kernel/linux.git/mm/huge_memory.c, branch v7.2-rc1

Merge tag 'mm-stable-2026-06-23-08-55' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-06-23T19:03:44+00:00

Pull more MM updates from Andrew Morton: - "khugepaged: add mTHP collapse support" (Nico Pache) Provide khugepaged with the capability to collapse anonymous memory regions to mTHPs - "Remove CONFIG_READ_ONLY_THP_FOR_FS and enable file THP for writable files" (Zi Yan) Remove the READ_ONLY_THP_FOR_FS check in file_thp_enabled(), so that khugepaged and MADV_COLLAPSE can run on filesystems with PMD THP pagecache support even without READ_ONLY_THP_FOR_FS enabled - "make MM selftests more CI friendly" (Mike Rapoport) General fixes and cleanups to the MM selftests. Also move more MM selftests under the kselftest framework, making them more amenable to ongoing CI testing - "selftests/mm: fix failures and robustness improvements" and "selftests/mm: assorted fixes for hmm-tests" (Sayali Patil) Fix several issues in MM selftests which were revealed by powerpc 64k pagesize * tag 'mm-stable-2026-06-23-08-55' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (118 commits) Revert "mm: limit filemap_fault readahead to VMA boundaries" mm/vmscan: pass NULL to trace vmscan node reclaim mm: use mapping_mapped to simplify the code selftests/mm: fix exclusive_cow test fork() handling selftests/mm: remove hardcoded THP sizing assumptions in hmm tests selftests/mm: allow PUD-level entries in compound testcase of hmm tests mm/gup_test: reject wrapped user ranges mm/page_frag: reject invalid CPUs in page_frag_test mm/damon/core: always put unsuccessfully committed target pids mm: page_isolation: avoid unsafe folio reads while scanning compound pages mm/shrinker: do not hold RCU lock in shrinker_debugfs_count_show() selftests: mm: fix and speedup "droppable" test mm: merge writeout into pageout MAINTAINERS: add Hao Ge as reviewer for codetag and alloc_tag selftests/mm: clarify alternate unmapping in compaction_test selftests/mm: move hwpoison setup into run_test() and silence modprobe output for memory-failure category selftests/mm: skip uffd-stress test when nr_pages_per_cpu is zero selftests/mm: skip uffd-wp-mremap if UFFD write-protect is unsupported selftests/mm: ensure destination is hugetlb-backed in hugetlb-mremap selftest/mm: register existing mapping with userfaultfd in hugetlb-mremap ...

mm/khugepaged: enable clean pagecache folio collapse for writable files

2026-06-21T18:37:17+00:00

collapse_file() is capable of collapsing pagecache folios from writable files to PMD folios. Now enable clean pagecache folio collapse in addition to read-only pagecache folio collapse by removing the inode_is_open_for_write() from file_thp_enabled() and only performing filemap_flush() if the file is read-only. This means userspace needs to explicitly flush the content of pagecache folios before khugepaged can collapse the folios, or use madvise(MADV_COLLAPSE), which does the flush in the retry. The reason is that blindly enabling dirty pagecache folio from writable files collapse makes khugepaged flush these folios all the time. It is undesirable to cause system level pagecache flushes. To properly support dirty pagecache folio collapse, filemap_flush() needs to be avoided. Potentially, merging associated buffer instead of dropping it with filemap_release_folio() might be needed. NOTE: this breaks khugepaged selftests for writable file pagecache collapse, which is set to fail all the time. The next commit fixes it. Link: https://lore.kernel.org/20260517135416.1434539-14-ziy@nvidia.com Signed-off-by: Zi Yan Reviewed-by: Lance Yang Cc: Al Viro Cc: Baolin Wang Cc: Barry Song Cc: Chris Mason Cc: Christian Brauner Cc: David Hildenbrand (Arm) Cc: David Sterba Cc: Dev Jain Cc: Jan Kara Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Ryan Roberts Cc: Shuah Khan Cc: Song Liu Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/huge_memory: remove folio split check for READ_ONLY_THP_FOR_FS

