linux-kernel - Re: [PATCH v3] PCI: vmd: Create domain symlink before pci_bus_add

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Message-ID: <20240706032232.GG1195499@rocinante>
Date: Sat, 6 Jul 2024 12:22:32 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Jiwei Sun <sjiwei@....com>
Cc: nirmal.patel@...ux.intel.com, jonathan.derrick@...ux.dev,
	paul.m.stillwell.jr@...el.com, lpieralisi@...nel.org,
	robh@...nel.org, bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, sunjw10@...ovo.com,
	ahuang12@...ovo.com
Subject: Re: [PATCH v3] PCI: vmd: Create domain symlink before
 pci_bus_add_devices()

Hello,

> During booting into the kernel, the following error message appears:
> 
>   (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, the udevd executes
> some rule scripts by invoking mdadm command to detect if there is a
> mdraid associated with this NVMe disk. The mdadm determines if one
> NVMe devce is connected to a particular VMD domain by checking the
> domain symlink. Here is the root cause:
> 
> 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 the domain
>     ...                                            symlink; 2) Find the
>     ...                                            domain symlink from
>     ...                                            vmd sysfs; 3) The
>     ...                                            domain symlink is not
>     ...                                            created yet, failed
>   sysfs_create_link
>   : create domain symlink
> 
> sysfs_create_link() is invoked at the end of vmd_enable_domain().
> However, this implementation introduces a timing issue, where mdadm
> might fail to retrieve the vmd symlink path because the symlink has not
> been created yet.
> 
> Fix the issue by creating VMD domain symlinks before invoking
> pci_bus_add_devices().

Applied to vmd, thank you!

[1/1] PCI: vmd: Create domain symlink before pci_bus_add_devices()
      https://git.kernel.org/pci/pci/c/7a13782e6150

	Krzysztof