_map()".

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-11-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:32 -07:00
David Hildenbrand (Arm) dac89b150b mm/sparse: remove CONFIG_MEMORY_HOTPLUG-specific usemap allocation handling 
In 2008, we added through commit 48c906823f ("memory hotplug: allocate
usemap on the section with pgdat") quite some complexity to try allocating
memory for the "usemap" (storing pageblock information per memory section)
for a memory section close to the memory of the "pgdat" of the node.

The goal was to make memory hotunplug of boot memory more likely to
succeed.  That commit also added some checks for circular dependencies
between two memory sections, whereby two memory sections would contain
each others usemap, turning both boot memory sections un-removable.

However, in 2010, commit a4322e1bad ("sparsemem: Put usemap for one node
together") started allocating the usemap for multiple memory sections on
the same node in one chunk, effectively grouping all usemap allocations of
the same node in a single memblock allocation.

We don't really give guarantees about memory hotunplug of boot memory, and
with the change in 2010, it is impossible in practice to get any circular
dependencies.

So let's simply remove this complexity.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-10-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:32 -07:00
David Hildenbrand (Arm) 22688ade3b mm/sparse: remove sparse_decode_mem_map() 
section_deactivate() applies to CONFIG_SPARSEMEM_VMEMMAP only.  So we can
just use pfn_to_page() (after making sure we have the start PFN of the
section), and remove sparse_decode_mem_map().

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-9-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:32 -07:00
David Hildenbrand (Arm) 7f8e592bb3 mm/bootmem_info: avoid using sparse_decode_mem_map() 
With SPARSEMEM_VMEMMAP, we can just do a pfn_to_page().  It is not super
clear whether the start_pfn is properly aligned ...  so let's just make
sure it is properly aligned to the start of the section.

We will soon might try to remove the bootmem info completely, for now,
just keep it working as is.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-8-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:32 -07:00
David Hildenbrand (Arm) 4129341443 mm/bootmem_info: remove handling for !CONFIG_SPARSEMEM_VMEMMAP 
It is not immediately obvious that CONFIG_HAVE_BOOTMEM_INFO_NODE is only
selected from CONFIG_MEMORY_HOTREMOVE, which itself depends on
CONFIG_MEMORY_HOTPLUG that ...  depends on CONFIG_SPARSEMEM_VMEMMAP.

Let's remove the !CONFIG_SPARSEMEM_VMEMMAP leftovers that are dead code.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-7-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:32 -07:00
David Hildenbrand (Arm) 119c31caa5 mm/sparse: remove !CONFIG_SPARSEMEM_VMEMMAP leftovers for CONFIG_MEMORY_HOTPLUG 
CONFIG_MEMORY_HOTPLUG now depends on CONFIG_SPARSEMEM_VMEMMAP.  So let's
remove the !CONFIG_SPARSEMEM_VMEMMAP leftovers that are dead code.

Adjust the comment above fill_subsection_map() accordingly.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-6-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:32 -07:00
David Hildenbrand (Arm) 62257a5fb9 mm/memory_hotplug: simplify check_pfn_span() 
We now always have CONFIG_SPARSEMEM_VMEMMAP, so remove the dead code.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-5-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:31 -07:00
David Hildenbrand (Arm) fb3c3f5d27 mm/Kconfig: make CONFIG_MEMORY_HOTPLUG depend on CONFIG_SPARSEMEM_VMEMMAP 
Ever since commit f8f03eb5f0 ("mm: stop making SPARSEMEM_VMEMMAP
user-selectable"), an architecture that supports CONFIG_SPARSEMEM_VMEMMAP
(by selecting SPARSEMEM_VMEMMAP_ENABLE) can no longer enable
CONFIG_SPARSEMEM without CONFIG_SPARSEMEM_VMEMMAP.

Right now, CONFIG_MEMORY_HOTPLUG is guarded by CONFIG_SPARSEMEM.

However, CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG is only enabled by
* arm64: which selects SPARSEMEM_VMEMMAP_ENABLE
* loongarch: which selects SPARSEMEM_VMEMMAP_ENABLE
* powerpc (64bit): which selects SPARSEMEM_VMEMMAP_ENABLE
* riscv (64bit): which selects SPARSEMEM_VMEMMAP_ENABLE
* s390 with SPARSEMEM: which selects SPARSEMEM_VMEMMAP_ENABLE
* x86 (64bit): which selects SPARSEMEM_VMEMMAP_ENABLE

So, we can make CONFIG_MEMORY_HOTPLUG depend on CONFIG_SPARSEMEM_VMEMMAP
without affecting any setups.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-4-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:31 -07:00
David Hildenbrand (Arm) e66383b674 mm/sparse: remove WARN_ONs from (online|offline)_mem_sections() 
We do not allow offlining of memory with memory holes, and always hotplug
memory without holes.