2026-06-21T18:37:15+00:00

Without READ_ONLY_THP_FOR_FS, large file-backed folios cannot be created by a FS without large folio support. The check is no longer needed. Link: https://lore.kernel.org/20260517135416.1434539-9-ziy@nvidia.com Signed-off-by: Zi Yan Reviewed-by: Lance Yang Reviewed-by: Lorenzo Stoakes (Oracle) Reviewed-by: Baolin Wang Acked-by: David Hildenbrand (Arm) Cc: Al Viro Cc: Barry Song Cc: Chris Mason Cc: Christian Brauner Cc: David Sterba Cc: Dev Jain Cc: Jan Kara Cc: Liam Howlett Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Ryan Roberts Cc: Shuah Khan Cc: Song Liu Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm: fs: remove filemap_nr_thps*() functions and their users

2026-06-21T18:37:15+00:00

They are used by READ_ONLY_THP_FOR_FS to handle writes to FSes without large folio support, so that read-only THPs created in these FSes are not seen by the FSes when the underlying fd becomes writable. Now read-only PMD THPs only appear in a FS with large folio support and the supported orders include PMD_ORDER. READ_ONLY_THP_FOR_FS was using mapping->nr_thps, inode->i_writecount, and smp_mb() to prevent writes to a read-only THP and collapsing writable folios into a THP. In collapse_file(), mapping->nr_thps is increased, then smp_mb(), and if inode->i_writecount > 0, collapse is stopped, while do_dentry_open() first increases inode->i_writecount, then a full memory fence, and if mapping->nr_thps > 0, all read-only THPs are truncated. Now this mechanism can be removed along with READ_ONLY_THP_FOR_FS code, since a dirty folio check has been added after try_to_unmap() in collapse_file() to prevent dirty folios from being collapsed as clean. Link: https://lore.kernel.org/20260517135416.1434539-7-ziy@nvidia.com Signed-off-by: Zi Yan Reviewed-by: Matthew Wilcox (Oracle) Acked-by: David Hildenbrand (Arm) Reviewed-by: Baolin Wang Reviewed-by: Lance Yang Cc: Al Viro Cc: Barry Song Cc: Chris Mason Cc: Christian Brauner Cc: David Sterba Cc: Dev Jain Cc: Jan Kara Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Ryan Roberts Cc: Shuah Khan Cc: Song Liu Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled()

2026-06-21T18:37:14+00:00

Replace it with a check on the max folio order of the file's address space mapping, making sure PMD folio is supported. Keep the inode open-for-write check, since even if collapse_file() now makes sure all to-be-collapsed folios are clean and the created PMD file THP can be handled by FSes properly, the filemap_flush() could perform undesirable write back. Link: https://lore.kernel.org/20260517135416.1434539-4-ziy@nvidia.com Signed-off-by: Zi Yan Acked-by: David Hildenbrand (Arm) Reviewed-by: Lance Yang Reviewed-by: Nico Pache Cc: Al Viro Cc: Baolin Wang Cc: Barry Song Cc: Chris Mason Cc: Christian Brauner Cc: David Sterba Cc: Dev Jain Cc: Jan Kara Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Ryan Roberts Cc: Shuah Khan Cc: Song Liu Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/khugepaged: add per-order mTHP collapse failure statistics

2026-06-21T18:31:31+00:00

Add three new mTHP statistics to track collapse failures for different orders when encountering swap PTEs, excessive none PTEs, and shared PTEs: - collapse_exceed_swap_pte: Increment when mTHP collapse fails due to encountering a swap PTE. - collapse_exceed_none_pte: Counts when mTHP collapse fails due to exceeding the none PTE threshold for the given order - collapse_exceed_shared_pte: Counts when mTHP collapse fails due to encountering a shared PTE. These statistics complement the existing THP_SCAN_EXCEED_* events by providing per-order granularity for mTHP collapse attempts. The stats are exposed via sysfs under `/sys/kernel/mm/transparent_hugepage/hugepages-*/stats/` for each supported hugepage size. As we currently do not support collapsing mTHPs that contain a swap or shared entry, those statistics keep track of how often we are encountering failed mTHP collapses due to these restrictions. We will add support for mTHP collapse for anonymous pages next; lets also track when this happens at the PMD level within the per-mTHP stats. Link: https://lore.kernel.org/20260605161422.213817-9-npache@redhat.com Signed-off-by: Nico Pache Reviewed-by: Lorenzo Stoakes Acked-by: David Hildenbrand (Arm) Reviewed-by: Lance Yang Cc: Alistair Popple Cc: Andrea Arcangeli Cc: Anshuman Khandual Cc: Bagas Sanjaya Cc: Baolin Wang Cc: Barry Song Cc: Brendan Jackman Cc: Byungchul Park Cc: Catalin Marinas Cc: David Rientjes Cc: Dev Jain Cc: Gregory Price Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Kefeng Wang Cc: Liam R. Howlett Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Nanyong Sun Cc: Pedro Falcato Cc: Peter Xu Cc: Rafael Aquini Cc: Rakie Kim Cc: Randy Dunlap Cc: Ryan Roberts Cc: Shivank Garg Cc: Steven Rostedt Cc: Suren Baghdasaryan Cc: Takashi Iwai (SUSE) Cc: Thomas Hellström Cc: Usama Arif Cc: Usama Arif Cc: Vishal Moola (Oracle) Cc: Vlastimil Babka Cc: Wei Yang Cc: Will Deacon Cc: Yang Shi Cc: Zach O'Keefe Cc: Zi Yan Signed-off-by: Andrew Morton

mm/khugepaged: generalize alloc_charge_folio()

2026-06-21T18:31:29+00:00

Pass order to alloc_charge_folio() and update mTHP statistics. Link: https://lore.kernel.org/20260605161422.213817-3-npache@redhat.com Signed-off-by: Dev Jain Co-developed-by: Nico Pache Signed-off-by: Nico Pache Reviewed-by: Wei Yang Reviewed-by: Lance Yang Reviewed-by: Baolin Wang Reviewed-by: Lorenzo Stoakes Reviewed-by: Zi Yan Acked-by: Usama Arif Acked-by: David Hildenbrand (Arm) Cc: Alistair Popple Cc: Andrea Arcangeli Cc: Anshuman Khandual Cc: Bagas Sanjaya Cc: Barry Song Cc: Brendan Jackman Cc: Byungchul Park Cc: Catalin Marinas Cc: David Rientjes Cc: Gregory Price Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Kefeng Wang Cc: Liam R. Howlett Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Nanyong Sun Cc: Pedro Falcato Cc: Peter Xu Cc: Rafael Aquini Cc: Rakie Kim Cc: Randy Dunlap Cc: Ryan Roberts Cc: Shivank Garg Cc: Steven Rostedt Cc: Suren Baghdasaryan Cc: Takashi Iwai (SUSE) Cc: Thomas Hellström Cc: Usama Arif Cc: Vishal Moola (Oracle) Cc: Vlastimil Babka Cc: Will Deacon Cc: Yang Shi Cc: Zach O'Keefe Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2026-06-18-09-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-06-19T17:14:34+00:00

Pull MM updates from Andrew Morton: - "selftests/mm: clean up build output and verbosity" (Li Wang) Remove some noise from the MM selftests build - "mm: Free contiguous order-0 pages efficiently" (Ryan Roberts) Speed up the freeing of a batch of 0-order pages by first scanning them for coalescing opportunities. This is applicable to vfree() and to the releasing of frozen pages - "mm/damon: introduce DAMOS failed region quota charge ratio" (SeongJae Park) Address a DAMOS usability issue: The DAMOS quota often exhausts prematurely because it charges for all memory attempted, causing slow and inconsistent performance when actions fail on unreclaimable memory. To fix this, a new feature lets users set a smaller, flexible quota charge ratio (via a numerator and denominator) for failed regions. Since failed actions cause less overhead, reducing their quota cost ensures more predictable and efficient DAMOS processing - "selftests/cgroup: improve zswap tests robustness and support large page sizes" (Li Wang) Fix various spurious failures and improves the overall robustness of the cgroup zswap selftests - "fix MAP_DROPPABLE not supported errno" (Anthony Yznaga) Fix an issue in the mlock selftests on arm32 - "mm: huge_memory: clean up defrag sysfs with shared" (Breno Leitao) Some maintenance work in the huge_memory code - "treewide: fixup gfp_t printks" (Brendan Jackman) Use the special vprintf() gfp_t conversion in various places - "mm: Fix vmemmap optimization accounting and initialization" (Muchun Song) Fix several bugs in the vmemmap optimization, mainly around incorrect page accounting and memmap initialization in the DAX and memory hotplug paths. It also fixes pageblock migratetype initialization and struct page initialization for ZONE_DEVICE compound pages - "mm/damon: repost non-hotfix reviewed patches in damon/next tree" A sprinkle of unrelated minor bugfixes for DAMON - "mm: remove page_mapped()" (David Hildenbrand) Remove this function from the tree, replacing it with folio_mapped() - "mm/damon: let DAMON be paused and resumed" (SeongJae Park) Allow DAMON to be paused and resumed without losing its current state - "kasan: hw_tags: Disable tagging for stack and page-tables" (Muhammad Usama Anjum) Simplify and speed up kasan by removing its ineffective tagging of stacks and page tables - "mm/damon/reclaim,lru_sort: monitor all system rams by default" (SeongJae Park) Simplify deployment on diverse hardware like NUMA systems by updating DAMON_RECLAIM and DAMON_LRU_SORT to automatically monitor the physical address range covering all System RAM areas by default, replacing the overly restrictive behavior that only targeted the single largest memory block to save on negligible overhead - "mm/damon/sysfs: document filters/ directory as deprecated" (SeongJae Park) Update some DAMON docs - "mm: use spinlock guards for zone lock" (Dmitry Ilvokhin) Switch zone->lock handling over to using the guard() mechanisms - "mm/filemap: tighten mmap_miss hit accounting" (fujunjie) Fix a flaw where the mmap_miss counter over-credited page cache hits during fault-arounds and page-fault retries. This results in significant reduction of redundant synchronous mmap readahead I/O, drastically cutting down execution time and gigabytes read for sparse random or strided memory access workloads - "selftests/cgroup: Fix false positive failures in test_percpu_basic" (Li Wang) Fix a couple of false-positives in the cgroup kmem selftests - "mm/damon/reclaim: support monitoring intervals auto-tuning" (SeongJae Park) Add a new parameter to DAMON permitting DAMON_RECLAIM to automatically tune DAMON's sampling and aggregation intervals - "mm/damon/stat: add kdamond_pid parameter" (SeongJae Park) Change DAMON_STAT to provide the pid of its kdamond - "mm/kmemleak: dedupe verbose scan output" (Breno Leitao) Remove large amounts of duplicated backtraces from the verbose-mode kmemleak output - "mm: remove CONFIG_HAVE_BOOTMEM_INFO_NODE (Part 1)" (David Hildenbrand) Reduce our use of CONFIG_HAVE_BOOTMEM_INFO_NODE, with a view to removing it entirely in a later series - "mm/damon: validate min_region_size to be power of 2" (Liew Rui Yan) Prevent users from passing a non-power-of-2 value of `addr_unit', as this later results in undesirable behavior - "mm: document read_pages and simplify usage" (Frederick Mayle) - "tools/mm/page-types: Fix misc bugs" (Ye Liu) Fix three issues in tools/mm/page-types.c - "mm: misc cleanups from __GFP_UNMAPPED series" (Brendan Jackman) Implement several cleanups in the page allocator and related code - "mm, swap: swap table phase IV: unify allocation" (Kairui Song) Unify the allocation and charging of anon and shmem swap in folios, provides better