kernel/git/stable/linux.git/mm/migrate.c, branch master

mm/migrate: calculate large folio page index using PFN

2026-08-25T01:42:53+00:00

Rather than having to figure out the page index to use using linear_page_index(), calculate it using PFN. This is a more natural fit as the linear page index is immaterial to determining the folio page index. Derive the page index from the offset between migration entry PFN and folio PFN - pvmw.pfn (set via DEFINE_FOLIO_VMA_WALK() which uses folio_pfn() to obtain it). Additionally remove a not so useful comment and clean the code layout up. No functional change intended. Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-13-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Suggested-by: David Hildenbrand (Arm) Acked-by: David Hildenbrand (Arm) Cc: Adrian Hunter Cc: Alexander Deucher Cc: Alexander Gordeev Cc: Alexander Shishkin Cc: Alistair Popple Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Boris Brezillon Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christan König Cc: Christian Borntraeger Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dev Jain Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price (Meta) Cc: Harry Yoo Cc: Heiko Carstens Cc: Huang Ray Cc: "Huang, Ying" Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: John Hubbard Cc: Joshua Hahn Cc: Kairui Song Cc: Kees Cook Cc: Kemeng Shi Cc: Lance Yang Cc: Liam R. Howlett Cc: Liviu Dudau Cc: Maarten Lankhorst Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Matthew Auld Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Namhyung kim Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Rodrigo Vivi Cc: Ryan Roberts Cc: Steven Price Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Hellström Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

mm/huge_memory: update remove_migration_pmd() to accept a folio

2026-08-25T01:42:52+00:00

This function does not need to accept a page and requiring it to is unnecessary and misleading. make_[writable, readable]_device_private_entry() must be passed a PMD-aligned PFN as they immediately used to obtain a softleaf PMD entry and the same argument applies to folio_add_[anon, file]_rmap_pmd(). While we are here, update a VM_BUG_ON() to a VM_WARN_ON_ONCE(). No functional change intended. Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-12-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Cc: Adrian Hunter Cc: Alexander Deucher Cc: Alexander Gordeev Cc: Alexander Shishkin Cc: Alistair Popple Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Boris Brezillon Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christan König Cc: Christian Borntraeger Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dev Jain Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price (Meta) Cc: Harry Yoo Cc: Heiko Carstens Cc: Huang Ray Cc: "Huang, Ying" Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: John Hubbard Cc: Joshua Hahn Cc: Kairui Song Cc: Kees Cook Cc: Kemeng Shi Cc: Lance Yang Cc: Liam R. Howlett Cc: Liviu Dudau Cc: Maarten Lankhorst Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Matthew Auld Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Namhyung kim Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Rodrigo Vivi Cc: Ryan Roberts Cc: Steven Price Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Hellström Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()

2026-08-07T01:57:25+00:00

migrate_pages_batch() unmaps each folio before moving it, and every unmap runs the mmu_notifier invalidate callbacks. On KVM hosts try_to_migrate() ends up in kvm_mmu_notifier_invalidate_range_start() -> tdp_mmu_zap_leafs(), which is expensive, so unmapping a large batch keeps the CPU busy for a long time. The loop already calls cond_resched(), but on PREEMPTION kernels that is a no-op, and involuntary preemption is not a Tasks-RCU quiescent state. A long batch therefore never reports a quiescent state, and the migrating task (e.g. kcompactd) becomes a Tasks-RCU holdout, stalling the Tasks-RCU grace period for minutes, which is common at Meta fleet: INFO: rcu_tasks detected stalls on tasks: 0000000055349ecc: .. nvcsw: 1157401/1157401 holdout: 1 idle_cpu: -1/56 task:kcompactd0 state:R running task Call Trace: tdp_mmu_zap_leafs tdp_mmu_next_root gfn_to_pfn_cache_invalidate_start kvm_mmu_notifier_invalidate_range_start __mmu_notifier_invalidate_range_start try_to_migrate_one try_to_migrate migrate_pages_batch migrate_pages compact_zone compact_node kcompactd kthread Use cond_resched_tasks_rcu_qs() so a quiescent state is reported even when cond_resched() does nothing. This has also been discussed at [1] Link: https://lore.kernel.org/20260727-kcompact-v1-1-bdfefddd6874@debian.org Link: https://lore.kernel.org/all/amdWVTs0WKOxguxP@gmail.com/ [1] Signed-off-by: Breno Leitao Acked-by: Zi Yan Reviewed-by: Gregory Price Reviewed-by: Paul E. McKenney Acked-by: David Hildenbrand (Arm) Cc: Alistair Popple Cc: Byungchul Park Cc: "Huang, Ying" Cc: Joshua Hahn Cc: Matthew Brost Cc: Rakie Kim Cc: Signed-off-by: Andrew Morton

