block: add fault injection mechanism for faking request timeouts

Only works for the generic request timer handling. Allows one to
sporadically ignore request completions, thus exercising the timeout
handling.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

lib/Kconfig.debug

@@ -683,10 +683,21 @@ config FAIL_PAGE_ALLOC
 
 config FAIL_MAKE_REQUEST
 	bool "Fault-injection capability for disk IO"
-	depends on FAULT_INJECTION
+	depends on FAULT_INJECTION && BLOCK
 	help
 	  Provide fault-injection capability for disk IO.
 
+config FAIL_IO_TIMEOUT
+	bool "Faul-injection capability for faking disk interrupts"
+	depends on FAULT_INJECTION && BLOCK
+	help
+	  Provide fault-injection capability on end IO handling. This
+	  will make the block layer "forget" an interrupt as configured,
+	  thus exercising the error handling.
+
+	  Only works with drivers that use the generic timeout handling,
+	  for others it wont do anything.
+
 config FAULT_INJECTION_DEBUG_FS
 	bool "Debugfs entries for fault-injection capabilities"
 	depends on FAULT_INJECTION && SYSFS && DEBUG_FS