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Christian Brauner 6e75f35786
Merge patch series "fs: Fix missed inode write during fsync"
Jan Kara <jack@suse.cz> says:

The series strives to make sure sync_inode_metadata() ->
writeback_single_inode() will end up to properly persisting not only the inode
but also all metadata associated with the inode.  This is beneficial for
several reasons:

1) This removes the need for separate mmb_fsync() implementations. Filesystems
can just use simple_fsync().

2) This makes sure all metadata is written for IS_SYNC / IS_DIRSYNC inodes.
Currently most filesystems just write inode itself.

3) This fixes races when multiple fsyncs race for a while where mmb_sync()
could return before all buffers were really persisted (now I_SYNC state flag
properly serializes everything).

To be able to achieve this we add new .sync_inode_metadata superblock operation
which gets called from __writeback_single_inode() and new I_METADATA_WRITEBACK
state flag (putting everything into .write_inode is possible but it looked too
ugly so I've decided for the new operation).

This scheme with I_METADATA_WRITEBACK state flag also fixes the problem that
when WB_SYNC_NONE writeback happened between write(2) and fsync(2), fsync(2)
would fail to properly persist the inode. Note that this problem isn't specific
to filesystems using the generic metadata bh tracking. This patch set doesn't
fix such filesystems as it is already big enough but the universality of this
problem among simple filesystems is another reason why I've chosen the new
superblock operation instead of trying to somehow hack up metadata bh tracking
infrastructure.

* patches from https://patch.msgid.link/20260727101509.21667-1-jack@suse.cz:
  vfs: Remove mmb_fsync()
  fat: Replace fat_sync_inode() with sync_inode_metadata()
  fat: Fix missed inode writeback during fsync(2)
  ext4: Fix data integrity writeout issues in nojournal mode
  minix: Fix data integrity writeout issues
  bfs: Fix data integrity writeout issues
  udf: Fold udf_update_inode() into udf_write_inode()
  udf: Use sync_inode_metadata() in udf_evict_inode()
  udf: Drop udf_sync_inode()
  udf: Use sync_inode_metadata() to writeout IS_SYNC inode
  udf: Fix data integrity writeout issues
  ext2: Fix data integrity writeout issues
  ext2: Avoid unnecessary inode buffer writeback for sync(2)
  ext2: Drop __ext2_write_inode()
  ext2: Fix lost inode updates for IS_SYNC inodes
  fs: Provide way for filesystem to wait for metadata writeback
  ext4: Allocate mapping_metadata_bhs struct on demand
  fs: Fix missed inode writeback when racing with __writeback_single_inode
  fs: Fix possible UAF in mark_buffer_write_io_error()
  affs: Drop support for metadata bh tracking

Link: https://patch.msgid.link/20260727101509.21667-1-jack@suse.cz
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
History 2026-07-27 16:25:37 +02:00
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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