kernel/git/stable/linux.git/Documentation/mm, branch master

Merge tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-08-27T16:17:06+00:00

Pull more MM updates from Andrew Morton: - "mm/rmap: index MAP_PRIVATE file-backed folios by anonymous pgoff" (Lorenzo Stoakes) Index MAP_PRIVATE file-backed folios by their anonymous page offset to resolve confusion around reverse mapping for zeroed and CoW'd file-backed memory. Use this new VMA anonymous page offset tracking to eliminate index conflicts and lay the foundation for scalable CoW performance improvements. - "promote mapped executable folios after first usage for MGLRU" (Baolin Wang) Make MGLRU's protection of mapped executable file folios more reliable. Follow the classical LRU's logic, promoting mapped executable file folios after their first usage to give executable code a better chance to stay in memory and improve workload performance. - "mm: vmscan: fix node reclaim ignoring swappiness parameter" (Ridong Chen) Fix per-node proactive reclaim interface's ignoring the swappiness parameter when CONFIG_MEMCG is disabled by consolidating sc_swappiness() into a single function that checks proactive_swappiness regardless of kernel configuration. - "mm/vmscan: reduce lru_lock contention via vmstat-derived scan-balance cost" (Usama Arif) Reduce lru_lock contention in the reclaim path by deriving scan-balance costs from vmstat counters rather than lock-acquired producer updates. Read and decay these cost signals on the reclaim side under a dedicated per-lruvec lock, reducing total LRU lock wait time by over 60% without impacting scan throughput. - "zram: fix zram issues reported by sashiko" (Sergey Senozhatsky) Fix two low-risk zram bugs which Sashiko spotted in drive-by review. - "Honor XA_FLAGS_ACCOUNT in xas_split_alloc() and charge to folio's memcg" (Zi Yan) Fix xas_split_alloc() by enabling target folio memcg charging during splits and adding the missing __GFP_ACCOUNT flag for proper XArray node memory accounting. - "selftests/mm: use pattern matching in .gitignore" (Pratyush Mallick) Replace hardcoded binary names in selftests/mm/.gitignore with a generic pattern-matching rule to automatically ignore generated test files and avoid manual updates when adding new tests. - "mm/page_ext: remove pgdat_page_ext_init()" (Sang-Heon Jeon) Make the incompatibility between FLATMEM and NUMA explicit in mm/Kconfig and remove the unused pgdat_page_ext_init() function. - "zram: fix zstd error paths and add parameter validation" (Haoqin Huang) Clean up zram compression backends by removing redundant error cleanup, adding parameter and dictionary validation, auto-prefixing algorithm error logs, and resetting parameters prior to reinitialization. - "zram: fix stale scan bounds after reinitialization" (Longlong Xia) Prevent out-of-bounds slot accesses during concurrent zram resets by moving table scan bound calculations under dev_lock in writeback_store() and read_block_state(). - "add anon mTHP collapse test cases" (Baolin Wang) Extend selftests helper functions to support arbitrary page orders and add new test cases and options for mTHP collapse in khugepaged. - "selftests/mm: Handle unsupported and transient test conditions" (Muhammad Usama Anjum) Update MM selftests to report a SKIP status instead of a failure when required kernel or filesystem features are unsupported, while adding retry logic for transient page migration errors. - "mm/zswap: Fixes and improves the zswap shrink" (Hao Jia) Fix the missing zswap global shrinker when CONFIG_MEMCG is disabled and extend shrink_memcg() to support batch writeback for improved writeback efficiency. - "alloc_tag: introduce IOCTL-based filtering for MAP" (Suren Baghdasaryan) Introduce an IOCTL-based binary interface for memory allocation profiling that enables kernel-side filtering before per-CPU counter aggregation. This eliminates the text-parsing overhead of /proc/allocinfo and provides up to a 20x speedup by transferring only filtered allocation data to userspace. - "better block swap batching and a different take on swap_ops v5" (Christoph Hellwig) Refactor block swap I/O to use swap_iocb for batching instead of single-bio requests and rebase the swap_ops interface, achieving faster swap throughput during kernel builds. - "mm: kmemleak: reduce transient false positives by confirming leaks" (Catalin Marinas) Reduce false-positive kmemleak reports by combining two kmemleak enhancements that add a second confirmation scan and a configurable minimum unreferenced scan count module parameter. - "mm: kmemleak: default min_unref_scans to 2 for verbose kernels" (Breno Leitao) Auto-scanning kernels can generate false-positive memory leak reports on single scans, so this patch defaults min_unref_scans to 2 when CONFIG_DEBUG_KMEMLEAK_VERBOSE is enabled to require a second confirming scan. - "swap_ops updates" (Christoph Hellwig) Batching I/O for synchronous swap devices causes performance regressions and filesystem-based swap suffers from double-indirection overhead. This series resolves both issues by reintroducing per-folio writes for synchronous swap and allowing filesystems to directly export their own swap_ops. - "mm/khugepaged: several cleanups" (Nico Pache) khugepaged accumulated redundant state-checking patterns and outdated comments following mTHP integration. Introduce dedicated helpers for PTE validation and event counting while refreshing the internal documentation. - "maple_tree: lock checking and clean ups" (Liam Howlett) Syzbot reports incorrectly blame memory management exit paths for locking bugs, maple tree erase operations risk allocation failures without gfp flags and internal documentation lacks clarity. Improve lock error detection, update docs, fix race and allocation edge cases and optimize erase allocations using a fallback to GFP_KERNEL | GFP_NOFAIL. * tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (172 commits) selftests/proc: make proc-maps-race work with READ_IMPLIES_EXEC memcg: move LRU size accounting on reparenting instead of copying it mm/vmscan: fix comment logic in balance_pgdat maple_tree: add helper mas_make_walkable() maple_tree: avoid extra gap calculation maple_tree: fix argument name in header maple_tree: change two GFP flags in tests maple_tree: document erase and allocations better maple_tree: avoid mas_erase() and mtree_erase() failures maple_tree: document that erase may use GFP_KERNEL for allocations maple_tree: catch race in mas_alloc_cyclic() maple_tree: add bulk parent set helper maple_tree: micro optimisation of mas_wr_store_type() maple_tree: optimise mas_wr_node_store() when not in rcu mode maple_tree: use prefetched value in mas_wr_store_type() maple_tree: clarify comments on mas_nomem() maple_tree: drop MAPLE_ALLOC_SLOTS maple_tree: drop dead code from mas_extend_spanning_null() maple_tree: documentation fix maple_tree: add write lock checking with lockdep sequence numbers ...