Consequently, we cannot end up onlining or offlining memory sections that
have holes (including invalid sections).  That's also why these WARN_ONs
never fired.

Let's remove the WARN_ONs along with the TODO regarding double-checking.
Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-3-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:31 -07:00
David Hildenbrand (Arm) 9d80de66a0 mm/memory_hotplug: remove for_each_valid_pfn() usage 
When offlining memory, we know that the memory range has no holes. 
Checking for valid pfns is not required.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-2-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:31 -07:00
David Hildenbrand (Arm) 89e69c7d18 mm/memory_hotplug: fix possible race in scan_movable_pages() 
Patch series "mm: memory hot(un)plug and SPARSEMEM cleanups", v2.

Some cleanups around memory hot(un)plug and SPARSEMEM.  In essence, we can
limit CONFIG_MEMORY_HOTPLUG to CONFIG_SPARSEMEM_VMEMMAP, remove some dead
code, and move all the hotplug bits over to mm/sparse-vmemmap.c.

Some further/related cleanups around other unnecessary code (memory hole
handling and complicated usemap allocation).

I have some further sparse.c cleanups lying around, and I'm planning on
getting rid of bootmem_info.c entirely.


This patch (of 15):

If a hugetlb folio gets freed while we are in scan_movable_pages(),
folio_nr_pages() could return 0, resulting in or'ing "0 - 1 = -1" to the
PFN, resulting in PFN = -1.  We're not holding any locks or references
that would prevent that.

for_each_valid_pfn() would then search for the next valid PFN, and could
return a PFN that is outside of the range of the original requested range.
do_migrate_page() would then try to migrate quite a big range, which is
certainly undesirable.

To fix it, simply test for valid folio_nr_pages() values.  While at it, as
PageHuge() really just does a page_folio() internally, we can just use
folio_test_hugetlb() on the folio directly.

scan_movable_pages() is expected to be fast, and we try to avoid taking
locks or grabbing references.  We cannot use folio_try_get() as that does
not work for free hugetlb folios.  We could grab the hugetlb_lock, but
that just adds complexity.

The race is unlikely to trigger in practice, so we won't be CCing stable.

Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-0-096addc8800d@kernel.org
Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-1-096addc8800d@kernel.org
Fixes: 16540dae95 ("mm/hugetlb: mm/memory_hotplug: use a folio in scan_movable_pages()")
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:31 -07:00
Chen Ni 42561b341b mm/swapfile: remove duplicate include of swap_table.h 
Remove duplicate inclusion of swap_table.h in swapfile.c to clean up
redundant code.

Link: https://lkml.kernel.org/r/20260318043849.399266-1-nichen@iscas.ac.cn
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:31 -07:00
Asier Gutierrez 01494f713e Docs/mm/damon/design: document DAMON actions when TRANSPARENT_HUGEPAGE is off 
MADV_HUGEPAGE and MADV_NOHUGEPAGE are guarded and they are not available
when compiling the kernel without TRANSPARENT_HUGEPAGE option.  The DAMON
behaviour is to silently fail [1] in when DAMOS_HUGEPAGE or
DAMOS_NOHUGEPAGE are used, but TRANSPARENT_HUGEPAGE is disabled.  Update
the DAMON documentation to reflect this behaviour.

Link: https://lkml.kernel.org/r/20260318035349.88715-1-sj@kernel.org
Link: https://lore.kernel.org/66131775-180b-4b9f-b7ce-61a3e077b6e6@huawei-partners.com/ [1]
Signed-off-by: Asier Gutierrez <gutierrez.asier@huawei-partners.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:31 -07:00
Sergey Senozhatsky cba8299330 zram: change scan_slots to return void 
scan_slots_for_writeback() and scan_slots_for_recompress() work in a "best
effort" fashion, if they cannot allocate memory for a new pp-slot
candidate they just return and post-processing selects slots that were
successfully scanned thus far.  scan_slots functions never return errors
and their callers never check the return status, so convert them to return
void.

Link: https://lkml.kernel.org/r/20260317032349.753645-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:30 -07:00
Liew Rui Yan 4bdbddb4e4 Docs/mm/damon: document exclusivity of special-purpose modules 
Add a section in design.rst to explain that DAMON special-purpose kernel
modules (LRU_SORT, RECLAIM, STAT) run in an exclusive manner and return
-EBUSY if another is already running.

Update lru_sort.rst, reclaim.rst and stat.rst by adding cross-references
to this exclusivity rule at the end of their respective Example sections.

This change is motivated from another discussion [1].

Link: https://lkml.kernel.org/r/20260315162945.80994-1-sj@kernel.org
Link: https://lore.kernel.org/damon/20260314002119.79742-1-sj@kernel.org/T/#t [1]
Signed-off-by: Liew Rui Yan <aethernet65535@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@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>
 2026-04-05 13:53:30 -07:00
Sergey Senozhatsky bf989ade27 zram: propagate read_from_bdev_async() errors 
When read_from_bdev_async() fails to chain bio, for instance fails to
allocate request or bio, we need to propagate the error condition so that
upper layer is aware of it.  zram already does that by setting
BLK_STS_IOERR ->bi_status, but only for sync reads.  Change async read
path to return its error status so that async errors are also handled.

Link: https://lkml.kernel.org/r/20260316015354.114465-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Suggested-by: Brian Geffon <bgeffon@google.com>
Acked-by: Brian Geffon <bgeffon@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Richard Chang <richardycc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:30 -07:00
gao xu f0f6f78714 zram: optimize LZ4 dictionary compression performance 
Calling `LZ4_loadDict()` repeatedly in Zram causes significant overhead
due to its internal dictionary pre-processing.  This commit introduces a
template stream mechanism to pre-process the dictionary only once when the
dictionary is initially set or modified.  It then efficiently copies this
state for subsequent compressions.

Verification Test Items:
Test Platform: android16-6.12
1. Collect Anonymous Page Dataset
1) Apply the following patch:
static bool zram_meta_alloc(struct zram *zram, u64 disksize)
	if (!huge_class_size)
-		huge_class_size = zs_huge_class_size(zram->mem_pool);
+		huge_class_size = 0;

2）Install multiple apps and monkey testing until SwapFree is close to 0.

3）Execute the following command to export data:
dd if=/dev/block/zram0 of=/data/samples/zram_dump.img bs=4K

2. Train Dictionary
Since LZ4 does not have a dedicated dictionary training tool, the zstd
tool can be used for training[1]. The command is as follows:
zstd --train /data/samples/* --split=4096 --maxdict=64KB -o /vendor/etc/dict_data

3. Test Code
adb shell "dd if=/data/samples/zram_dump.img of=/dev/test_pattern bs=4096 count=131072 conv=fsync"
adb shell "swapoff /dev/block/zram0"
adb shell "echo 1 > /sys/block/zram0/reset"
adb shell "echo lz4 > /sys/block/zram0/comp_algorithm"
adb shell "echo dict=/vendor/etc/dict_data   >  /sys/block/zram0/algorithm_params"
adb shell "echo 6G > /sys/block/zram0/disksize"
echo "Start Compression"
adb shell "taskset 80 dd if=/dev/test_pattern of=/dev/block/zram0 bs=4096 count=131072 conv=fsync"
echo.
echo "Start Decompression"
adb shell "taskset 80 dd if=/dev/block/zram0 of=/dev/output_result bs=4096 count=131072 conv=fsync"
echo "mm_stat:"
adb shell "cat /sys/block/zram0/mm_stat"
echo.
Note: To ensure stable test results, it is best to lock the CPU frequency
before executing the test.

LZ4 supports dictionaries up to 64KB. Below are the test results for
compression rates at various dictionary sizes:
dict_size          base        patch
  4 KB          156M/s      219M/s
  8 KB          136M/s      217M/s
 16KB           98M/s       214M/s
 32KB           66M/s       225M/s
 64KB           38M/s       224M/s

When an LZ4 compression dictionary is enabled, compression speed is
negatively impacted by the dictionary's size; larger dictionaries result
in slower compression.  This patch eliminates the influence of dictionary
size on compression speed, ensuring consistent performance regardless of
dictionary scale.

Link: https://lkml.kernel.org/r/698181478c9c4b10aa21b4a847bdc706@honor.com
Link: https://github.com/lz4/lz4?tab=readme-ov-file [1]
Signed-off-by: gao xu <gaoxu2@honor.com>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:30 -07:00
Nico Pache a155d945b7 mm/khugepaged: unify khugepaged and madv_collapse with collapse_single_pmd() 
The khugepaged daemon and madvise_collapse have two different
implementations that do almost the same thing.  Create collapse_single_pmd
to increase code reuse and create an entry point to these two users.

Refactor madvise_collapse and collapse_scan_mm_slot to use the new
collapse_single_pmd function.  To help reduce confusion around the
mmap_locked variable, we rename mmap_locked to lock_dropped in the
collapse_scan_mm_slot() function, and remove the redundant mmap_locked in
madvise_collapse(); this further unifies the code readiblity.  the
SCAN_PTE_MAPPED_HUGEPAGE enum is no longer reachable in the
madvise_collapse() function, so we drop it from the list of "continuing"
enums.

This introduces a minor behavioral change that is most likely an
undiscovered bug.  The current implementation of khugepaged tests
collapse_test_exit_or_disable() before calling collapse_pte_mapped_thp,
but we weren't doing it in the madvise_collapse case.  By unifying these
two callers madvise_collapse now also performs this check.  We also modify
the return value to be SCAN_ANY_PROCESS which properly indicates that this
process is no longer valid to operate on.

By moving the madvise_collapse writeback-retry logic into the helper
function we can also avoid having to revalidate the VMA.

We guard the khugepaged_pages_collapsed variable to ensure its only
incremented for khugepaged.

As requested we also convert a VM_BUG_ON to a VM_WARN_ON.

Link: https://lkml.kernel.org/r/20260325114022.444081-6-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:30 -07:00
Nico Pache ff7e03a871 mm/khugepaged: rename hpage_collapse_* to collapse_* 
The hpage_collapse functions describe functions used by madvise_collapse
and khugepaged.  remove the unnecessary hpage prefix to shorten the
function name.

Link: https://lkml.kernel.org/r/20260325114022.444081-5-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:30 -07:00
Nico Pache 36da8a88fd mm/khugepaged: define KHUGEPAGED_MAX_PTES_LIMIT as HPAGE_PMD_NR - 1 
The value (HPAGE_PMD_NR - 1) is used often in the khugepaged code to
signify the limit of the max_ptes_* values.  Add a define for this to
increase code readability and reuse.

Link: https://lkml.kernel.org/r/20260325114022.444081-4-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Acked-by: Pedro Falcato <pfalcato@suse.de>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Suggested-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:30 -07:00
Nico Pache b90c453d26 mm: introduce is_pmd_order helper 
In order to add mTHP support to khugepaged, we will often be checking if a
given order is (or is not) a PMD order.  Some places in the kernel already
use this check, so lets create a simple helper function to keep the code
clean and readable.

Link: https://lkml.kernel.org/r/20260325114022.444081-3-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:29 -07:00
Nico Pache a91fd9f710 mm: consolidate anonymous folio PTE mapping into helpers 
Patch series "mm: khugepaged cleanups and mTHP prerequisites", v4.

The following series contains cleanups and prerequisites for my work on
khugepaged mTHP support [1].  These have been separated out to ease
review.

The first patch in the series refactors the page fault folio to pte
mapping and follows a similar convention as defined by
map_anon_folio_pmd_(no)pf().  This not only cleans up the current
implementation of do_anonymous_page(), but will allow for reuse later in
the khugepaged mTHP implementation.

The second patch adds a small is_pmd_order() helper to check if an order
is the PMD order.  This check is open-coded in a number of places.  This
patch aims to clean this up and will be used more in the khugepaged mTHP
work.  The third patch also adds a small DEFINE for (HPAGE_PMD_NR - 1)
which is used often across the khugepaged code.

The fourth and fifth patch come from the khugepaged mTHP patchset [1]. 
These two patches include the rename of function prefixes, and the
unification of khugepaged and madvise_collapse via a new
collapse_single_pmd function.

Patch 1:     refactor do_anonymous_page into map_anon_folio_pte_(no)pf
Patch 2:     add is_pmd_order helper
Patch 3:     Add define for (HPAGE_PMD_NR - 1)
Patch 4:     Refactor/rename hpage_collapse
Patch 5:     Refactoring to combine madvise_collapse and khugepaged

A big thanks to everyone that has reviewed, tested, and participated in
the development process.


This patch (of 5):

The anonymous page fault handler in do_anonymous_page() open-codes the
sequence to map a newly allocated anonymous folio at the PTE level:

	- construct the PTE entry
	- add rmap
	- add to LRU
	- set the PTEs
	- update the MMU cache.

Introduce two helpers to consolidate this duplicated logic, mirroring the
existing map_anon_folio_pmd_nopf() pattern for PMD-level mappings:

map_anon_folio_pte_nopf(): constructs the PTE entry, takes folio
references, adds anon rmap and LRU.  This function also handles the
uffd_wp that can occur in the pf variant.  The future khugepaged mTHP code
calls this to handle mapping the new collapsed mTHP to its folio.

map_anon_folio_pte_pf(): extends the nopf variant to handle MM_ANONPAGES
counter updates, and mTHP fault allocation statistics for the page fault
path.

The zero-page read path in do_anonymous_page() is also untangled from the
shared setpte label, since it does not allocate a folio and should not
share the same mapping sequence as the write path.  We can now leave
nr_pages undeclared at the function intialization, and use the single page
update_mmu_cache function to handle the zero page update.

This refactoring will also help reduce code duplication between
mm/memory.c and mm/khugepaged.c, and provides a clean API for PTE-level
anonymous folio mapping that can be reused by future callers (like
khugpeaged mTHP support)

Link: https://lkml.kernel.org/r/20260325114022.444081-1-npache@redhat.com
Link: https://lkml.kernel.org/r/20260325114022.444081-2-npache@redhat.com
Link: https://lore.kernel.org/all/20260122192841.128719-1-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Suggested-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:29 -07:00
Jianhui Zhou 0217c7fb4d mm/userfaultfd: fix hugetlb fault mutex hash calculation 
In mfill_atomic_hugetlb(), linear_page_index() is used to calculate the
page index for hugetlb_fault_mutex_hash().  However, linear_page_index()
returns the index in PAGE_SIZE units, while hugetlb_fault_mutex_hash()
expects the index in huge page units.  This mismatch means that different
addresses within the same huge page can produce different hash values,
leading to the use of different mutexes for the same huge page.  This can
cause races between faulting threads, which can corrupt the reservation
map and trigger the BUG_ON in resv_map_release().

Fix this by introducing hugetlb_linear_page_index(), which returns the
page index in huge page granularity, and using it in place of
linear_page_index().

Link: https://lkml.kernel.org/r/20260310110526.335749-1-jianhuizzzzz@gmail.com
Fixes: a08c7193e4 ("mm/filemap: remove hugetlb special casing in filemap.c")
Signed-off-by: Jianhui Zhou <jianhuizzzzz@gmail.com>
Reported-by: syzbot+f525fd79634858f478e7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f525fd79634858f478e7
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: JonasZhou <JonasZhou@zhaoxin.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:29 -07:00
SeongJae Park 8c6a765f4a mm/damon/lru_sort: respect addr_unit on default monitoring region setup 
In the past, damon_set_region_biggest_system_ram_default(), which is the
core function for setting the default monitoring target region of
DAMON_LRU_SORT, didn't support addr_unit.  Hence DAMON_LRU_SORT was
silently ignoring the user input for addr_unit when the user doesn't
explicitly set the monitoring target regions, and therefore the default
target region is being used.  No real problem from that ignorance was
reported so far.  But, the implicit rule is only making things confusing. 
Also, the default target region setup function is updated to support
addr_unit.  Hence there is no reason to keep ignoring it.  Respect the
user-passed addr_unit for the default target monitoring region use case.

Link: https://lkml.kernel.org/r/20260311052927.93921-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Yang yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:29 -07:00
SeongJae Park fdfcda8d08 mm/damon/reclaim: respect addr_unit on default monitoring region setup 
In the past, damon_set_region_biggest_system_ram_default(), which is the
core function for setting the default monitoring target region of
DAMON_RECLAIM, didn't support addr_unit.  Hence DAMON_RECLAIM was silently
ignoring the user input for addr_unit when the user doesn't explicitly set
the monitoring target regions, and therefore the default target region is
being used.  No real problem from that ignorance was reported so far. 
But, the implicit rule is only making things confusing.  Also, the default
target region setup function is updated to support addr_unit.  Hence there
is no reason to keep ignoring it.  Respect the user-passed addr_unit for
the default target monitoring region use case.

Link: https://lkml.kernel.org/r/20260311052927.93921-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Yang yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:29 -07:00
SeongJae Park 5f9a5926b7 mm/damon/core: fix wrong damon_set_regions() argument 
The third argument is the length of the second parameter.  But addr_unit
is wrongly being passed.  Fix it.

Link: https://lkml.kernel.org/r/20260314001854.79623-1-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Yang yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:29 -07:00
SeongJae Park eabc2eddb2 mm/damon/core: receive addr_unit on damon_set_region_biggest_system_ram_default() 
damon_find_biggest_system_ram() was not supporting addr_unit in the past. 
Hence, its caller, damon_set_region_biggest_system_ram_default(), was also
not supporting addr_unit.  The previous commit has updated the inner
function to support addr_unit.  There is no more reason to not support
addr_unit on damon_set_region_biggest_system_ram_default().  Rather, it
makes unnecessary inconsistency on support of addr_unit.  Update it to
receive addr_unit and handle it inside.

Link: https://lkml.kernel.org/r/20260311052927.93921-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Yang yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:28 -07:00
SeongJae Park b47dcc1a28 mm/damon/core: support addr_unit on damon_find_biggest_system_ram() 
damon_find_biggest_system_ram() sets an 'unsigned long' variable with
'resource_size_t' value.  This is fundamentally wrong.  On environments
such as ARM 32 bit machines having LPAE (Large Physical Address
Extensions), which DAMON supports, the size of 'unsigned long' may be
smaller than that of 'resource_size_t'.  It is safe, though, since we
restrict the walk to be done only up to ULONG_MAX.

