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Nilay Shroff 886f352015 nvme-loop: do not cancel I/O and admin tagset during ctrl reset/shutdown
Cancelling the I/O and admin tagsets during nvme-loop controller reset
or shutdown is unnecessary. The subsequent destruction of the I/O and
admin queues already waits for all in-flight target operations to
complete.

Cancelling the tagsets first also opens a race window. After a request
tag has been cancelled, a late completion from the target may still
arrive before the queues are destroyed. In that case the completion path
may access a request whose tag has already been cancelled or freed,
which can lead to a kernel crash. Please see below the kernel crash
encountered while running blktests nvme/040:

run blktests nvme/040 at 2026-03-08 06:34:27
loop0: detected capacity change from 0 to 2097152
nvmet: adding nsid 1 to subsystem blktests-subsystem-1
nvmet: Created nvm controller 1 for subsystem blktests-subsystem-1 for NQN nqn.2014-08.org.nvmexpress:uuid:0f01fb42-9f7f-4856-b0b3-51e60b8de349.
nvme nvme6: creating 96 I/O queues.
nvme nvme6: new ctrl: "blktests-subsystem-1"
nvme_log_error: 1 callbacks suppressed
block nvme6n1: no usable path - requeuing I/O
nvme6c6n1: Read(0x2) @ LBA 2096384, 128 blocks, Host Aborted Command (sct 0x3 / sc 0x71)
blk_print_req_error: 1 callbacks suppressed
I/O error, dev nvme6c6n1, sector 2096384 op 0x0:(READ) flags 0x2880700 phys_seg 1 prio class 2
block nvme6n1: no usable path - requeuing I/O
Kernel attempted to read user page (236) - exploit attempt? (uid: 0)
BUG: Kernel NULL pointer dereference on read at 0x00000236
Faulting instruction address: 0xc000000000961274
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix  SMP NR_CPUS=2048 NUMA pSeries
Modules linked in: nvme_loop nvme_fabrics loop nvmet null_blk rpadlpar_io rpaphp xsk_diag bonding rfkill nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink pseries_rng dax_pmem vmx_crypto drm drm_panel_orientation_quirks xfs mlx5_core nvme bnx2x sd_mod nd_pmem nd_btt nvme_core sg papr_scm tls libnvdimm ibmvscsi ibmveth scsi_transport_srp nvme_keyring nvme_auth mdio hkdf pseries_wdt dm_mirror dm_region_hash dm_log dm_mod fuse [last unloaded: loop]
CPU: 25 UID: 0 PID: 0 Comm: swapper/25 Kdump: loaded Not tainted 7.0.0-rc3+ #14 PREEMPT
Hardware name: IBM,9043-MRX Power11 (architected) 0x820200 0xf000007 of:IBM,FW1120.00 (RF1120_128) hv:phyp pSeries
NIP:  c000000000961274 LR: c008000009af1808 CTR: c00000000096124c
REGS: c0000007ffc0f910 TRAP: 0300   Not tainted  (7.0.0-rc3+)
MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 22222222  XER: 00000000
CFAR: c008000009af232c DAR: 0000000000000236 DSISR: 40000000 IRQMASK: 0
GPR00: c008000009af17fc c0000007ffc0fbb0 c000000001c78100 c0000000be05cc00
GPR04: 0000000000000001 0000000000000000 0000000000000007 0000000000000000
GPR08: 0000000000000000 0000000000000000 0000000000000002 c008000009af2318
GPR12: c00000000096124c c0000007ffdab880 0000000000000000 0000000000000000
GPR16: 0000000000000010 0000000000000000 0000000000000004 0000000000000000
GPR20: 0000000000000001 c000000002ca2b00 0000000100043bb2 000000000000000a
GPR24: 000000000000000a 0000000000000000 0000000000000000 0000000000000000
GPR28: c000000084021d40 c000000084021d50 c0000000be05cd60 c0000000be05cc00
NIP [c000000000961274] blk_mq_complete_request_remote+0x28/0x2d4
LR [c008000009af1808] nvme_loop_queue_response+0x110/0x290 [nvme_loop]
Call Trace:
 0xc00000000502c640 (unreliable)
 nvme_loop_queue_response+0x104/0x290 [nvme_loop]
 __nvmet_req_complete+0x80/0x498 [nvmet]
 nvmet_req_complete+0x24/0xf8 [nvmet]
 nvmet_bio_done+0x58/0xcc [nvmet]
 bio_endio+0x250/0x390
 blk_update_request+0x2e8/0x68c
 blk_mq_end_request+0x30/0x5c
 lo_complete_rq+0x94/0x110 [loop]
 blk_complete_reqs+0x78/0x98
 handle_softirqs+0x148/0x454
 do_softirq_own_stack+0x3c/0x50
 __irq_exit_rcu+0x18c/0x1b4
 irq_exit+0x1c/0x34
 do_IRQ+0x114/0x278
 hardware_interrupt_common_virt+0x28c/0x290

Since the queue teardown path already guarantees that all target-side
operations have completed, cancelling the tagsets is redundant and
unsafe. So avoid cancelling the I/O and admin tagsets during controller
reset and shutdown.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
2026-03-27 07:35:06 -07:00
arch EFI fixes for v7.0 #2 2026-03-08 12:13:09 -07:00
block block: fix bio_alloc_bioset slowpath GFP handling 2026-03-23 07:58:32 -06:00
certs Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
crypto crypto: remove HKDF library 2026-03-27 07:35:03 -07:00
Documentation nvme: Allow reauth from sysfs 2026-03-27 07:35:03 -07:00
drivers nvme-loop: do not cancel I/O and admin tagset during ctrl reset/shutdown 2026-03-27 07:35:06 -07:00
fs Merge branch 'for-7.1/block-integrity' into for-7.1/block 2026-03-09 14:30:14 -06:00
include nvme: Add the DHCHAP maximum HD IDs 2026-03-27 07:35:05 -07:00
init io_uring-7.0-20260305 2026-03-06 08:31:36 -08:00
io_uring io_uring-7.0-20260305 2026-03-06 08:31:36 -08:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel Make clock_adjtime() syscall timex validation slightly more 2026-03-07 17:09:15 -08:00
lib linux_kselftest-kunit-fixes-7.0-rc3 2026-03-06 12:34:49 -08:00
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 block: remove bdev_nonrot() 2026-03-09 14:30:00 -06:00
net xdp: produce a warning when calculated tailroom is negative 2026-03-05 08:02:05 -08:00
rust linux_kselftest-kunit-fixes-7.0-rc3 2026-03-06 12:34:49 -08:00
samples USB / Thunderbolt changes for 7.0-rc1 2026-02-17 09:36:43 -08:00
scripts kbuild: install-extmod-build: Package resolve_btfids if necessary 2026-02-26 14:49:34 -07:00
security Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
sound ASoC: Fixes for v7.0 2026-03-05 17:22:14 +01:00
tools bpf-fixes 2026-03-07 12:20:37 -08:00
usr kbuild: uapi: drop dependency on CC_CAN_LINK 2026-01-16 15:02:11 -07:00
virt KVM: always define KVM_CAP_SYNC_MMU 2026-02-28 15:31:35 +01:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -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
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.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 linux_kselftest-kunit-fixes-7.0-rc3 2026-03-06 12:34:49 -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 MAINTAINERS: remove Thomas Falcon from IBM ibmvnic 2026-03-05 07:35:45 -08:00
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 hwmon fixes for v7.0-rc3 2026-03-07 08:39:59 -08:00
Makefile Linux 7.0-rc3 2026-03-08 16:56:54 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -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
* 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