From e23211aecfc35cf0ddc8aea15d1fd4c82e50eabe Mon Sep 17 00:00:00 2001 From: Jiwei Sun Date: Fri, 14 Mar 2025 12:03:09 +0900 Subject: [PATCH] PCI: vmd: Create domain symlink before pci_bus_add_devices() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit BugLink: https://bugs.launchpad.net/bugs/2102266 [ 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 Link: https://lore.kernel.org/linux-pci/20240605124844.24293-1-sjiwei@163.com Signed-off-by: Jiwei Sun Signed-off-by: Krzysztof Wilczyński [bhelgaas: commit log] Signed-off-by: Bjorn Helgaas Reviewed-by: Nirmal Patel Signed-off-by: Sasha Levin [koichiroden: note that due to the Ubuntu SAUCE (which did not reach upstream): e2b1afd8f92c ("UBUNTU: SAUCE: PCI: vmd: guard device addition and removal"), sysfs_create_link() now added into the critical section] Signed-off-by: Koichiro Den Signed-off-by: Mehmet Basaran --- drivers/pci/controller/vmd.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c index 96a1da7c620d..eba06de5ca6c 100644 --- a/drivers/pci/controller/vmd.c +++ b/drivers/pci/controller/vmd.c @@ -936,6 +936,9 @@ 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); @@ -978,8 +981,6 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features) pci_unlock_rescan_remove(); - WARN(sysfs_create_link(&vmd->dev->dev.kobj, &vmd->bus->dev.kobj, - "domain"), "Can't create symlink to domain\n"); return 0; } @@ -1055,8 +1056,8 @@ 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);