.. SPDX-License-Identifier: GPL-2.0 ============================Configurable Error Injection============================ Overview-------- Configurable error injection allows injecting specific block layer status codesfor sector ranges of a block device.  Errors can be injected unconditionally, orwith 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 foreach registered gendisk.  Writes to this file are used to create or delete rulesand reads return a list of the current error injection sites. Options------- The following options specify the operations: ===================	=======================================================add			add a new ruleremoveall		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