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
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Pull NFS client updates from Trond Myklebust:
"Bugfixes:
- Fix handling of ENOSPC so that if we have to resend writes, they
are written synchronously
- SUNRPC RDMA transport fixes from Chuck
- Several fixes for delegated timestamps in NFSv4.2
- Failure to obtain a directory delegation should not cause stat() to
fail with NFSv4
- Rename was failing to update timestamps when a directory delegation
is held on NFSv4
- Ensure we check rsize/wsize after crossing a NFSv4 filesystem
boundary
- NFSv4/pnfs:
- If the server is down, retry the layout returns on reboot
- Fallback to MDS could result in a short write being incorrectly
logged
Cleanups:
- Use memcpy_and_pad in decode_fh"
* tag 'nfs-for-7.1-1' of git://git.linux-nfs.org/projects/trondmy/linux-nfs: (21 commits)
NFS: Fix RCU dereference of cl_xprt in nfs_compare_super_address
NFS: remove redundant __private attribute from nfs_page_class
NFSv4.2: fix CLONE/COPY attrs in presence of delegated attributes
NFS: fix writeback in presence of errors
nfs: use memcpy_and_pad in decode_fh
NFSv4.1: Apply session size limits on clone path
NFSv4: retry GETATTR if GET_DIR_DELEGATION failed
NFS: fix RENAME attr in presence of directory delegations
pnfs/flexfiles: validate ds_versions_cnt is non-zero
NFS/blocklayout: print each device used for SCSI layouts
xprtrdma: Post receive buffers after RPC completion
xprtrdma: Scale receive batch size with credit window
xprtrdma: Replace rpcrdma_mr_seg with xdr_buf cursor
xprtrdma: Decouple frwr_wp_create from frwr_map
xprtrdma: Close lost-wakeup race in xprt_rdma_alloc_slot
xprtrdma: Avoid 250 ms delay on backlog wakeup
xprtrdma: Close sendctx get/put race that can block a transport
nfs: update inode ctime after removexattr operation
nfs: fix utimensat() for atime with delegated timestamps
NFS: improve "Server wrote zero bytes" error
...
Pull ceph updates from Ilya Dryomov:
"We have a series from Alex which extends CephFS client metrics with
support for per-subvolume data I/O performance and latency tracking
(metadata operations aren't included) and a good variety of fixes and
cleanups across RBD and CephFS"
* tag 'ceph-for-7.1-rc1' of https://github.com/ceph/ceph-client:
ceph: add subvolume metrics collection and reporting
ceph: parse subvolume_id from InodeStat v9 and store in inode
ceph: handle InodeStat v8 versioned field in reply parsing
libceph: Fix slab-out-of-bounds access in auth message processing
rbd: fix null-ptr-deref when device_add_disk() fails
crush: cleanup in crush_do_rule() method
ceph: clear s_cap_reconnect when ceph_pagelist_encode_32() fails
ceph: only d_add() negative dentries when they are unhashed
libceph: update outdated comment in ceph_sock_write_space()
libceph: Remove obsolete session key alignment logic
ceph: fix num_ops off-by-one when crypto allocation fails
libceph: Prevent potential null-ptr-deref in ceph_handle_auth_reply()
The cl_xprt pointer in struct rpc_clnt is marked as __rcu. Accessing
it directly in nfs_compare_super_address() is unsafe and triggers
Sparse warnings.
Fix this by using rcu_dereference() within an RCU read-side critical
section to retrieve the transport pointer. This addresses the sparse
warning and ensures atomic access to the pointer, as the transport
can be updated via transport switching even while the superblock
remains active under sb_lock.
Fixes: 7e3fcf61abde ("nfs: don't share mounts between network namespaces")
Signed-off-by: Sean Chang <seanwascoding@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Pull ntfs updates from Namjae Jeon:
- Fix potential data leakage by zeroing the portion of the straddle
block beyond initialized_size when reading non-resident attributes
- Remove unnecessary zeroing in ntfs_punch_hole() for ranges beyond
initialized_size, as they are already returned as zeros on read
- Fix writable check in ntfs_file_mmap_prepare() to correctly handle
shared mappings using VMA_SHARED_BIT | VMA_MAYWRITE_BIT
- Use page allocation instead of kmemdup() for IOMAP_INLINE data to
ensure page-aligned address and avoid BUG trap in
iomap_inline_data_valid() caused by the page boundary check
- Add a size check before memory allocation in ntfs_attr_readall() and
reject overly large attributes
- Remove unneeded noop_direct_IO from ntfs_aops as it is no longer
required following the FMODE_CAN_ODIRECT flag
- Fix seven static analysis warnings reported by Smatch
* tag 'ntfs-for-7.1-rc1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/ntfs:
ntfs: use page allocation for resident attribute inline data
ntfs: fix mmap_prepare writable check for shared mappings
ntfs: fix potential 32-bit truncation in ntfs_write_cb()
ntfs: fix uninitialized variable in ntfs_map_runlist_nolock
ntfs: delete dead code
ntfs: add missing error code in ntfs_mft_record_alloc()
ntfs: fix uninitialized variables in ntfs_ea_set_wsl_inode()
ntfs: fix uninitialized pointer in ntfs_write_mft_block
ntfs: fix uninitialized variable in ntfs_write_simple_iomap_begin_non_resident
ntfs: remove noop_direct_IO from address_space_operations
ntfs: limit memory allocation in ntfs_attr_readall
ntfs: not zero out range beyond init in punch_hole
ntfs: zero out stale data in straddle block beyond initialized_size
Add complete infrastructure for per-subvolume I/O metrics collection
and reporting to the MDS. This enables administrators to monitor I/O
patterns at the subvolume granularity, which is useful for multi-tenant
CephFS deployments.
This patch adds:
- CEPHFS_FEATURE_SUBVOLUME_METRICS feature flag for MDS negotiation
- CEPH_SUBVOLUME_ID_NONE constant (0) for unknown/unset state
- Red-black tree based metrics tracker for efficient per-subvolume
aggregation with kmem_cache for entry allocations
- Wire format encoding matching the MDS C++ AggregatedIOMetrics struct
- Integration with the existing CLIENT_METRICS message
- Recording of I/O operations from file read/write and writeback paths
- Debugfs interfaces for monitoring (metrics/subvolumes, metrics/metric_features)
Metrics tracked per subvolume include:
- Read/write operation counts
- Read/write byte counts
- Read/write latency sums (for average calculation)
The metrics are periodically sent to the MDS as part of the existing
metrics reporting infrastructure when the MDS advertises support for
the SUBVOLUME_METRICS feature.
CEPH_SUBVOLUME_ID_NONE enforces subvolume_id immutability. Following
the FUSE client convention, 0 means unknown/unset. Once an inode has
a valid (non-zero) subvolume_id, it should not change during the
inode's lifetime.
Signed-off-by: Alex Markuze <amarkuze@redhat.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
The nfs_page_class tracepoint uses a pointer for the 'req' field marked
with the __private attribute. This causes Sparse to complain about
dereferencing a private pointer within the trace ring buffer context,
specifically during the TP_fast_assign() operation.
This fixes a Sparse warning introduced in commit b6ef079fd984 ("nfs:
more in-depth tracing of writepage events") by removing the redundant
__private attribute from the 'req' field.
Reviewed-by: Benjamin Coddington <bcodding@hammerspace.com>
Signed-off-by: Sean Chang <seanwascoding@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Pull 9p updates from Dominique Martinet:
- 9p access flag fix (cannot change access flag since new mount API implem)
- some minor cleanup
* tag '9p-for-7.1-rc1' of https://github.com/martinetd/linux:
9p/trans_xen: replace simple_strto* with kstrtouint
9p/trans_xen: make cleanup idempotent after dataring alloc errors
9p: document missing enum values in kernel-doc comments
9p: fix access mode flags being ORed instead of replaced
9p: fix memory leak in v9fs_init_fs_context error path
The current kmemdup() based allocation for IOMAP_INLINE can result in
inline_data pointer having a non-zero page offset. This causes
iomap_inline_data_valid() to fail the check:
iomap->length <= PAGE_SIZE - offset_in_page(iomap->inline_data)
and triggers the kernel BUG at fs/iomap/buffered-io.c:1061.
This particularly affects workloads with frequent small file access
(e.g. Firefox Nightly profile on NTFS with bind mount) when using the
new ntfs. This fix this by allocating a full page with alloc_page() so that
page_address() always returns a page-aligned address.
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Add support for parsing the subvolume_id field from InodeStat v9 and
storing it in the inode for later use by subvolume metrics tracking.
The subvolume_id identifies which CephFS subvolume an inode belongs to,
enabling per-subvolume I/O metrics collection and reporting.
This patch:
- Adds subvolume_id field to struct ceph_mds_reply_info_in
- Adds i_subvolume_id field to struct ceph_inode_info
- Parses subvolume_id from v9 InodeStat in parse_reply_info_in()
- Adds ceph_inode_set_subvolume() helper to propagate the ID to inodes
- Initializes i_subvolume_id in inode allocation and clears on destroy
Signed-off-by: Alex Markuze <amarkuze@redhat.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
xfstest generic/407 is failing in 2 ways. It detects that after
doing a clone the client does not update it's mtime and it's ctime.
CLONE always sends a GETATTR operation and then calls
nfs_post_op_update_inode() based on the returned attributes.
Because of the delegated attributes the client ignores updating
the mtime. Then also, when delegated attributes are present, for
the change_attr the server replies with the same values as what
the client cached before and thus the generic/407 would flag that.
Instead, make sure we invalidate the blocks attr.
By adding updating delegated attributes in nfs42_copy_dest_done()
both COPY and CLONE would update mtime appropriately.
Fixes: e12912d94137 ("NFSv4: Add support for delegated atime and mtime attributes")
Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Pull SPDX update from Greg KH:
"Here is a single SPDX-like change for 7.1-rc1. It explicitly allows
the use of SPDX-FileCopyrightText which has been used already in many
files.
At the same time, update checkpatch to catch any "non allowed" spdx
identifiers as we don't want to go overboard here.
This has been in linux-next for a long time with no reported problems"
* tag 'spdx-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx:
LICENSES: Explicitly allow SPDX-FileCopyrightText
In xen_9pfs_front_init(), parse the backend version list as comma-separated
tokens with kstrtouint(), keep strict token validation, and explicitly
require protocol version 1 to be present.
This replaces the deprecated simple_strtoul(), improves error reporting
consistency, and avoids partially parsed values in control paths.
Signed-off-by: Yufan Chen <ericterminal@gmail.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Message-ID: <20260324153023.86853-3-ericterminal@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Linus pointed out that checking only VMA_WRITE_BIT is incorrect.
Private writable mappings (MAP_PRIVATE) set VM_WRITE but do not
write back to the filesystem. Also, mappings that can become
writable via mprotect() (VM_MAYWRITE) must be handled.
Use vma_desc_test_all(VMA_SHARED_BIT, VMA_MAYWRITE_BIT) instead,
which matches what other filesystems do.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Add forward-compatible handling for the new versioned field introduced
in InodeStat v8. This patch only skips the field without using it,
preparing for future protocol extensions.
The v8 encoding adds a versioned sub-structure that needs to be properly
decoded and skipped to maintain compatibility with newer MDS versions.
Signed-off-by: Alex Markuze <amarkuze@redhat.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
After running xfstest generic/751, in certain conditions, can have
a writeback IO stuck while experiencing one of the two patterns.
Pattern#1: writeback IO experiences ENOSPC on an offset smaller
than the filesize. Example,
write offset=0 len=4096 how=unstable OK
write offset=8192 len=4096 how=unstable OK
write offset=12288 len=4096 how=unstable ENOSPC
write offset=4096 len=4096 how=unstable ENOSPC
client sends a commit and receives a verifier which is different
from the last successful write. It marks pages dirty and writeback
retries. But it again send writes unstable and gets into the same
pattern, running into the ENOSPC error and sending a commit because
writes were sent at unstable.
Pattern#2: an unstable write followed by a short write and ENOSPC.
write offset=0 len=4096 how=unstable OK
write offset=4096 len=4096 how=unstable returns OK but count=100
write offset=4197 len=3996 how=stable returns ENOSPC
client send a commit and receives a verifier different from
the last unstable write. The same behaviour is retried in a loop.
Instead, this patch proposes to identify those conditions and mark
requests to be done synchronously instead. Previous solution tried
to mark it in the nfs_page, however that's not persistent thus
instead mark it in the nfs_open_context.
Furthermore, the same problem occurs during localio code path so
recognize that IO needs to be done sync in that case as well.
Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Pull char / misc / IIO / and others driver updates from Greg KH:
"Here is the char/misc/iio and other smaller driver subsystem updates
for 7.1-rc1. Lots of stuff in here, all tiny, but relevant for the
different drivers they touch. Major points in here is:
- the usual large set of new IIO drivers and updates for that
subsystem (the large majority of this diffstat)
- lots of comedi driver updates and bugfixes
- coresight driver updates
- interconnect driver updates and additions
- mei driver updates
- binder (both rust and C versions) updates and fixes
- lots of other smaller driver subsystem updates and additions
All of these have been in linux-next for a while with no reported
issues"
* tag 'char-misc-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (405 commits)
coresight: tpdm: fix invalid MMIO access issue
mei: me: add nova lake point H DID
mei: lb: add late binding version 2
mei: bus: add mei_cldev_uuid
w1: ds2490: drop redundant device reference
bus: mhi: host: pci_generic: Add Telit FE912C04 modem support
mei: csc: wake device while reading firmware status
mei: csc: support controller with separate PCI device
mei: convert PCI error to common errno
mei: trace: print return value of pci_cfg_read
mei: me: move trace into firmware status read
mei: fix idle print specifiers
mei: me: use PCI_DEVICE_DATA macro
sonypi: Convert ACPI driver to a platform one
misc: apds990x: fix all kernel-doc warnings
most: usb: Use kzalloc_objs for endpoint address array
hpet: Convert ACPI driver to a platform one
misc: vmw_vmci: Fix spelling mistakes in comments
parport: Remove completed item from to-do list
char: remove unnecessary module_init/exit functions
...