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Brian Foster c360004c01 xfs: set max_agbno to allow sparse alloc of last full inode chunk
Sparse inode cluster allocation sets min/max agbno values to avoid
allocating an inode cluster that might map to an invalid inode
chunk. For example, we can't have an inode record mapped to agbno 0
or that extends past the end of a runt AG of misaligned size.

The initial calculation of max_agbno is unnecessarily conservative,
however. This has triggered a corner case allocation failure where a
small runt AG (i.e. 2063 blocks) is mostly full save for an extent
to the EOFS boundary: [2050,13]. max_agbno is set to 2048 in this
case, which happens to be the offset of the last possible valid
inode chunk in the AG. In practice, we should be able to allocate
the 4-block cluster at agbno 2052 to map to the parent inode record
at agbno 2048, but the max_agbno value precludes it.

Note that this can result in filesystem shutdown via dirty trans
cancel on stable kernels prior to commit 9eb775968b ("xfs: walk
all AGs if TRYLOCK passed to xfs_alloc_vextent_iterate_ags") because
the tail AG selection by the allocator sets t_highest_agno on the
transaction. If the inode allocator spins around and finds an inode
chunk with free inodes in an earlier AG, the subsequent dir name
creation path may still fail to allocate due to the AG restriction
and cancel.

To avoid this problem, update the max_agbno calculation to the agbno
prior to the last chunk aligned agbno in the AG. This is not
necessarily the last valid allocation target for a sparse chunk, but
since inode chunks (i.e. records) are chunk aligned and sparse
allocs are cluster sized/aligned, this allows the sb_spino_align
alignment restriction to take over and round down the max effective
agbno to within the last valid inode chunk in the AG.

Note that even though the allocator improvements in the
aforementioned commit seem to avoid this particular dirty trans
cancel situation, the max_agbno logic improvement still applies as
we should be able to allocate from an AG that has been appropriately
selected. The more important target for this patch however are
older/stable kernels prior to this allocator rework/improvement.

Cc: stable@vger.kernel.org # v4.2
Fixes: 56d1115c9b ("xfs: allocate sparse inode chunks on full chunk allocation failure")
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
History 2026-01-13 10:45:55 +01:00
arch Misc fixes: 2025-12-14 06:10:35 +12:00
block block-6.19-20251211 2025-12-12 22:04:18 +12:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
Documentation Misc fixes: 2025-12-14 06:07:09 +12:00
drivers SCSI misc on 20251214 2025-12-14 15:35:35 +12:00
fs
include We have a patch that adds an initial set of tracepoints to the MDS 2025-12-14 15:24:10 +12:00
init Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
io_uring io_uring-6.19-20251211 2025-12-12 22:01:32 +12:00
ipc Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
kernel Fix CPU hotplug callbacks to disable interrupts on UP kernels. 2025-12-14 06:12:46 +12:00
lib Miscellaneous fixes: 2025-12-14 06:04:16 +12:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm There are no significant series in this small merge. Please see the 2025-12-13 20:55:12 +12:00
net We have a patch that adds an initial set of tracepoints to the MDS 2025-12-14 15:24:10 +12:00
rust USB/Thunderbolt changes for 6.19-rc1 2025-12-06 18:42:12 -08:00
samples USB/Thunderbolt changes for 6.19-rc1 2025-12-06 18:42:12 -08:00
scripts There are no significant series in this small merge. Please see the 2025-12-13 20:55:12 +12:00
security Trivial optimization. 2025-12-14 15:21:02 +12:00
sound soundwire updates for 6.19 2025-12-13 16:26:55 +12:00
tools Futex changes for v6.19: 2025-12-10 17:21:30 +09:00
usr initramfs: add gen_init_cpio to hostprogs unconditionally 2025-11-26 21:55:40 +01:00
virt soc: driver updates for 6.19 2025-12-05 17:29:04 -08:00
.clang-format Significant patch series in this merge are as follows: 2025-12-05 13:52:43 -08:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: kbuild: add proc macro library support 2025-11-24 17:15:36 +01:00
.mailmap Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS phy-for-6.19 2025-12-09 06:31:47 +09:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Patch series in this pull request: 2025-12-13 20:35:41 +12:00
Makefile Linux 6.19-rc1 2025-12-14 16:05:07 +12:00
README README: restructure with role-based documentation and guidelines 2025-11-29 08:40:33 -07:00

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


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



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