mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-08-30 11:03:07 -04:00
b90408ef11
Patch series "mm/damon: validate all parameters in the core". DAMON has a number of parameters. Some of the parameters are validated by DAMON, while some are validated by DAMON API callers. Each caller has their own set of parameters that are exposed to users. Hence each caller has their own ways to do the validation. There is no clear lines for the responsibilities. It is confusing and easy to make mistakes at validations. Actually we found a few bugs in the class. Define DAMON core as the place to do all the validations and implement those. damon_set_regions(), damon_start() and damon_commit_ctx() are the three main DAMON core API functions for setup of DAMON parameters. Make the three functions to do safe and holistic parameter checks. The first one is already providing the validation, so changes are only for the last two functions. This might add unnecessary validations for some use cases. The overhead should be negligible as parameters update is expected to only rarely happen. It reduces the number of places to check and fix for bugs of the class from all callers to the single component. The maintenance efficiency gain is obvious. Further cleanup documents and caller code. Make the lines of validation duties clearer. Remove validations that are no more needed owing to the core validations. Patches Sequence ================ Patch 1 implements the core holistic parameters validation for damon_commit_ctx(). Patch 2 extends the validation to damon_start(). Patch 3 removes the duplicated holistic parameters validation in DAMON sysfs interface, which is now embedded into the core layer. Patches 4 and 5 remove duplicated min_region_sz validation in DAMON modules. Patches 6 updates kernel doc to clarify damon_set_regions() is doing the range validation. Patches 7 and 8 remove monitoring target range validations that doesn't necessary thanks to the validation in damon_set_regions(). This patch (of 8): damon_commit_ctx() does its holistic parameter set validation while applying the new parameter in the set one by one. If it finds a parameter is invalid, because some invalid parameters may already be committed (it is called "commit" but not atomic and irreversable), it stops the running DAMON context. The callers of the function therefore have to validate the parameters before calling it. Because the function already embeds holistic validation, DAMON_SYSFS reuses it in a safe way. It creates a test-purpose context that is not running but mimics the running one, and calls damon_commit_ctx() against the test purpose context. If it succeeds, the parameters are considered valid, and a real damon_commit_ctx() call against the running context is made with those. Other callers such as DAMON_RECLAIM and DAMON_LRU_SORT do not expose full parameters to users. For efficiency, they validate only the known set of parameters. The efficiency gain is arguably small and doubtful, though. Meanwhile the maintenance overhead of the multiple different validations is clearly high. We actually found and fixed a few bugs in the class. Update damon_commit_ctx() to embed DAMON_SYSFS' safe and holistic validation approach. Callers can simply call damon_commit_ctx() without worrying if their parameters are invalid. Note that damon_commit_ctx() can still cause an unexpected stop of the running context, if internal memory allocation fails. It is arguably unlikely since those internal allocations are too small to fail, but theoretically possible. It should also be better addressed, but not necessarily a blocker of this small and incremental improvement effort. Link: https://lore.kernel.org/20260705155600.96555-1-sj@kernel.org Link: https://lore.kernel.org/20260705155600.96555-2-sj@kernel.org Signed-off-by: SJ Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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