DAMON supports the address size gap using 'addr_unit'.  We didn't add the
support to the function, just to make the initial support change small. 
Now the support is reasonably settled.  This kind of gap is only making
the code inconsistent and easy to be confused.  Add the support of
'addr_unit' to the function, by letting callers pass the 'addr_unit' and
handling it in the function.  All callers are passing 'addr_unit' 1,
though, to keep the old behavior.

[sj@kernel.org: verify found biggest system ram]
  Link: https://lkml.kernel.org/r/20260317144725.88524-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20260311052927.93921-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Yang yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:28 -07:00
SeongJae Park c63067e8b0 mm/damon/core: fix wrong end address assignment on walk_system_ram() 
Patch series "mm/damon: support addr_unit on default monitoring targets
for modules".

DAMON_RECLAIM and DAMON_LRU_SORT support 'addr_unit' parameters only when
the monitoring target address range is explicitly set.  This was
intentional for making the initial 'addr_unit' support change small.  Now
'addr_unit' support is being quite stabilized.  Having the corner case of
the support is only making the code inconsistent with implicit rules.  The
inconsistency makes it easy to confuse [1] readers.  After all, there is
no real reason to keep 'addr_unit' support incomplete.  Add the support
for the case to improve the readability and more completely support
'addr_unit'.

This series is constructed with five patches.  The first one (patch 1)
fixes a small bug that mistakenly assigns inclusive end address to open
end address, which was found from this work.  The second and third ones
(patches 2 and 3) extend the default monitoring target setting functions
in the core layer one by one, to support the 'addr_unit' while making no
visible changes.  The final two patches (patches 4 and 5) update
DAMON_RECLAIM and DAMON_LRU_SORT to support 'addr_unit' for the default
monitoring target address ranges, by passing the user input to the core
functions.


This patch (of 5):

'struct damon_addr_range' and 'struct resource' represent different types
of address ranges.  'damon_addr_range' is for end-open ranges ([start,
end)).  'resource' is for fully-closed ranges ([start, end]).  But
walk_system_ram() is assigning resource->end to damon_addr_range->end
without the inclusiveness adjustment.  As a result, the function returns
an address range that is missing the last one byte.

The function is being used to find and set the biggest system ram as the
default monitoring target for DAMON_RECLAIM and DAMON_LRU_SORT.  Missing
the last byte of the big range shouldn't be a real problem for the real
use cases.  That said, the loss is definitely an unintended behavior.  Do
the correct adjustment.

Link: https://lkml.kernel.org/r/20260311052927.93921-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20260311052927.93921-2-sj@kernel.org
Link: https://lore.kernel.org/20260131015643.79158-1-sj@kernel.org [1]
Fixes: 43b0536cb4 ("mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Yang yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:28 -07:00
Lorenzo Stoakes (Oracle) 0289955fc5 mm/mremap: check map count under mmap write lock and abstract 
We are checking the mmap count in check_mremap_params(), prior to
obtaining an mmap write lock, which means that accesses to
current->mm->map_count might race with this field being updated.

Resolve this by only checking this field after the mmap write lock is held.

Additionally, abstract this check into a helper function with extensive
ASCII documentation of what's going on.

Link: https://lkml.kernel.org/r/18be0b48eaa8e8804eb745974ee729c3ade0c687.1773249037.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reported-by: Jianzhou Zhao <luckd0g@163.com>
Closes: https://lore.kernel.org/all/1a7d4c26.6b46.19cdbe7eaf0.Coremail.luckd0g@163.com/
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:28 -07:00
Lorenzo Stoakes (Oracle) 2d1e54aab6 mm: abstract reading sysctl_max_map_count, and READ_ONCE() 
Concurrent reads and writes of sysctl_max_map_count are possible, so we
should READ_ONCE() and WRITE_ONCE().

The sysctl procfs logic already enforces WRITE_ONCE(), so abstract the
read side with get_sysctl_max_map_count().

While we're here, also move the field to mm/internal.h and add the getter
there since only mm interacts with it, there's no need for anybody else to
have access.

Finally, update the VMA userland tests to reflect the change.

Link: https://lkml.kernel.org/r/0715259eb37cbdfde4f9e5db92a20ec7110a1ce5.1773249037.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: Jann Horn <jannh@google.com>
Cc: Jianzhou Zhao <luckd0g@163.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:28 -07:00
Lorenzo Stoakes (Oracle) 9b9b8d4aeb mm/mremap: correct invalid map count check 
Patch series "mm: improve map count checks".

Firstly, in mremap(), it appears that our map count checks have been overly
conservative - there is simply no reason to require that we have headroom
of 4 mappings prior to moving the VMA, we only need headroom of 2 VMAs
since commit 659ace584e ("mmap: don't return ENOMEM when mapcount is
temporarily exceeded in munmap()").

Likely the original headroom of 4 mappings was a mistake, and 3 was
actually intended.

Next, we access sysctl_max_map_count in a number of places without being
all that careful about how we do so.

We introduce a simple helper that READ_ONCE()'s the field
(get_sysctl_max_map_count()) to ensure that the field is accessed
correctly.  The WRITE_ONCE() side is already handled by the sysctl procfs
code in proc_int_conv().

We also move this field to internal.h as there's no reason for anybody
else to access it outside of mm.  Unfortunately we have to maintain the
extern variable, as mmap.c implements the procfs code.

Finally, we are accessing current->mm->map_count without holding the mmap
write lock, which is also not correct, so this series ensures the lock is
head before we access it.

We also abstract the check to a helper function, and add ASCII diagrams to
explain why we're doing what we're doing.


This patch (of 3):

We currently check to see, if on moving a VMA when doing mremap(), if it
might violate the sys.vm.max_map_count limit.

This was introduced in the mists of time prior to 2.6.12.

At this point in time, as now, the move_vma() operation would copy the VMA
(+1 mapping if not merged), then potentially split the source VMA upon
unmap.

Prior to commit 659ace584e ("mmap: don't return ENOMEM when mapcount is
temporarily exceeded in munmap()"), a VMA split would check whether
mm->map_count >= sysctl_max_map_count prior to a split before it ran.

On unmap of the source VMA, if we are moving a partial VMA, we might split
the VMA twice.

This would mean, on invocation of split_vma() (as was), we'd check whether
mm->map_count >= sysctl_max_map_count with a map count elevated by one,
then again with a map count elevated by two, ending up with a map count
elevated by three.

At this point we'd reduce the map count on unmap.

At the start of move_vma(), there was a check that has remained throughout
mremap()'s history of mm->map_count >= sysctl_max_map_count - 3 (which
implies mm->mmap_count + 4 > sysctl_max_map_count - that is, we must have
headroom for 4 additional mappings).

After mm->map_count is elevated by 3, it is decremented by one once the
unmap completes. The mmap write lock is held, so nothing else will observe
mm->map_count > sysctl_max_map_count.

It appears this check was always incorrect - it should have either be one
of 'mm->map_count > sysctl_max_map_count - 3' or 'mm->map_count >=
sysctl_max_map_count - 2'.

After commit 659ace584e ("mmap: don't return ENOMEM when mapcount is
temporarily exceeded in munmap()"), the map count check on split is
eliminated in the newly introduced __split_vma(), which the unmap path
uses, and has that path check whether mm->map_count >=
sysctl_max_map_count.

This is valid since, net, an unmap can only cause an increase in map count
of 1 (split both sides, unmap middle).

Since we only copy a VMA and (if MREMAP_DONTUNMAP is not set) unmap
afterwards, the maximum number of additional mappings that will actually be
subject to any check will be 2.

Therefore, update the check to assert this corrected value. Additionally,
update the check introduced by commit ea2c3f6f55 ("mm,mremap: bail out
earlier in mremap_to under map pressure") to account for this.

While we're here, clean up the comment prior to that.

Link: https://lkml.kernel.org/r/cover.1773249037.git.ljs@kernel.org
Link: https://lkml.kernel.org/r/73e218c67dcd197c5331840fb011e2c17155bfb0.1773249037.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jianzhou Zhao <luckd0g@163.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:28 -07:00
Kexin Sun d4e981b280 kasan: update outdated comment 
kmalloc_large() was renamed kmalloc_large_noprof() by commit 7bd230a266
("mm/slab: enable slab allocation tagging for kmalloc and friends"), and
subsequently renamed __kmalloc_large_noprof() by commit a0a44d9175 ("mm,
slab: don't wrap internal functions with alloc_hooks()"), making it an
internal implementation detail.

Large kmalloc allocations are now performed through the public kmalloc()
interface directly, making the reference to KMALLOC_MAX_SIZE also stale
(KMALLOC_MAX_CACHE_SIZE would be more accurate).  Remove the references to
kmalloc_large() and KMALLOC_MAX_SIZE, and rephrase the description for
large kmalloc allocations.

Link: https://lkml.kernel.org/r/20260312053812.1365-1-kexinsun@smail.nju.edu.cn
Signed-off-by: Kexin Sun <kexinsun@smail.nju.edu.cn>
Suggested-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Assisted-by: unnamed:deepseek-v3.2 coccinelle
Reviewed-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Julia Lawall <julia.lawall@inria.fr>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:28 -07:00
Usama Arif a2e0c0668a mm: migrate: requeue destination folio on deferred split queue 
During folio migration, __folio_migrate_mapping() removes the source folio
from the deferred split queue, but the destination folio is never
re-queued.  This causes underutilized THPs to escape the shrinker after
NUMA migration, since they silently drop off the deferred split list.

