Changes in mmap_prepare.rst

0fc8f6200d2313278fbf4539bbab74677c685531 - Merge drm/drm-fixes into drm-misc-fixes

Mon, 27 Apr 2026 10:26:49 +0200

Merge drm/drm-fixes into drm-misc-fixesGetting fixes and updates from v7.1-rc1.Signed-off-by: Thomas Zimmermann List of files: /linux/Documentation/filesystems/mmap_prepare.rst

334fbe734e687404f346eba7d5d96ed2b44d35ab - Merge tag 'mm-stable-2026-04-13-21-45' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Wed, 15 Apr 2026 21:59:16 +0200

Merge tag 'mm-stable-2026-04-13-21-45' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mmPull 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 ... List of files: /linux/Documentation/filesystems/mmap_prepare.rst

62c65fd740e979a3967db08971b93aefcec510d4 - mm: add mmap_action_map_kernel_pages[_full]()

Fri, 20 Mar 2026 23:39:46 +0100

mm: add mmap_action_map_kernel_pages[_full]()A user can invoke mmap_action_map_kernel_pages() to specify that themapping should map kernel pages starting from desc->start of a specifiednumber of pages specified in an array.In order to implement this, adjust mmap_action_prepare() to be able toreturn an error code, as it makes sense to assert that the specifiedparameters are valid as quickly as possible as well as updating the VMAflags to include VMA_MIXEDMAP_BIT as necessary.This provides an mmap_prepare equivalent of vm_insert_pages(). Weadditionally update the existing vm_insert_pages() code to userange_in_vma() and add a new range_in_vma_desc() helper function for themmap_prepare case, sharing the code between the two in range_is_subset().We add both mmap_action_map_kernel_pages() andmmap_action_map_kernel_pages_full() to allow for both partial and full VMAmappings.We update the documentation to reflect the new features.Finally, we update the VMA tests accordingly to reflect the changes.Link: https://lkml.kernel.org/r/926ac961690d856e67ec847bee2370ab3c6b9046.1774045440.git.ljs@kernel.orgSigned-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Suren Baghdasaryan Acked-by: Vlastimil Babka (SUSE) Cc: Alexander Shishkin Cc: Alexandre Torgue Cc: Al Viro Cc: Arnd Bergmann Cc: Bodo Stroesser Cc: Christian Brauner Cc: Clemens Ladisch Cc: David Hildenbrand Cc: David Howells Cc: Dexuan Cui Cc: Greg Kroah-Hartman Cc: Haiyang Zhang Cc: Jan Kara Cc: Jann Horn Cc: Jonathan Corbet Cc: K. Y. Srinivasan Cc: Liam Howlett Cc: Long Li Cc: Marc Dionne Cc: "Martin K. Petersen" Cc: Maxime Coquelin Cc: Michal Hocko Cc: Mike Rapoport Cc: Miquel Raynal Cc: Pedro Falcato Cc: Richard Weinberger Cc: Ryan Roberts Cc: Vignesh Raghavendra Cc: Wei Liu Signed-off-by: Andrew Morton List of files: /linux/Documentation/filesystems/mmap_prepare.rst

a1b7fb40cb71a33c68a609fcee0946425d698415 - mm: add mmap_action_simple_ioremap()

Fri, 20 Mar 2026 23:39:37 +0100

mm: add mmap_action_simple_ioremap()Currently drivers use vm_iomap_memory() as a simple helper function forI/O remapping memory over a range starting at a specified physical addressover a specified length.In order to utilise this from mmap_prepare, separate out the core logicinto __simple_ioremap_prep(), update vm_iomap_memory() to use it, and addsimple_ioremap_prepare() to do the same with a VMA descriptor object.We also add MMAP_SIMPLE_IO_REMAP and relevant fields to the structmmap_action type to permit this operation also.We use mmap_action_ioremap() to set up the actual I/O remap operation oncewe have checked and figured out the parameters, which makessimple_ioremap_prepare() easy to implement.We then add mmap_action_simple_ioremap() to allow drivers to make use ofthis mode.We update the mmap_prepare documentation to describe this mode. Finally,we update the VMA tests to reflect this change.Link: https://lkml.kernel.org/r/a08ef1c4542202684da63bb37f459d5dbbeddd91.1774045440.git.ljs@kernel.orgSigned-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Suren Baghdasaryan Acked-by: Vlastimil Babka (SUSE) Cc: Alexander Shishkin Cc: Alexandre Torgue Cc: Al Viro Cc: Arnd Bergmann Cc: Bodo Stroesser Cc: Christian Brauner Cc: Clemens Ladisch Cc: David Hildenbrand Cc: David Howells Cc: Dexuan Cui Cc: Greg Kroah-Hartman Cc: Haiyang Zhang Cc: Jan Kara Cc: Jann Horn Cc: Jonathan Corbet Cc: K. Y. Srinivasan Cc: Liam Howlett Cc: Long Li Cc: Marc Dionne Cc: "Martin K. Petersen" Cc: Maxime Coquelin Cc: Michal Hocko Cc: Mike Rapoport Cc: Miquel Raynal Cc: Pedro Falcato Cc: Richard Weinberger Cc: Ryan Roberts Cc: Vignesh Raghavendra Cc: Wei Liu Signed-off-by: Andrew Morton List of files: /linux/Documentation/filesystems/mmap_prepare.rst