synchronization, consolidates the metadata management, hence dropping the static array and map, and improves performance - "mm/damon: introduce data attributes monitoring" (SeongJae Park( Extend DAMON to monitor general data attributes other than accesses - "mm/vmalloc: free unused pages on vrealloc() shrink" (Shivam Kalra) Implement the TODO in vrealloc() to unmap and free unused pages when shrinking across a page boundary - "mm/damon: documentation and comment fixes" (niecheng) - "remove mmap_action success, error hooks" (Lorenzo Stoakes) Eliminate custom hooks from mmap_action by removing the problematic success_hook which allowed drivers to improperly access uninitialized VMAs. It replaces the error_hook with a simple error-code field and updates the memory char driver accordingly - "mm/damon: minor improvements for code readability and tests" (SeongJae Park) - "mm/damon: fix macro arguments and clarify quota goals doc" (Maksym Shcherba) - "userfaultfd: merge fs/userfaultfd.c into mm/userfaultfd.c" (Mike Rapoport) - "mm/mglru: improve reclaim loop and dirty folio" (Kairui Song and others) Clean up and slightly improves MGLRU's reclaim loop and dirty writeback handling. Large performance improvements are measured - "use vma locks for proc/pid/{smaps|numa_maps} reads" (Suren Baghdasaryan) Use per-vma locks when reading /proc/pid/smaps and numa_maps similar to reduce contention on central mmap_lock - "refactors thpsize_shmem_enabled_store() and thpsize_shmem_enabled_show()" (Ran Xiaokai) Some cleanup work in the THP code - "selftests/memfd: fix compilation warnings" (Konstantin Khorenko) Fix a few build glitches in the memfd selftest code. - "memcg: shrink obj_stock_pcp and cache multiple objcgs" (Shakeel Butt) Resolve a 68% performance regression caused by NUMA-node cache thrashing around struct obj_stock_pcp by shrinking its existing fields and expanding it into a multi-slot array that caches up to five obj_cgroup pointers per CPU, allowing per-node variants of the same memcg to coexist within a single 64-byte cache line. - "zram: writeback fixes" (Sergey Senozhatsky) address a couple of unrelated zram writeback issues - "mm: switch THP shrinker to list_lru" (Johannes Weiner) Resolve NUMA-awareness issues and streamlines callsite interaction by refactoring and extending the list_lru API to completely replace the complex, open-coded deferred split queue for Transparent Huge Pages - "mm: improve large folio readahead for exec memory" (Usama Arif) Improve large-folio readahead on systems like 64K-page arm64 by preventing the mmap_miss check from permanently disabling target-oriented VM_EXEC readahead, and by generalizing the force_thp_readahead gate to support mappings with any usefully large maximum folio order under the cache cap. - "userfaultfd/pagemap: pre-existing fixes" (Kiryl Shutsemau) Fix a bunch of minor issues in the userfaultfd/pagemap, all of which were flagged by Sashiko review of proposed new material - "mm/sparse-vmemmap: Provide generic vmemmap_set_pmd() and vmemmap_check_pmd()" (Muchun Song) Provide generic versions of these two functions so the four arch-specific implementations can be removed. - "mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device" (Youngjun Park) Address a uswsusp-vs-swapoff race and reduces the swap device reference taking/releasing frequency. - "mm/hmm: A fix and a selftest" (Dev Jain) * tag 'mm-stable-2026-06-18-09-26' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits) selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries fs/proc/task_mmu: do not warn on seeing non-migration pmd entry lib/test_hmm: check alloc_page_vma() return value and handle OOM mm/compaction: cap compact_gap() at COMPACT_CLUSTER_MAX mm/swap: remove redundant swap device reference in alloc/free mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device mm/filemap: use folio_next_index() for start vmalloc: fix NULL pointer dereference in is_vm_area_hugepages() sparc/mm: drop vmemmap_check_pmd helper and use generic code loongarch/mm: drop vmemmap_check_pmd helper and use generic code riscv/mm: drop vmemmap_pmd helpers and use generic code arm64/mm: drop vmemmap_pmd helpers and use generic code mm/sparse-vmemmap: provide generic vmemmap_set_pmd() and vmemmap_check_pmd() rust: page: mark Page::nid as inline userfaultfd: build __VMA_UFFD_FLAGS from config-gated masks userfaultfd: gate must_wait writability check on pte_present() mm/huge_memory: preserve pmd_swp_uffd_wp on device-private PMD downgrade fs/proc/task_mmu: fix hugetlb self-deadlock in pagemap_scan_pte_hole() fs/proc/task_mmu: use huge_page_size() in pagemap_scan_hugetlb_entry() fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race ...

