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

Signed-off-by: Weiping Zhang <redacted>
---
 Documentation/ABI/testing/sysfs-block | 10 ++++++++++
 Documentation/block/queue-sysfs.txt   |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index dea212db9df3..f254a374710a 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block

@@ -271,3 +271,13 @@ Description:
 		size of 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 a request’s timeouts at block layer in
+		milliseconds. When the underlying driver starts processing
+		a request, the generic block layer will start a timer, if
+		this request cannot be completed in io_timeout milliseconds,
+		a timeout event will occur.

diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index 2c1e67058fd3..f0c9bbce73fd 100644
--- 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 amont of microseconds before entering classic
 polling.
 
+io_timeout (RW)
+---------------
+This is a request’s timeouts at block layer in milliseconds. When the
+underlying driver starts processing a request, the generic block layer
+will start a timer, if this request cannot be completed in io_timeout
+milliseconds, a timeout event will occur.
+
 iostats (RW)
 -------------
 This file is used to control (on/off) the iostats accounting of the

-- 
2.14.1