Fix this by recording whether the source folio was on the deferred split
queue and its partially mapped state before move_to_new_folio() unqueues
it, and re-queuing the destination folio after a successful migration if
it was.

By the time migrate_folio_move() runs, partially mapped folios without a
pin have already been split by migrate_pages_batch().  So only two cases
remain on the deferred list at this point:
  1. Partially mapped folios with a pin (split failed).
  2. Fully mapped but potentially underused folios.  The recorded
     partially_mapped state is forwarded to deferred_split_folio() so that
     the destination folio is correctly re-queued in both cases.

Because THPs are removed from the deferred_list, THP shinker cannot
split the underutilized THPs in time.  As a result, users will show
less free memory than before.  

Link: https://lkml.kernel.org/r/20260312104723.1351321-1-usama.arif@linux.dev
Fixes: dafff3f4c8 ("mm: split underused THPs")
Signed-off-by: Usama Arif <usama.arif@linux.dev>
Reported-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Ying Huang <ying.huang@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:27 -07:00
Waiman Long 2d028f3e4b selftest: memcg: skip memcg_sock test if address family not supported 
The test_memcg_sock test in memcontrol.c sets up an IPv6 socket and send
data over it to consume memory and verify that memory.stat.sock and
memory.current values are close.

On systems where IPv6 isn't enabled or not configured to support
SOCK_STREAM, the test_memcg_sock test always fails.  When the socket()
call fails, there is no way we can test the memory consumption and verify
the above claim.  I believe it is better to just skip the test in this
case instead of reporting a test failure hinting that there may be
something wrong with the memcg code.

Link: https://lkml.kernel.org/r/20260311200526.885899-1-longman@redhat.com
Fixes: 5f8f019380 ("selftests: cgroup/memcontrol: add basic test for socket accounting")
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:27 -07:00
Mike Rapoport (Microsoft) f08f610ea0 selftests/mm: pagemap_ioctl: remove hungarian notation 
Replace lpBaseAddress with addr and dwRegionSize with size.

Link: https://lkml.kernel.org/r/20260311180737.3767545-1-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:27 -07:00
Breno Leitao 3203a8706e mm: ratelimit min_free_kbytes adjustment messages 
The "raising min_free_kbytes" pr_info message in
set_recommended_min_free_kbytes() and the "min_free_kbytes is not updated
to" pr_warn in calculate_min_free_kbytes() can spam the kernel log when
called repeatedly.

Switch the pr_info in set_recommended_min_free_kbytes() and the pr_warn in
calculate_min_free_kbytes() to their _ratelimited variants to prevent the
log spam for this message.

Link: https://lkml.kernel.org/r/20260317-thp_logs-v7-4-31eb98fa5a8b@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:27 -07:00
Breno Leitao 35a01d9442 mm: huge_memory: refactor enabled_store() with set_global_enabled_mode() 
Refactor enabled_store() to use a new set_global_enabled_mode() helper. 
Introduce a separate enum global_enabled_mode and
global_enabled_mode_strings[], mirroring the anon_enabled_mode pattern
from the previous commit.

A separate enum is necessary because the global THP setting does not
support "inherit", only "always", "madvise", and "never".  Reusing
anon_enabled_mode would leave a NULL gap in the string array, causing
sysfs_match_string() to stop early and fail to match entries after the
gap.

The helper uses the same loop pattern as set_anon_enabled_mode(),
iterating over an array of flag bit positions and using
test_and_set_bit()/test_and_clear_bit() to track whether the state
actually changed.

Link: https://lkml.kernel.org/r/20260317-thp_logs-v7-3-31eb98fa5a8b@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:27 -07:00
Breno Leitao 82d9ff648c mm: huge_memory: refactor anon_enabled_store() with set_anon_enabled_mode() 
Consolidate the repeated spin_lock/set_bit/clear_bit pattern in
anon_enabled_store() into a new set_anon_enabled_mode() helper that loops
over an orders[] array, setting the bit for the selected mode and clearing
the others.

Introduce enum anon_enabled_mode and anon_enabled_mode_strings[] for the
per-order anon THP setting.

Use sysfs_match_string() with the anon_enabled_mode_strings[] table to
replace the if/else chain of sysfs_streq() calls.

The helper uses __test_and_set_bit()/__test_and_clear_bit() to track
whether the state actually changed, so start_stop_khugepaged() is only
called when needed.  When the mode is unchanged,
set_recommended_min_free_kbytes() is called directly to preserve the
watermark recalculation behavior of the original code.

Link: https://lkml.kernel.org/r/20260317-thp_logs-v7-2-31eb98fa5a8b@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2026-04-05 13:53:27 -07:00