Merge tag 'vfs-7.2-rc1.writeback' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-06-14T22:00:45+00:00

Pull vfs writeback updates from Christian Brauner: - Fix a race between cgroup_writeback_umount() and inode_switch_wbs() When a container exits, a race between cgroup_writeback_umount() and inode_switch_wbs()/cleanup_offline_cgwb() can trigger "VFS: Busy inodes after unmount" followed by a use-after-free on percpu counters. There is a window between inode_prepare_wbs_switch() returning true (having passed the SB_ACTIVE check and grabbed the inode) and the subsequent wb_queue_isw() call: if cgroup_writeback_umount() observes the global isw_nr_in_flight counter as non-zero but flush_workqueue() finds nothing queued yet, it returns early - leaving a held inode reference that blocks evict_inodes() and a later iput() that hits freed percpu counters. The race is closed by covering the window from inode_prepare_wbs_switch() through wb_queue_isw() with an RCU read-side critical section and synchronizing in the umount path. On top of that the now-dead rcu_barrier() left over from the queue_rcu_work() era is removed, and the global synchronize_rcu()/flush_workqueue() pair is replaced with a per-sb in-flight counter plus pin/unpin/drain helpers so umount no longer serializes against switch activity on unrelated superblocks. Under cgroup writeback churn on a 16 vCPU guest this takes umount latency from ~92-138ms p50 down to ~5-8ms p50 and the cumulative cost of cgroup_writeback_umount() from ~62ms to ~4us per call. The initial race fix is kept separate and minimal so it backports cleanly to stable trees that still queue switches via queue_rcu_work(). - Improve write performance with RWF_DONTCACHE Dirty DONTCACHE pages are now tracked per bdi_writeback so that the writeback flusher can be kicked in a targeted fashion for IOCB_DONTCACHE writes instead of relying on global writeback, and the PG_dropbehind flag is preserved when a folio is split. * tag 'vfs-7.2-rc1.writeback' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: mm: kick writeback flusher for IOCB_DONTCACHE with targeted dirty tracking mm: track DONTCACHE dirty pages per bdi_writeback mm: preserve PG_dropbehind flag during folio split writeback: use a per-sb counter to drain inode wb switches at umount writeback: drop now-unnecessary rcu_barrier() in cgroup_writeback_umount() writeback: fix race between cgroup_writeback_umount() and inode_switch_wbs()

mm/huge_memory: preserve pmd_swp_uffd_wp on device-private PMD downgrade

2026-06-09T01:21:29+00:00

change_non_present_huge_pmd() rewrites a writable device-private PMD swap entry into a readable one without carrying pmd_swp_uffd_wp() across. The PTE-level change_softleaf_pte() does this correctly; mirror that here, matching what copy_huge_pmd() does for the fork path. Without the carry, a plain mprotect() over a UFFD_WP-marked device-private THP strips the bit and the trap is bypassed on swap-in. Link: https://lore.kernel.org/20260529172331.356655-5-kas@kernel.org Fixes: 368076f52ebe ("mm/huge_memory: add device-private THP support to PMD operations") Signed-off-by: Kiryl Shutsemau Reported-by: Sashiko AI review Reviewed-by: Balbir Singh Cc: David Hildenbrand Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Peter Xu Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton