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We must correctly update VMA anonymous page offset state on all VMA operations that would result in it changing, with special attention given to remapping. We cover most cases by simply updating vma_set_range() to do so (with a new anonymous page offset parameter), but also notably must update the merging and mapping logic to propagate this parameter correctly. The remap logic remains the same - we may update the anonymous page offset if the VMA is unfaulted, but now this applies to MAP_PRIVATE file-backed mappings too, so we update the code to reflect this. Note that we use __linear_anon_page_index() upon remap as the VMA may be shared, in order that we update the field consistently regardless of VMA type. Similarly, pass through anon page offset to the merge logic, updating the vma_merge_struct struct to propagate it, and also use __linear_anon_page_index() to obtain the anonymous page index so it can be safely used for both shared and MAP_PRIVATE file-backed mappings. In copy_vma(), the anonymous page offset is updated regardless of whether the mapping is a CoW mapping or not. This is both to keep the anonymous page offset consistent even for non-CoW mappings (it is set so should at least remain correct) and makes the logic cleaner. A self-merge however remains permitted only for mappings which can have a populated vma->anon_vma and do not require alignment on a separate file offset - that is pure anonymous VMAs, so only set can_self_merge if vma_is_anonymous(). Finally, we update insert_vm_struct() to correctly set the anonymous page offset on insertion of a VMA. We simply ensure state is correctly propagated here, so no functional changes are intended. Also update VMA userland tests to reflect this change. Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-9-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Deucher <alexander.deucher@amd.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <baoquan.he@linux.dev> Cc: Barry Song <baohua@kernel.org> Cc: Boris Brezillon <boris.brezillon@collabora.com> Cc: Byungchul Park <byungchul@sk.com> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Chris Li <chrisl@kernel.org> Cc: Christan König <christian.koenig@amd.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Cc: Dave Airlie <airlied@gmail.com> Cc: Dev Jain <dev.jain@arm.com> Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Gregory Price (Meta) <gourry@gourry.net> Cc: Harry Yoo <harry@kernel.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Huang Ray <Ray.Huang@amd.com> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Clark <james.clark@linaro.org> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Janosch Frank <frankja@linux.ibm.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jiri Olsa <jolsa@kernel.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Kairui Song <kasong@tencent.com> Cc: Kees Cook <kees@kernel.org> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Lance Yang <lance.yang@linux.dev> Cc: Liam R. Howlett <liam@infradead.org> Cc: Liviu Dudau <liviu.dudau@arm.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Marc Rutland <mark.rutland@arm.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Matthew Auld <matthew.auld@intel.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Maxime Ripard <mripard@kernel.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Namhyung kim <namhyung@kernel.org> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Nico Pache <npache@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Pedro Falcato <pfalcato@suse.de> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Rik van Riel <riel@surriel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Steven Price <steven.price@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Thomas Zimemrmann <tzimmermann@suse.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: xu xin <xu.xin16@zte.com.cn> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst
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