mm: preserve RWP marker across PTE rewrites

2026-08-05T02:18:37+00:00

The uffd PTE bit must survive any kernel path that rewrites a PTE on a VM_UFFD_RWP VMA, otherwise the marker that carries PAGE_NONE semantics is silently dropped and the next access leaks past RWP tracking. Wire the preservation through every path that rewrites a VM_UFFD_RWP PTE. Swap and device-exclusive: do_swap_page(), restore_exclusive_pte(), and unuse_pte() (swapoff()) re-apply PAGE_NONE when the swap PTE carries the uffd bit and the VMA has VM_UFFD_RWP. Migration: remove_migration_pte() and remove_migration_pmd() do the same after the migration entry is replaced with a real PTE/PMD. Fork: __copy_present_ptes(), copy_present_page(), copy_nonpresent_pte(), copy_huge_pmd(), copy_huge_non_present_pmd(), and copy_hugetlb_page_range() keep the uffd bit on the child when the destination VMA has VM_UFFD_RWP, matching the existing VM_UFFD_WP handling. Add VM_UFFD_RWP to VM_COPY_ON_FORK so the flag itself propagates. mprotect(): change_pte_range() and change_huge_pmd() restore PAGE_NONE after pte_modify()/pmd_modify() have recomputed the base protection from a (possibly user-changed) vm_page_prot. pte_modify() preserves _PAGE_UFFD, so the bit stays; we just have to force PAGE_NONE back on top. Link: https://lore.kernel.org/20260708111417.173443-8-kirill@shutemov.name Signed-off-by: Kiryl Shutsemau Assisted-by: Claude:claude-opus-4-6 Acked-by: Mike Rapoport (Microsoft) Cc: Andrea Arcangeli Cc: David Hildenbrand Cc: James Houghton Cc: Jonathan Corbet Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Paolo Bonzini Cc: Peter Xu Cc: Sean Christopherson Cc: SeongJae Park Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton

mm: rename uffd-wp PTE accessors to uffd

2026-08-05T02:18:36+00:00

Userfaultfd RWP will reuse the uffd-wp PTE bit to mark access-tracking PTEs, alongside the write-protected ones it already marks. The bit's meaning now depends on the VMA flag (WP or RWP), not on its name. Rename the kernel-internal names that describe the bit: - pte/pmd/huge_pte accessors (and swap variants) - pgtable_supports_uffd() capability query - SCAN_PTE_UFFD khugepaged enum The ftrace string emitted by mm_khugepaged_scan_pmd for this enum is kept as "pte_uffd_wp" so existing trace-based tooling keeps matching. Pure mechanical rename -- no behavior change. Link: https://lore.kernel.org/20260708111417.173443-4-kirill@shutemov.name Signed-off-by: Kiryl Shutsemau Assisted-by: Claude:claude-opus-4-6 Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: SeongJae Park Cc: Andrea Arcangeli Cc: David Hildenbrand Cc: James Houghton Cc: Jonathan Corbet Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Paolo Bonzini Cc: Peter Xu Cc: Sean Christopherson Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton

Merge branch 'mm-hotfixes-stable' into mm-stable in order to pick up

2026-08-05T02:15:12+00:00

vmscan.c changes which are required by "memcg: bail out proactive reclaim when memcg is dying".

mm/migrate: use huge_ptep_get() in remove_migration_pte()

2026-07-31T02:40:45+00:00

remove_migration_pte() converts migration entries back to present PTEs after folio migration completes. For hugetlb folios, page_vma_mapped_walk() returns the pte pointer to the hugetlb folio in pvmw.pte, but the code reads it with ptep_get(). On arches which provide their own huge_ptep_get() to dereference a huge pte pointer, accessing via ptep_get() would cause pte_pfn(), pte_present() etc to misbehave. It is not clear whether this has a trivially visible effect to userspace. Use huge_ptep_get() to dereference a huge pte pointer. Link: https://lore.kernel.org/20260703114202.365553-5-dev.jain@arm.com Fixes: 290408d4a250 ("hugetlb: hugepage migration core") Signed-off-by: Dev Jain Acked-by: Muchun Song Acked-by: David Hildenbrand (Arm) Cc: Alistair Popple Cc: Andi Kleen Cc: Anshuman Khandual Cc: Byungchul Park Cc: Catalin Marinas Cc: Dave Hansen Cc: Gregory Price Cc: Harry Yoo Cc: "Huang, Ying" Cc: Jann Horn Cc: Josh Poimboeuf Cc: Joshua Hahn Cc: Jun'ichi "Nick" Nomura Cc: Kiryl Shutsemau Cc: Lance Yang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Matthew Brost Cc: Mel Gorman Cc: Naoya Horiguchi Cc: Oscar Salvador Cc: Pedro Falcato Cc: Rakie Kim Cc: Ralph Campbell Cc: Rik van Riel Cc: Ryan Roberts Cc: Vlastimil Babka Cc: Will Deacon Cc: Zi Yan Cc: Signed-off-by: Andrew Morton

mm: split out internal page_alloc.h

2026-07-31T02:40:41+00:00

internal.h is a bit bloated, seems like time for a page_alloc.h. Where it wasn't obvious, the heuristic for deciding what goes into this new header was "does it support/correspond to a definition in mm/page_alloc.c?" Only need to include it from ~20 .c files out of ~150 so this does seem like a genuine reduction in scopes, which is nice. And there's no circular internal.h<->page_alloc.h dependency, so it seems worthwhile to split this up before that inevitably emerges! Link: https://lore.kernel.org/20260703-alloc-trylock-v5-4-c87b714e19d3@google.com Signed-off-by: Brendan Jackman Suggested-by: "David Hildenbrand (Arm)" Link: https://lore.kernel.org/all/41e92bab-6882-401a-8de9-154adbdcfb36@kernel.org/ Reviewed-by: Vlastimil Babka (SUSE) Acked-by: Zi Yan Signed-off-by: Andrew Morton

mm: rename ARCH_ENABLE_THP_MIGRATION to ARCH_HAS_PMD_SOFTLEAVES

2026-07-31T02:40:25+00:00

CONFIG_ARCH_ENABLE_THP_MIGRATION gates PMD-level migration entries. PMD-level device-private entries use the same migration mechanism and therefore require the same architecture support. Upcoming PMD-level swap entries can use the same PMD softleaf helpers without depending on page migration, so rename the architecture gate to CONFIG_ARCH_HAS_PMD_SOFTLEAVES. This describes the PMD entry capability rather than one current user of it. This is a pure rename: the set of selecting architectures (x86, arm64, s390, riscv, loongarch, and powerpc on PPC_BOOK3S_64) and the gating semantics are unchanged. No functional change intended. Link: https://lore.kernel.org/20260706114320.1643046-7-usama.arif@linux.dev Signed-off-by: Usama Arif Reviewed-by: Zi Yan Acked-by: David Hildenbrand (Arm) Cc: Alexandre Ghiti Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Chris Li Cc: Dev Jain Cc: "Huang, Ying" Cc: Johannes Weiner Cc: Kairui Song Cc: Kemeng Shi Cc: Kiryl Shutsemau Cc: Lance Yang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Nhat Pham Cc: Nico Pache Cc: Rik van Riel Cc: Ryan Roberts Cc: Shakeel Butt Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/migrate: use migrate_info field instead of private

2026-07-29T04:11:53+00:00

Add an unsigned long migrate_info member to the struct folio union and use it to store migration state (anon_vma pointer and FOLIO_WAS_* markers) instead of using folio->private. While at it, switch to bitwise OR. No functional change. [rdunlap@infradead.org: add missing kernel-doc for @migrate_info] Link: https://lore.kernel.org/20260717022146.1290242-1-rdunlap@infradead.org Link: https://lore.kernel.org/20260701-migrate-cleanups-prep-v2-3-d9e8f17130b1@amd.com Signed-off-by: Shivank Garg Suggested-by: David Hildenbrand (Arm) Reviewed-by: Jonathan Cameron Acked-by: David Hildenbrand (Arm) Reviewed-by: Huang Ying Acked-by: Zi Yan Reviewed-by: SJ Park Signed-off-by: Randy Dunlap Cc: Alistair Popple Cc: Byungchul Park Cc: Dev Jain Cc: Gregory Price Cc: Joshua Hahn Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Matthew Brost Cc: Michal Hocko Cc: Mike Rapoport Cc: Rakie Kim Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton