Configurable Error Injection

Overview

Configurable error injection allows injecting specific block layer status codes for sector ranges of a block device. Errors can be injected unconditionally, or with a given probability.

To use configurable error injection, CONFIG_BLK_ERROR_INJECTION must be enabled.

The only interface is the error_injection debugfs file, which is created for each registered gendisk. Writes to this file are used to create or delete rules and reads return a list of the current error injection sites.

Options

The following options specify the operations:

add	add a new rule
removeall	remove all existing rules

The following options specify the details of the rule for the add operation:

op=<string>	block layer operation this rule applies to. This uses the XYZ for each REQ_OP_XYZ operation, e.g. READ, WRITE or DISCARD. Mandatory.
status=<string>	Status to return. This uses XYZ for each BLK_STS_XYZ code, e.g. IOERR or MEDIUM. Mandatory.
start=<number>	First block layer sector the rule applies to. Optional, defaults to 0.
nr_sectors=<number>	Number of sectors this rule applies. Optional, defaults to the remainder of the device.
chance=<number>	Only return a failure with a likelihood of 1/chance. Optional, defaults to 1 (always).

Example

Return BLK_STS_IOERR for one in 10 reads of sector 0 of /dev/nvme0n1:

$ echo ‘add,op=READ,start=0,status=IOERR,chance=10’ > /sys/kernel/debug/block/nvme0n1/error_injection

Return BLK_STS_MEDIUM for every write to /dev/nvme0n1:

$ echo ‘add,op=WRITE,start=0,status=MEDIUM’ > /sys/kernel/debug/block/nvme0n1/error_injection

Remove all rules for /dev/nvme0n1:

$ echo ‘removeall’ > /sys/kernel/debug/block/nvme0n1/error_injection