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Linus Torvalds 83f1454877 Various ext4 updates for 7.2-rc1:
* A major rework of the fast commit mechanism to avoid lock
   contention and deadlocks.  We also export snapshot statistics
   in /proc/fs/ext4/*/fc_info.
 * Performance optimization for directory hash computation by
   processing input in 4-byte chunks and removing function pointers,
   along with new KUnit tests for directory hash.
 * Cleanups in JBD2 to remove special slabs and use kmalloc() instead.
 * Various bug fixes, including:
    - Early validation of donor superblock in EXT4_IOC_MOVE_EXT to avoid
      cross-fs deadlock
    - Fix for a kernel BUG in ext4_write_inline_data_end under
      data=journal
    - Fix for a NULL dereference in jbd2_journal_dirty_metadata when
      handle is aborted
    - Fix for an underflow in JBD2 fast commit block initialization check
    - Fix for LOGFLUSH shutdown ordering to ensure ordered data writeback
    - Miscellaneous fixes for error path return values and KUnit assertions.
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Merge tag 'ext4_for_linus-7.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 updates from Ted Ts'o:

 - A major rework of the fast commit mechanism to avoid lock contention
   and deadlocks. We also export snapshot statistics in
   /proc/fs/ext4/*/fc_info

 - Performance optimization for directory hash computation by processing
   input in 4-byte chunks and removing function pointers, along with new
   KUnit tests for directory hash

 - Cleanups in JBD2 to remove special slabs and use kmalloc() instead

 - Various bug fixes, including:
     - Early validation of donor superblock in EXT4_IOC_MOVE_EXT to
       avoid cross-fs deadlock
     - Fix for a kernel BUG in ext4_write_inline_data_end under
       data=journal
     - Fix for a NULL dereference in jbd2_journal_dirty_metadata when
       handle is aborted
     - Fix for an underflow in JBD2 fast commit block initialization
       check
     - Fix for LOGFLUSH shutdown ordering to ensure ordered data
       writeback
     - Miscellaneous fixes for error path return values and KUnit
       assertions

* tag 'ext4_for_linus-7.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  ext4: validate donor file superblock early in EXT4_IOC_MOVE_EXT
  ext4: fix kernel BUG in ext4_write_inline_data_end
  ext4: fix ERR_PTR(0) in ext4_mkdir()
  jbd2: remove special jbd2 slabs
  ext4: remove mention of PageWriteback
  ext4: improve str2hashbuf by processing 4-byte chunks and removing function pointers
  ext4: add Kunit coverage for directory hash computation
  ext4: fast commit: export snapshot stats in fc_info
  ext4: fast commit: add lock_updates tracepoint
  ext4: fast commit: avoid i_data_sem by dropping ext4_map_blocks() in snapshots
  ext4: fast commit: avoid self-deadlock in inode snapshotting
  ext4: fast commit: avoid waiting for FC_COMMITTING
  ext4: lockdep: handle i_data_sem subclassing for special inodes
  ext4: fast commit: snapshot inode state before writing log
  jbd2: fix integer underflow in jbd2_journal_initialize_fast_commit()
  ext4: fix fast commit wait/wake bit mapping on 64-bit
  jbd2: check for aborted handle in jbd2_journal_dirty_metadata()
  ext4: Use %pe to print PTR_ERR()
  ext4: fix LOGFLUSH shutdown ordering to allow ordered-mode data writeback
  ext4: replace KUnit tests for memcmp() with KUNIT_ASSERT_MEMEQ()
History 2026-06-18 09:42:02 -07:00
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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