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

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Message-ID: <20240711161246.GA285252@bhelgaas>
Date: Thu, 11 Jul 2024 11:12:46 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Jiwei Sun <sjiwei@....com>
Cc: nirmal.patel@...ux.intel.com, 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 Thu, Jul 11, 2024 at 09:32:46AM +0800, Jiwei Sun wrote:
> 
> On 7/11/24 06:16, Bjorn Helgaas wrote:
> > [-cc Pawel, Alexey, Tomasz, which all bounced]
> > 
> > On Wed, Jul 10, 2024 at 09:29:25PM +0800, Jiwei Sun wrote:
> >> On 7/10/24 04:59, Bjorn Helgaas wrote:
> >>> [+cc Pawel, Alexey, Tomasz for mdadm history]
> >>> On Wed, Jun 05, 2024 at 08:48:44PM +0800, Jiwei Sun 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.
> >>>
> >>> I guess the root filesystem must be on a RAID device, and it's the
> >>> failure to assemble that RAID device that prevents OS boot?  The
> >>> messages are just details about why the assembly failed?
> >>
> >> Yes, you are right, in our test environment, we installed the SLES15SP6
> >> on a VROC RAID 1 device which is set up by two NVME hard drivers. And
> >> there is also a hardware RAID kit on the motherboard with other two NVME 
> >> hard drivers.
> > 
> > OK, thanks for all the details.  What would you think of updating the
> > commit log like this?
> 
> Thanks, I think this commit log is clearer than before. Do I need to 
> send another v4 patch for the changes?

No need, if you think it's OK, I can update the commit log locally.

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