block: add documentation for io_timeout

Add documentation for /sys/block/<disk>/queue/io_timeout.

Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Weiping Zhang <zhangweiping@didiglobal.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index 7710d40..dfad742 100644 (file)
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -279,3 +279,12 @@ Description:
                size in 512B sectors of the zones of the device, with
                the eventual exception of the last zone of the device
                which may be smaller.
+
+What:          /sys/block/<disk>/queue/io_timeout
+Date:          November 2018
+Contact:       Weiping Zhang <zhangweiping@didiglobal.com>
+Description:
+               io_timeout is the request timeout in milliseconds. If a request
+               does not complete in this time then the block driver timeout
+               handler is invoked. That timeout handler can decide to retry
+               the request, to fail it or to start a device recovery strategy.

diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index 39e286d..83b457e 100644 (file)
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -67,6 +67,13 @@ If set to a value larger than 0, the kernel will put the process issuing
 IO to sleep for this amount of microseconds before entering classic
 polling.
 
+io_timeout (RW)
+---------------
+io_timeout is the request timeout in milliseconds. If a request does not
+complete in this time then the block driver timeout handler is invoked.
+That timeout handler can decide to retry the request, to fail it or to start
+a device recovery strategy.
+
 iostats (RW)
 -------------
 This file is used to control (on/off) the iostats accounting of the