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

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Message-ID: <20240605095727.000023e7@linux.intel.com>
Date: Wed, 5 Jun 2024 09:57:27 -0700
From: Nirmal Patel <nirmal.patel@...ux.intel.com>
To: Jiwei Sun <sjiwei@....com>
Cc: jonathan.derrick@...ux.dev, paul.m.stillwell.jr@...el.com,
 lpieralisi@...nel.org, kw@...ux.com, 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()

On Wed,  5 Jun 2024 20:48:44 +0800
Jiwei Sun <sjiwei@....com> wrote:

> From: Jiwei Sun <sunjw10@...ovo.com>
> 
> 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().
> 
> Signed-off-by: Jiwei Sun <sunjw10@...ovo.com>
> Suggested-by: Adrian Huang <ahuang12@...ovo.com>
> ---
> v3 changes:
>  - Per Paul's comment, move sysfs_remove_link() after
>    pci_stop_root_bus()
> 
> v2 changes:
>  - Add "()" after function names in subject and commit log
>  - Move sysfs_create_link() after vmd_attach_resources()
> 
>  drivers/pci/controller/vmd.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/vmd.c
> b/drivers/pci/controller/vmd.c index 87b7856f375a..4e7fe2e13cac 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -925,6 +925,9 @@ static int vmd_enable_domain(struct vmd_dev *vmd,
> unsigned long features) dev_set_msi_domain(&vmd->bus->dev,
>  				   dev_get_msi_domain(&vmd->dev->dev));
>  
> +	WARN(sysfs_create_link(&vmd->dev->dev.kobj,
> &vmd->bus->dev.kobj,
> +			       "domain"), "Can't create symlink to
> domain\n"); +
>  	vmd_acpi_begin();
>  
>  	pci_scan_child_bus(vmd->bus);
> @@ -964,9 +967,6 @@ static int vmd_enable_domain(struct vmd_dev *vmd,
> unsigned long features) pci_bus_add_devices(vmd->bus);
>  
>  	vmd_acpi_end();
> -
> -	WARN(sysfs_create_link(&vmd->dev->dev.kobj,
> &vmd->bus->dev.kobj,
> -			       "domain"), "Can't create symlink to
> domain\n"); return 0;
>  }
>  
> @@ -1042,8 +1042,8 @@ static void vmd_remove(struct pci_dev *dev)
>  {
>  	struct vmd_dev *vmd = pci_get_drvdata(dev);
>  
> -	sysfs_remove_link(&vmd->dev->dev.kobj, "domain");
>  	pci_stop_root_bus(vmd->bus);
> +	sysfs_remove_link(&vmd->dev->dev.kobj, "domain");
>  	pci_remove_root_bus(vmd->bus);
>  	vmd_cleanup_srcu(vmd);
>  	vmd_detach_resources(vmd);

Reviewed-by: Nirmal Patel <nirmal.patel@...ux.intel.com>

Thanks

-nirmal