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
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1444589
3
929
Clone this repository
https://tangled.org/tjh.dev/kernel
https://tangled.org/did:plc:65gha4t3avpfpzmvpbwovss7/kernel
git@gordian.tjh.dev:tjh.dev/kernel
git@gordian.tjh.dev:did:plc:65gha4t3avpfpzmvpbwovss7/kernel
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
Pull turbostat fix from Len Brown:
"Fix a recent AMD regression due to errant code cleanup"
* tag 'turbostat-2026.02.14-AMD-RAPL-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux:
tools/power turbostat: Fix AMD RAPL regression
Pull turbostat updates from Len Brown:
- Add L2 statistics columns for recent Intel processors:
L2MRPS = L2 Cache M-References Per Second
L2%hit = L2 Cache Hit %
- Sort work and output by cpu# rather than core#
- Minor features and fixes
* tag 'turbostat-2026.02.14' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux: (23 commits)
tools/power turbostat: version 2026.02.14
tools/power turbostat: Fix and document --header_iterations
tools/power turbostat: Use strtoul() for iteration parsing
tools/power turbostat: Favor cpu# over core#
tools/power turbostat: Expunge logical_cpu_id
tools/power turbostat: Enhance HT enumeration
tools/power turbostat: Simplify global core_id calculation
tools/power turbostat: Unify even/odd/average counter referencing
tools/power turbostat: Allocate average counters dynamically
tools/power turbostat: Delete core_data.core_id
tools/power turbostat: Rename physical_core_id to core_id
tools/power turbostat: Cleanup package_id
tools/power turbostat: Cleanup internal use of "base_cpu"
tools/power turbostat: Add L2 cache statistics
tools/power turbostat: Remove redundant newlines from err(3) strings
tools/power turbostat: Allow more use of is_hybrid flag
tools/power turbostat: Rename "LLCkRPS" column to "LLCMRPS"
tools/power turbostat.8: Document the "--force" option
tools/power turbostat: Harden against unexpected values
tools/power turbostat: Dump hypervisor name
...
turbostat.c:8688: rapl_perf_init: Assertion `next_domain < num_domains' failed.
Two recent cleanup patches that were not supposed to change anything
broke the core_id code needed for AMD RAPL initialization:
commit 070e92361eec ("tools/power turbostat: Enhance HT enumeration")
commit ddf60e38ca04 ("tools/power turbostat: Simplify global core_id calculation")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
Pull ntfs3 updates from Konstantin Komarov:
"New code:
- improve readahead for bitmap initialization and large directory scans
- fsync files by syncing parent inodes
- drop of preallocated clusters for sparse and compressed files
- zero-fill folios beyond i_valid in ntfs_read_folio()
- implement llseek SEEK_DATA/SEEK_HOLE by scanning data runs
- implement iomap-based file operations
- allow explicit boolean acl/prealloc mount options
- fall-through between switch labels
- delayed-allocation (delalloc) support
Fixes:
- check return value of indx_find to avoid infinite loop
- initialize new folios before use
- infinite loop in attr_load_runs_range on inconsistent metadata
- infinite loop triggered by zero-sized ATTR_LIST
- ntfs_mount_options leak in ntfs_fill_super()
- deadlock in ni_read_folio_cmpr
- circular locking dependency in run_unpack_ex
- prevent infinite loops caused by the next valid being the same
- restore NULL folio initialization in ntfs_writepages()
- slab-out-of-bounds read in DeleteIndexEntryRoot
Updates:
- allow readdir() to finish after directory mutations without rewinddir()
- handle attr_set_size() errors when truncating files
- make ntfs_writeback_ops static
- refactor duplicate kmemdup pattern in do_action()
- avoid calling run_get_entry() when run == NULL in ntfs_read_run_nb_ra()
Replaced:
- use wait_on_buffer() directly
- rename ni_readpage_cmpr into ni_read_folio_cmpr"
* tag 'ntfs3_for_7.0' of https://github.com/Paragon-Software-Group/linux-ntfs3: (26 commits)
fs/ntfs3: add delayed-allocation (delalloc) support
fs/ntfs3: avoid calling run_get_entry() when run == NULL in ntfs_read_run_nb_ra()
fs/ntfs3: add fall-through between switch labels
fs/ntfs3: allow explicit boolean acl/prealloc mount options
fs/ntfs3: Fix slab-out-of-bounds read in DeleteIndexEntryRoot
ntfs3: Restore NULL folio initialization in ntfs_writepages()
ntfs3: Refactor duplicate kmemdup pattern in do_action()
fs/ntfs3: prevent infinite loops caused by the next valid being the same
fs/ntfs3: make ntfs_writeback_ops static
ntfs3: fix circular locking dependency in run_unpack_ex
fs/ntfs3: implement iomap-based file operations
fs/ntfs3: fix deadlock in ni_read_folio_cmpr
fs/ntfs3: implement llseek SEEK_DATA/SEEK_HOLE by scanning data runs
fs/ntfs3: zero-fill folios beyond i_valid in ntfs_read_folio()
fs/ntfs3: handle attr_set_size() errors when truncating files
fs/ntfs3: drop preallocated clusters for sparse and compressed files
fs/ntfs3: fsync files by syncing parent inodes
fs/ntfs3: fix ntfs_mount_options leak in ntfs_fill_super()
fs/ntfs3: allow readdir() to finish after directory mutations without rewinddir()
fs/ntfs3: improve readahead for bitmap initialization and large directory scans
...
Since release 2025.12.02:
Add L2 statistics columns for recent Intel processors:
L2MRPS = L2 Cache M-References Per Second
L2%hit = L2 Cache Hit %
Sort work and output by cpu# rather than core#
This commit:
Version number and white space (indent -l160)
No functional change.
Signed-off-by: Len Brown <len.brown@intel.com>
Pull ceph updates from Ilya Dryomov:
"This adds support for the upcoming aes256k key type in CephX that is
based on Kerberos 5 and brings a bunch of assorted CephFS fixes from
Ethan and Sam. One of Sam's patches in particular undoes a change in
the fscrypt area that had an inadvertent side effect of making CephFS
behave as if mounted with wsize=4096 and leading to the corresponding
degradation in performance, especially for sequential writes"
* tag 'ceph-for-7.0-rc1' of https://github.com/ceph/ceph-client:
ceph: assert loop invariants in ceph_writepages_start()
ceph: remove error return from ceph_process_folio_batch()
ceph: fix write storm on fscrypted files
ceph: do not propagate page array emplacement errors as batch errors
ceph: supply snapshot context in ceph_uninline_data()
ceph: supply snapshot context in ceph_zero_partial_object()
libceph: adapt ceph_x_challenge_blob hashing and msgr1 message signing
libceph: add support for CEPH_CRYPTO_AES256KRB5
libceph: introduce ceph_crypto_key_prepare()
libceph: generalize ceph_x_encrypt_offset() and ceph_x_encrypt_buflen()
libceph: define and enforce CEPH_MAX_KEY_LEN
This patch implements delayed allocation (delalloc) in ntfs3 driver.
It introduces an in-memory delayed-runlist (run_da) and the helpers to
track, reserve and later convert those delayed reservations into real
clusters at writeback time. The change keeps on-disk formats untouched and
focuses on pagecache integration, correctness and safe interaction with
fallocate, truncate, and dio/iomap paths.
Key points:
- add run_da (delay-allocated run tree) and bookkeeping for delayed clusters.
- mark ranges as delalloc (DELALLOC_LCN) instead of immediately allocating.
Actual allocation performed later (writeback / attr_set_size_ex / explicit
flush paths).
- direct i/o / iomap paths updated to avoid dio collisions with
delalloc: dio falls back or forces allocation of delayed blocks before
proceeding.
- punch/collapse/truncate/fallocate check and cancel delay-alloc reservations.
Sparse/compressed files handled specially.
- free-space checks updated (ntfs_check_free_space) to account for reserved
delalloc clusters and MFT record budgeting.
- delayed allocations are committed on last writer (file release) and on
explicit allocation flush paths.
Tested-by: syzbot@syzkaller.appspotmail.com
Reported-by: syzbot+2bd8e813c7f767aa9bb1@syzkaller.appspotmail.com
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
The "header_iterations" option is commonly used to de-clutter
the screen of redundant header label rows in an interactive session:
Eg. every 10 rows:
$ sudo turbostat --header_iterations 10 -S -q -i 1
But --header_iterations was missing from turbostat.8
Also turbostat help advertised the "-N" short option
that did not actually work:
$ turbostat --help
-N, --header_iterations num
print header every num iterations
Repair "-N"
Document "--header_iterations" on turbostat.8
Signed-off-by: Len Brown <len.brown@intel.com>
Pull overlayfs update from Amir Goldstein:
"Relax the semantics of uuid=off to cater to a use case of overlayfs
lower layers on btrfs clones, whose UUID are ephemeral and an upper
layer on a different filesystem"
* tag 'ovl-update-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs:
ovl: relax requirement for uuid=off,index=on
If `locked_pages` is zero, the page array must not be allocated:
ceph_process_folio_batch() uses `locked_pages` to decide when to
allocate `pages`, and redundant allocations trigger
ceph_allocate_page_array()'s BUG_ON(), resulting in a worker oops (and
writeback stall) or even a kernel panic. Consequently, the main loop in
ceph_writepages_start() assumes that the lifetime of `pages` is confined
to a single iteration.
This expectation is currently not clear enough, as evidenced by the
recent patch which fixed an oops caused by `pages` persisting into
the next loop iteration:
- "ceph: do not propagate page array emplacement errors as batch errors"
Use an explicit BUG_ON() at the top of the loop to assert the loop's
preexisting expectation that `pages` is cleaned up by the previous
iteration. Because this is closely tied to `locked_pages`, also make it
the previous iteration's responsibility to guarantee its reset, and
verify with a second new BUG_ON() instead of handling (and masking)
failures to do so.
This patch does not change invariants, behavior, or failure modes.
The added BUG_ON() lines catch conditions that would already trigger oops,
but do so earlier for easier debugging and programmer clarity.
Signed-off-by: Sam Edwards <CFSworks@gmail.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
When ntfs_read_run_nb_ra() is invoked with run == NULL the code later
assumes run is valid and may call run_get_entry(NULL, ...), and also
uses clen/idx without initializing them. Smatch reported uninitialized
variable warnings and this can lead to undefined behaviour. This patch
fixes it.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202512230646.v5hrYXL0-lkp@intel.com/
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Replace strtod() with strtoul() and check errno for -n/-N options, since
num_iterations and header_iterations are unsigned long counters. Reject
zero and conversion errors; negative inputs wrap to large positive values
per standard unsigned semantics.
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Pull smb client fixes from Steve French:
- Fix three potential double free vulnerabilities
- Fix data corruption due to racy lease checks
- Enforce SMB1 signing verification checks
- Fix invalid mount option parsing
- Remove unneeded tracepoint
- Various minor error code corrections
- Minor cleanup
* tag 'v7.0-rc-part2-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6:
smb: client: terminate session upon failed client required signing
cifs: some missing initializations on replay
cifs: remove unnecessary tracing after put tcon
cifs: update internal module version number
smb: client: fix data corruption due to racy lease checks
smb/client: move NT_STATUS_MORE_ENTRIES
smb/client: rename to NT_ERROR_INVALID_DATATYPE
smb/client: rename to NT_STATUS_SOME_NOT_MAPPED
smb/client: map NT_STATUS_PRIVILEGE_NOT_HELD
smb/client: map NT_STATUS_MORE_PROCESSING_REQUIRED
smb/client: map NT_STATUS_BUFFER_OVERFLOW
smb/client: map NT_STATUS_NOTIFY_ENUM_DIR
cifs: SMB1 split: Remove duplicate include of cifs_debug.h
smb: client: fix regression with mount options parsing
uuid=off,index=on required that all upper/lower directories are on the
same filesystem.
Relax the requirement so that only all the lower directories need to be
on the same filesystem.
Reported-by: André Almeida <andrealmeid@igalia.com>
Link: https://lore.kernel.org/r/20260114-tonyk-get_disk_uuid-v1-3-e6a319e25d57@igalia.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Following an earlier commit, ceph_process_folio_batch() no longer
returns errors because the writeback loop cannot handle them.
Since this function already indicates failure to lock any pages by
leaving `ceph_wbc.locked_pages == 0`, and the writeback loop has no way
to handle abandonment of a locked batch, change the return type of
ceph_process_folio_batch() to `void` and remove the pathological goto in
the writeback loop. The lack of a return code emphasizes that
ceph_process_folio_batch() is designed to be abort-free: that is, once
it commits a folio for writeback, it will not later abandon it or
propagate an error for that folio. Any future changes requiring "abort"
logic should follow this invariant by cleaning up its array and
resetting ceph_wbc.locked_pages appropriately.
Signed-off-by: Sam Edwards <CFSworks@gmail.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Add fall-through to fix the warning in ntfs_fs_parse_param().
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202602041402.uojBz5QY-lkp@intel.com/
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
README