Hi everyone,

I have a udev rule file that contains a singular rule:

SUBSYSTEM=="block", ACTION=="add|change", ENV{ID_VENDOR}=="*Google*", ENV{DEVTYPE}=="disk", ATTR{queue/scheduler}:="noop"

When I use a Google Cloud instance and boot it, things work as expected and /dev/sda (a persistent disk) uses the noop scheduler. If the instance also has a Local SSD type disk, however, the change in scheduler is not applied. This is a bit academic, because the Local SSD device uses noop by default (somehow, I don’t see any udev rules for setting this outside of my own). But, for instance, if I set the scheduler in the udev rules to “cfq,” at boot, /dev/sda will use cfq and /dev/sdb will use noop.

If I run udevadm trigger after boot, then /dev/sdb will use cfq. So, it appears that at boot time, for some reason, my scheduler is not being applied to /dev/sdb.

I’ve tried a handful of things:

- changing the order of my udev rule file: I’ve tried 10-, 90-, and 99- prefixes. My rule file is in /etc/udev/rules.d/. - using ATTR{queue/scheduler}:="noop" and ATTR{queue/scheduler}="noop" (both the = and := operator) - searching the internet for all kinds of variations on “udev rule not applying at boot”

but so far, I’ve come up empty-handed. The only thing I can think of is that I am hitting some sort of race condition and udev is unable to set the ATTR in /sys, but I’m not sure how I can confirm this.

Below are dumps from udevadm of the block devices, /dev/sda (a Google Cloud persistent disk that is my root partition) and /dev/sdb (a Google Cloud ephemeral disk [local SSD] that is mounted at /local-ssd).

Thanks in advance for any assistance!

Nick

# udevadm info -q all -a /dev/sda

looking at device '/devices/pci0000:00/0000:00:03.0/virtio0/host0/target0:0:1/0:0:1:0/block/sda': KERNEL=="sda" SUBSYSTEM=="block" DRIVER=="" ATTR{ro}=="0" ATTR{size}=="104857600" ATTR{stat}==" 14877 938 923845 15717 2732 310 82984 4328 0 9685 20033" ATTR{range}=="16" ATTR{discard_alignment}=="0" ATTR{events}=="" ATTR{ext_range}=="256" ATTR{events_poll_msecs}=="-1" ATTR{alignment_offset}=="0" ATTR{badblocks}=="" ATTR{inflight}==" 0 0" ATTR{removable}=="0" ATTR{capability}=="50" ATTR{events_async}==""

looking at parent device '/devices/pci0000:00/0000:00:03.0/virtio0/host0/target0:0:1/0:0:1:0': KERNELS=="0:0:1:0" SUBSYSTEMS=="scsi" DRIVERS=="sd" ATTRS{rev}=="1 " ATTRS{type}=="0" ATTRS{scsi_level}=="7" ATTRS{model}=="PersistentDisk " ATTRS{state}=="running" ATTRS{unpriv_sgio}=="0" ATTRS{queue_type}=="none" ATTRS{iodone_cnt}=="0x478f" ATTRS{iorequest_cnt}=="0x478f" ATTRS{device_busy}=="0" ATTRS{evt_capacity_change_reported}=="0" ATTRS{timeout}=="30" ATTRS{evt_media_change}=="0" ATTRS{ioerr_cnt}=="0x0" ATTRS{queue_depth}=="256" ATTRS{vendor}=="Google " ATTRS{evt_soft_threshold_reached}=="0" ATTRS{device_blocked}=="0" ATTRS{evt_mode_parameter_change_reported}=="0" ATTRS{evt_lun_change_reported}=="0" ATTRS{evt_inquiry_change_reported}=="0" ATTRS{dh_state}=="detached" ATTRS{iocounterbits}=="32" ATTRS{inquiry}=="" ATTRS{vpd_pg80}=="" ATTRS{vpd_pg83}=="" ATTRS{eh_timeout}=="10"

looking at parent device '/devices/pci0000:00/0000:00:03.0/virtio0/host0/target0:0:1': KERNELS=="target0:0:1" SUBSYSTEMS=="scsi" DRIVERS==""

looking at parent device '/devices/pci0000:00/0000:00:03.0/virtio0/host0': KERNELS=="host0" SUBSYSTEMS=="scsi" DRIVERS==""

looking at parent device '/devices/pci0000:00/0000:00:03.0/virtio0': KERNELS=="virtio0" SUBSYSTEMS=="virtio" DRIVERS=="virtio_scsi" ATTRS{device}=="0x0008" ATTRS{features}=="0110000000000000000000000000010000000000000000000000000000000000" ATTRS{status}=="0x00000007" ATTRS{vendor}=="0x1af4"

looking at parent device '/devices/pci0000:00/0000:00:03.0': KERNELS=="0000:00:03.0" SUBSYSTEMS=="pci" DRIVERS=="virtio-pci" ATTRS{irq}=="11" ATTRS{subsystem_vendor}=="0x1af4" ATTRS{broken_parity_status}=="0" ATTRS{class}=="0x000000" ATTRS{driver_override}=="(null)" ATTRS{consistent_dma_mask_bits}=="64" ATTRS{dma_mask_bits}=="64" ATTRS{local_cpus}=="3" ATTRS{device}=="0x1004" ATTRS{enable}=="1" ATTRS{msi_bus}=="" ATTRS{local_cpulist}=="0-1" ATTRS{vendor}=="0x1af4" ATTRS{subsystem_device}=="0x0008" ATTRS{numa_node}=="-1" ATTRS{d3cold_allowed}=="0"

looking at parent device '/devices/pci0000:00': KERNELS=="pci0000:00" SUBSYSTEMS=="" DRIVERS==""

# udevadm info -q all -a /dev/sdb

looking at device '/devices/pci0000:00/0000:00:04.0/virtio1/host1/target1:0:1/1:0:1:0/block/sdb': KERNEL=="sdb" SUBSYSTEM=="block" DRIVER=="" ATTR{ro}=="0" ATTR{size}=="786432000" ATTR{stat}==" 219 0 12776 101 16 0 4096 63 0 66 164" ATTR{range}=="16" ATTR{discard_alignment}=="0" ATTR{events}=="" ATTR{ext_range}=="256" ATTR{events_poll_msecs}=="-1" ATTR{alignment_offset}=="0" ATTR{badblocks}=="" ATTR{inflight}==" 0 0" ATTR{removable}=="0" ATTR{capability}=="50" ATTR{events_async}==""

looking at parent device '/devices/pci0000:00/0000:00:04.0/virtio1/host1/target1:0:1/1:0:1:0': KERNELS=="1:0:1:0" SUBSYSTEMS=="scsi" DRIVERS=="sd" ATTRS{rev}=="1 " ATTRS{type}=="0" ATTRS{scsi_level}=="7" ATTRS{model}=="EphemeralDisk " ATTRS{state}=="running" ATTRS{unpriv_sgio}=="0" ATTRS{queue_type}=="none" ATTRS{iodone_cnt}=="0x141" ATTRS{iorequest_cnt}=="0x141" ATTRS{device_busy}=="0" ATTRS{evt_capacity_change_reported}=="0" ATTRS{timeout}=="30" ATTRS{evt_media_change}=="0" ATTRS{ioerr_cnt}=="0x0" ATTRS{queue_depth}=="1024" ATTRS{vendor}=="Google " ATTRS{evt_soft_threshold_reached}=="0" ATTRS{device_blocked}=="0" ATTRS{evt_mode_parameter_change_reported}=="0" ATTRS{evt_lun_change_reported}=="0" ATTRS{evt_inquiry_change_reported}=="0" ATTRS{dh_state}=="detached" ATTRS{iocounterbits}=="32" ATTRS{inquiry}=="" ATTRS{vpd_pg80}=="" ATTRS{vpd_pg83}=="" ATTRS{eh_timeout}=="10"

looking at parent device '/devices/pci0000:00/0000:00:04.0/virtio1/host1/target1:0:1': KERNELS=="target1:0:1" SUBSYSTEMS=="scsi" DRIVERS==""

looking at parent device '/devices/pci0000:00/0000:00:04.0/virtio1/host1': KERNELS=="host1" SUBSYSTEMS=="scsi" DRIVERS==""

looking at parent device '/devices/pci0000:00/0000:00:04.0/virtio1': KERNELS=="virtio1" SUBSYSTEMS=="virtio" DRIVERS=="virtio_scsi" ATTRS{device}=="0x0008" ATTRS{features}=="0100000000000000000000000000010000000000000000000000000000000000" ATTRS{status}=="0x00000007" ATTRS{vendor}=="0x1af4"

looking at parent device '/devices/pci0000:00/0000:00:04.0': KERNELS=="0000:00:04.0" SUBSYSTEMS=="pci" DRIVERS=="virtio-pci" ATTRS{irq}=="10" ATTRS{subsystem_vendor}=="0x1af4" ATTRS{broken_parity_status}=="0" ATTRS{class}=="0x000000" ATTRS{driver_override}=="(null)" ATTRS{consistent_dma_mask_bits}=="64" ATTRS{dma_mask_bits}=="64" ATTRS{local_cpus}=="3" ATTRS{device}=="0x1004" ATTRS{enable}=="1" ATTRS{msi_bus}=="" ATTRS{local_cpulist}=="0-1" ATTRS{vendor}=="0x1af4" ATTRS{subsystem_device}=="0x0008" ATTRS{numa_node}=="-1" ATTRS{d3cold_allowed}=="0"

looking at parent device '/devices/pci0000:00': KERNELS=="pci0000:00" SUBSYSTEMS=="" DRIVERS==""