c50ca15dd4962bdf834945c2fa29b904042f366a - mm: add vm_ops->mapped hook

Fri, 20 Mar 2026 23:39:34 +0100

mm: add vm_ops->mapped hookPreviously, when a driver needed to do something like establish areference count, it could do so in the mmap hook in the knowledge that themapping would succeed.With the introduction of f_op->mmap_prepare this is no longer the case, asit is invoked prior to actually establishing the mapping.mmap_prepare is not appropriate for this kind of thing as it is calledbefore any merge might take place, and after which an error might occurmeaning resources could be leaked.To take this into account, introduce a new vm_ops->mapped callback whichis invoked when the VMA is first mapped (though notably - not when it ismerged - which is correct and mirrors existing mmap/open/close behaviour).We do better that vm_ops->open() here, as this callback can return anerror, at which point the VMA will be unmapped.Note that vm_ops->mapped() is invoked after any mmap action is complete(such as I/O remapping).We intentionally do not expose the VMA at this point, exposing only thefields that could be used, and an output parameter in case the operationneeds to update the vma->vm_private_data field.In order to deal with stacked filesystems which invoke inner filesystem'smmap() invocations, add __compat_vma_mapped() and invoke it on vfs_mmap()(via compat_vma_mmap()) to ensure that the mapped callback is handled whenan mmap() caller invokes a nested filesystem's mmap_prepare() callback.Update the mmap_prepare documentation to describe the mapped hook and makeit clear what its intended use is.The vm_ops->mapped() call is handled by the mmap complete logic to ensurethe same code paths are handled by both the compatibility and VMA layers.Additionally, update VMA userland test headers to reflect the change.Link: https://lkml.kernel.org/r/4c5e98297eb0aae9565c564e1c296a112702f144.1774045440.git.ljs@kernel.orgSigned-off-by: Lorenzo Stoakes (Oracle) Acked-by: Vlastimil Babka (SUSE) Cc: Alexander Shishkin Cc: Alexandre Torgue Cc: Al Viro Cc: Arnd Bergmann Cc: Bodo Stroesser Cc: Christian Brauner Cc: Clemens Ladisch Cc: David Hildenbrand Cc: David Howells Cc: Dexuan Cui Cc: Greg Kroah-Hartman Cc: Haiyang Zhang Cc: Jan Kara Cc: Jann Horn Cc: Jonathan Corbet Cc: K. Y. Srinivasan Cc: Liam Howlett Cc: Long Li Cc: Marc Dionne Cc: "Martin K. Petersen" Cc: Maxime Coquelin Cc: Michal Hocko Cc: Mike Rapoport Cc: Miquel Raynal Cc: Pedro Falcato Cc: Richard Weinberger Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Vignesh Raghavendra Cc: Wei Liu Signed-off-by: Andrew Morton List of files: /linux/Documentation/filesystems/mmap_prepare.rst

fdd247841380d86c9e38027cb519b6fc45930a83 - mm: add documentation for the mmap_prepare file operation callback

Fri, 20 Mar 2026 23:39:28 +0100

mm: add documentation for the mmap_prepare file operation callbackThis documentation makes it easier for a driver/file system implementer tocorrectly use this callback.It covers the fundamentals, whilst intentionally leaving the less lovelypossible actions one might take undocumented (for instance - thesuccess_hook, error_hook fields in mmap_action).The document also covers the new VMA flags implementation which is theonly one which will work correctly with mmap_prepare.Link: https://lkml.kernel.org/r/3aebf918c213fa2aecf00a31a444119b5bdd7801.1774045440.git.ljs@kernel.orgSigned-off-by: Lorenzo Stoakes (Oracle) Acked-by: Vlastimil Babka (SUSE) Cc: Alexander Shishkin Cc: Alexandre Torgue Cc: Al Viro Cc: Arnd Bergmann Cc: Bodo Stroesser Cc: Christian Brauner Cc: Clemens Ladisch Cc: David Hildenbrand Cc: David Howells Cc: Dexuan Cui Cc: Greg Kroah-Hartman Cc: Haiyang Zhang Cc: Jan Kara Cc: Jann Horn Cc: Jonathan Corbet Cc: K. Y. Srinivasan Cc: Liam Howlett Cc: Long Li Cc: Marc Dionne Cc: "Martin K. Petersen" Cc: Maxime Coquelin Cc: Michal Hocko Cc: Mike Rapoport Cc: Miquel Raynal Cc: Pedro Falcato Cc: Richard Weinberger Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Vignesh Raghavendra Cc: Wei Liu Signed-off-by: Andrew Morton List of files: /linux/Documentation/filesystems/mmap_prepare.rst