From: Jiwei Sun <sunjw10@xxxxxxxxxx>
[ Upstream commit f24c9bfcd423e2b2bb0d198456412f614ec2030a ]
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@xxxxxxxxxx>
Link: https://lore.kernel.org/linux-pci/20240605124844.24293-1-sjiwei@xxxxxxx
Signed-off-by: Jiwei Sun <sunjw10@xxxxxxxxxx>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@xxxxxxxxxx>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Nirmal Patel <nirmal.patel@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 f49001ba96c75..10a078ef4799d 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -798,6 +798,9 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
if (vmd->irq_domain)
dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
+ 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);
@@ -814,9 +817,6 @@ 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;
}
@@ -873,8 +873,8 @@ 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);
--
2.43.0
