How to Set “dev_loss_tmo” Value Persistently Using Udev Rule?

1. Check the attributes of the FC remote port(s) using the below command:

# udevadm info --attribute-walk --path=/sys/class/fc_remote_ports/rport-x:y-z

2. Then create udev rules that match all viable rports by matching the ‘role’ mentioned in the attributes returned in the above command. For example, create /etc/udev/rules.d/99-tmo.rules and include the below contents.

ACTION!="add|change", GOTO="tmo_end"
KERNELS=="rport-?*", SUBSYSTEM=="XXXX", ATTR{roles}=="XXXX", ATTR{dev_loss_tmo}="xx"
LABEL="tmo_end"

In the example, attributes returned from the 1st command’s output where,

SUBSYSTEM="fc_remote_ports"
roles="FCP Target"
dev_loss_tmo=30

So the rule to increase the dev_loss_tmo to 700000 will be as;

ACTION!="add|change", GOTO="tmo_end"
KERNELS=="rport-?*", SUBSYSTEM=="fc_remote_ports", ATTR{roles}=="FCP Target", ATTR{dev_loss_tmo}="700000"
LABEL="tmo_end"

3. Then reload the udev rules:

# udevadm control --reload

4. Trigger the rules for the subsystem:

# udevadm trigger --subsystem-match="XXXX"

Note: If the attribute fast_io_fail_tmo returns 0 or off, enable it as well for the dev_loss_tmo attribute to take effect.

For example:

ACTION!="add|change", GOTO="tmo_end"
KERNELS=="rport-?*", SUBSYSTEM=="fc_remote_ports", ATTR{roles}=="FCP Target", ATTR{dev_loss_tmo}="700000", ATTR{fast_io_fail_tmo}="5"
LABEL="tmo_end"