Docs/mm: fix outdated "radix tree" in page_migration

2026-08-25T01:43:23+00:00

Steps 7 and 9 of the migration description still say "radix tree", unlike steps 5 and 11 which already use "i_pages lock". The page cache moved to the XArray at mapping->i_pages long ago. Use "page cache tree" for the two remaining references. Link: https://lore.kernel.org/20260812075739.325441-1-husong@kylinos.cn Signed-off-by: Song Hu Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Randy Dunlap Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Matthew Wilcox Cc: Jan Kara Signed-off-by: Andrew Morton

alloc_tag: add ioctl to /proc/allocinfo

2026-08-25T01:43:12+00:00

Patch series "alloc_tag: introduce IOCTL-based filtering for MAP", v8. Currently, memory allocation profiling data is primarily exposed through /proc/allocinfo. While useful for manual inspection, this text-based interface poses challenges for production monitoring and large-scale analysis: 1. Userspace must parse large amounts of text to extract specific fields. 2. To find specific tags, userspace must read the entire dataset, requiring many context switches and high data copying. 3. The kernel currently aggregates per-CPU counters for every allocation size, even those the user intends to filter out immediately. This series introduces a new IOCTL-based binary interface for allocinfo that supports kernel-side filtering. By allowing the user to specify a filter mask, we significantly reduce the work performed in-kernel and the amount of data transferred to userspace. The IOCTL mechanism was chosen for allocinfo to address the per-CPU counter aggregation bottleneck. A traditional read() operation must report the total allocation count and sizes for every code tag in the system. Doing so requires iterating across all CPUs to sum their per-CPU counters for thousands of tags, which introduces substantial runtime overhead. The IOCTL interface allows userspace to push selective filtering criteria directly into the kernel before the per-CPU counter aggregation. The kernel aggregates per-CPU counters only for a small subset of tags that match the filter. This results in significant performance improvement. Beyond fast filtered retrieval, the IOCTL foundation allows introducing a context capture mechanism in the future to capture the context for specific allocations. Performance measurements were conducted on an Intel Xeon Platinum 8481C (224 CPUs) with caches dropped before each run. The IOCTL mechanism shows a ~20x performance improvement for filtered queries. The kernel avoids the expensive per-CPU counter aggregation (alloc_tag_read) for any tags that fail the initial string or location filters. Scenario 1: Specific File Filtering (arch/x86/events/rapl.c) 1. Traditional (cat /proc/allocinfo | grep): 22ms (sys) 2. IOCTL Interface: 1ms (sys) Scenario 2: Compound Filtering (Filename + Size) 1. Traditional: (cat ... | grep | awk): 21ms (sys) 2. IOCTL Interface: 1ms (sys) Scenario 3: Size-Based Filtering (min_size = 1MB) 1. Traditional: (cat ... | awk): 21ms (sys) 2. IOCTL Interface: 14ms (sys) This patch (of 6): Add the following ioctl commands for /proc/allocinfo file: ALLOCINFO_IOC_CONTENT_ID - gets content identifier which can be used to check whether the file content has changed specifically due to module load/unload. Every time a module is loaded / unloaded, the returned value will be different. By comparing the identifier value at the beginning and at the end of the content retrieval operation, users can validate retrieved information for consistency. ALLOCINFO_IOC_GET_AT - gets the record at the specified position. This is the position of a record in /proc/allocinfo. ALLOCINFO_IOC_GET_NEXT - gets the record next to the last retrieved one. If no records were previously retrieved, returns the first record. Note, function file and module names often have the same prefixes, therefore when filtering for them, we compare the last 64 characters to minimize the chances of name collisions. [akpm@linux-foundation.org: include compat.h, per Suren] Closes: https://lore.kernel.org/oe-kbuild-all/202607091820.qbjlGhKK-lkp@intel.com/ Link: https://lore.kernel.org/cover.1783532853.git.abhishekbapat@google.com Link: https://lore.kernel.org/15596de2607ef13e7c77c6d74763f4ae992ec475.1783532853.git.abhishekbapat@google.com Signed-off-by: Suren Baghdasaryan Signed-off-by: Abhishek Bapat Acked-by: Hao Ge Cc: Jonathan Corbet Cc: Kent Overstreet Cc: Sourav Panda Signed-off-by: Andrew Morton

alloc_tag: expose boot-time compression configuration

2026-08-25T01:43:06+00:00

Currently, userspace has limited visibility into the exact active runtime state of memory allocation profiling and its page extension compression ('sysctl.vm.mem_profiling={0|1|never}[,compressed]'). While reading the sysctl provides basic on/off status, it is currently impossible for userspace to natively determine whether page-tag compression was successfully enabled without scraping dmesg boot logs. Add a new read-only sysctl representing how compression was configured at boot time. Link: https://lore.kernel.org/c795f8089f82841e8a6e00d7ca286da2b23aeb7b.1785950530.git.abhishekbapat@google.com Signed-off-by: Abhishek Bapat Acked-by: Suren Baghdasaryan Cc: Hao Ge Signed-off-by: Andrew Morton

ksm: update comments and docs to reference folio->mapping

2026-08-25T01:43:02+00:00

The KSM code already stores and checks the stable node key via folio->mapping, but the comment in ksm_get_folio() and the reverse mapping documentation in ksm.rst still refer to page->mapping. This is a pure wording update to match the folio-based implementation. No functional change is intended. Link: https://lore.kernel.org/20260805105927.41987-1-hongfu.li@linux.dev Signed-off-by: Hongfu Li Acked-by: David Hildenbrand (Arm) Reviewed-by: Xu Xin Reviewed-by: Dongliang Mu Cc: Alex Shi Cc: Chengming Zhou Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Yanteng Si Signed-off-by: Andrew Morton

Merge tag 'slab-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

2026-08-24T17:58:57+00:00

Pull slab updates from Vlastimil Babka: - Add kfree_rcu_nolock() that can be used from contexts where spinning on a lock might be unsafe, such as a BPF program attached to an arbitrary function, or in NMI context. This complements the existing kfree_nolock() support (Harry Yoo) - Runtime instead of compile-time slabobj_ext sizing. Avoid wasting memory when memory allocation profiling is compiled but not enabled, with initial partial support to also avoid wasting memory for objcg pointers when those are not needed, while profiling is enabled (Vlastimil Babka) - Various non-urgent fixes, cleanups and optimizations (Hao Li, Hongling Zeng, Li RongQing, Li Xiasong, Seongjun Hong, Shengming Hu) * tag 'slab-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: (31 commits) mm/slab, kfence, memcg: completely remove obj_ext for kfence objects mm/slab: stop allocating objcg pointers when unnecessary mm/slab: add cache_ and slab_needs_objcg() helpers mm/slab: stop exporting kvfree_rcu_barrier[_on_cache]() slub_kunit: extend the test for kfree_rcu_nolock() mm/slab: introduce kfree_rcu_nolock() mm/slab: introduce struct kvfree_rcu_head for kvfree_rcu batching mm/slab: reduce slabobj_ext memory with allocation profiling disabled mm/slab: introduce slab_obj_ext_has_codetag() mm/slab: allow kfree_rcu_sheaf() on PREEMPT_RT mm/slab: extend deferred free mechanism to handle rcu sheaves mm/slab: use call_rcu() in unknown context if irqs are enabled mm/slab: handle the !allow_spin case in kfree_rcu_sheaf() mm/slab: change struct slabobj_ext to a union mm/slab: replace slab.stride with obj_exts_in_object mm/slab: abstract slabobj_ext.ref access mm/slab: abstract slabobj_ext.objcg access mm/slab: make slab_obj_ext() determine object index mm: move struct slabobj_ext to mm/slab.h mm/slab: remove objs_per_slab() ...

docs/mm: Physical Memory: remove deferred_split_queue

2026-08-07T01:57:19+00:00

deferred_split_queue was removed from struct pglist_data {} in commit fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru"). Remove its description in doc as well. Link: https://lore.kernel.org/20260721111919.22923-1-zenghui.yu@linux.dev Signed-off-by: Zenghui Yu (Huawei) Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: SJ Park Signed-off-by: Andrew Morton

docs/mm: fix braces

2026-08-07T01:57:09+00:00

Correct typos in mm documentation by balancing parentheses. Link: https://lore.kernel.org/20260629161156.90213-2-manuelebner@mailbox.org Signed-off-by: Manuel Ebner Acked-by: Randy Dunlap Reviewed-by: Lorenzo Stoakes Acked-by: David Hildenbrand (Arm) Reviewed-by: Vishal Moola Reviewed-by: SJ Park Cc: Jonathan Corbet Signed-off-by: Andrew Morton

mm/hmm: add hmm_range_fault_unlocked_timeout() for mmap lock-drop support

2026-08-05T02:18:54+00:00

hmm_range_fault() requires the caller to hold the mmap read lock for the duration of the call. This is incompatible with mappings whose fault handler may release the mmap lock, notably userfaultfd-managed regions, where handle_mm_fault() can return VM_FAULT_RETRY or VM_FAULT_COMPLETED after dropping the lock. Drivers that need to populate device page tables for such mappings have no way to do so today. Add hmm_range_fault_unlocked_timeout() for callers that do not need to hold mmap_lock across any work outside the HMM fault itself. The helper takes mmap_read_lock_killable() internally, calls the common HMM fault implementation, and releases the lock before returning if it is still held. The timeout is specified in jiffies; passing 0 retries indefinitely, while a non-zero timeout makes the helper return -EBUSY when the retry budget expires. The retry deadline is set before refreshing the notifier sequence and acquiring mmap_lock, so contended mmap_lock acquisition is included in the retry budget. After acquiring mmap_lock, the helper also rejects unstable address spaces before walking page tables. When handle_mm_fault() drops mmap_lock, or when the range is invalidated, hmm_range_fault_unlocked_timeout() refreshes range->notifier_seq and retries the walk internally. If the lock was dropped, the retry deadline is also restarted because a lock-dropping fault handler made progress. Ordinary -EBUSY retries keep the existing deadline, preserving the caller's timeout policy for repeated mmu-notifier invalidations. The caller only needs to perform the usual post-success mmu_interval_read_retry() check while holding its update lock before consuming the pfns. If mmap_lock acquisition is interrupted or a fatal signal is pending during retry handling, -EINTR is returned instead. The common implementation conditionally sets FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_KILLABLE only for hmm_range_fault_unlocked_timeout(). The existing hmm_range_fault() path still passes no locked state, does not allow handle_mm_fault() to drop mmap_lock, and remains a thin wrapper preserving the existing API contract for current callers. The previous refactor that moved page fault handling out of the page-table walk callbacks is what makes this change small. Faults now run after walk_page_range() has unwound, with only mmap_lock held, so dropping it does not interact with the walker's pte spinlock or hugetlb_vma_lock. Hugetlb regions therefore participate in the unlocked path uniformly with PTE- and PMD-level mappings; no special case is required. Documentation/mm/hmm.rst is updated with a description of the new API and the recommended caller pattern. Link: https://lore.kernel.org/20260723-hmm-v10-v11-2-c55b003a4b61@gmail.com Signed-off-by: Stanislav Kinsburskii Cc: Danilo Krummrich Cc: Dave Airlie Cc: David Hildenbrand Cc: Dexuan Cui Cc: Haiyang Zhang Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: K. Y. Srinivasan Cc: Leon Romanovsky Cc: Liam R. Howlett Cc: Lizhi Hou Cc: Long Li Cc: Lorenzo Stoakes Cc: Lyude Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Michal Hocko Cc: Mike Rapoport Cc: Oded Gabbay Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Thomas Zimemrmann Cc: Vlastimil Babka Cc: Wei Liu Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: document weight sysfs file

2026-08-05T02:18:53+00:00

Update DAMON usage document for newly added probe weight file. Link: https://lore.kernel.org/20260710134651.18084-19-sj@kernel.org Signed-off-by: SJ Park Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton