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Jiwei Sun db7d50a5d7 PCI: vmd: Create domain symlink before pci_bus_add_devices() 
[ Upstream commit f24c9bfcd4 ]

The vmd driver creates a "domain" symlink in sysfs for each VMD bridge.
Previously this symlink was created after pci_bus_add_devices() added
devices below the VMD bridge and emitted udev events to announce them to
userspace.

This led to a race between userspace consumers of the udev events and the
kernel creation of the symlink.  One such consumer is mdadm, which
assembles block devices into a RAID array, and for devices below a VMD
bridge, mdadm depends on the "domain" symlink.

If mdadm loses the race, it may be unable to assemble a RAID array, which
may cause a boot failure or other issues, with complaints like this:

  (udev-worker)[2149]: nvme1n1: '/sbin/mdadm -I /dev/nvme1n1'(err) 'mdadm: Unable to get real path for '/sys/bus/pci/drivers/vmd/0000:c7:00.5/domain/device''
  (udev-worker)[2149]: nvme1n1: '/sbin/mdadm -I /dev/nvme1n1'(err) 'mdadm: /dev/nvme1n1 is not attached to Intel(R) RAID controller.'
  (udev-worker)[2149]: nvme1n1: '/sbin/mdadm -I /dev/nvme1n1'(err) 'mdadm: No OROM/EFI properties for /dev/nvme1n1'
  (udev-worker)[2149]: nvme1n1: '/sbin/mdadm -I /dev/nvme1n1'(err) 'mdadm: no RAID superblock on /dev/nvme1n1.'
  (udev-worker)[2149]: nvme1n1: Process '/sbin/mdadm -I /dev/nvme1n1' failed with exit code 1.

This symptom prevents the OS from booting successfully.

After a NVMe disk is probed/added by the nvme driver, udevd invokes mdadm
to detect if there is a mdraid associated with this NVMe disk, and mdadm
determines if a NVMe device is connected to a particular VMD domain by
checking the "domain" symlink. For example:

  Thread A                   Thread B             Thread mdadm
  vmd_enable_domain
    pci_bus_add_devices
      __driver_probe_device
       ...
       work_on_cpu
         schedule_work_on
         : wakeup Thread B
                             nvme_probe
                             : wakeup scan_work
                               to scan nvme disk
                               and add nvme disk
                               then wakeup udevd
                                                  : udevd executes
                                                    mdadm command
         flush_work                               main
         : wait for nvme_probe done                ...
      __driver_probe_device                        find_driver_devices
      : probe next nvme device                     : 1) Detect domain symlink
      ...                                            2) Find domain symlink
      ...                                               from vmd sysfs
      ...                                            3) Domain symlink not
      ...                                               created yet; failed
    sysfs_create_link
    : create domain symlink

Create the VMD "domain" symlink before invoking pci_bus_add_devices() to
avoid this race.

Suggested-by: Adrian Huang <ahuang12@lenovo.com>
Link: https://lore.kernel.org/linux-pci/20240605124844.24293-1-sjiwei@163.com
Signed-off-by: Jiwei Sun <sunjw10@lenovo.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Nirmal Patel <nirmal.patel@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-12-27 13:58:41 +01:00
arch x86/xen: remove hypercall page 2024-12-19 18:11:36 +01:00
block blk-iocost: Avoid using clamp() on inuse in __propagate_weights() 2024-12-19 18:11:34 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: pcrypt - Call crypto layer directly when padata_do_parallel() return -EBUSY 2024-12-09 10:31:48 +01:00
Documentation Documentation: PM: Clarify pm_runtime_resume_and_get() return value 2024-12-19 18:11:30 +01:00
drivers PCI: vmd: Create domain symlink before pci_bus_add_devices() 2024-12-27 13:58:41 +01:00
fs xfs: only run precommits once per transaction object 2024-12-19 18:11:25 +01:00
include x86/static-call: fix 32-bit build 2024-12-19 18:11:37 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-09 10:32:46 +01:00
io_uring io_uring/tctx: work around xa_store() allocation error issue 2024-12-14 20:00:17 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel x86/static-call: provide a way to do very early static-call updates 2024-12-19 18:11:36 +01:00
lib lib: stackinit: hide never-taken branch from compiler 2024-12-14 19:59:57 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/damon/vaddr: fix issue in damon_va_evenly_split_region() 2024-12-14 20:00:21 +01:00
net net: sched: fix ordering of qlen adjustment 2024-12-27 13:58:41 +01:00
rust rust: macros: fix documentation of the paste! macro 2024-12-09 10:32:25 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 20:00:03 +01:00
scripts setlocalversion: work around "git describe" performance 2024-12-14 20:00:17 +01:00
security apparmor: test: Fix memory leak for aa_unpack_strdup() 2024-12-09 10:32:45 +01:00
sound ALSA: usb-audio: Fix a DMA to stack memory bug 2024-12-19 18:11:37 +01:00
tools objtool/x86: allow syscall instruction 2024-12-19 18:11:36 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.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 USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.67 2024-12-19 18:11:37 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.