Christoph Hellwig [off-list ref] 于2018年12月5日周三 下午10:40写道：

Can you please also send a patch to not show this attribute for
drivers without a timeout handler?  Thanks!

Do you means checking q->mq_ops->timeout is NULL or not ?

static void blk_mq_rq_timed_out(struct request *req, bool reserved)
{
        req->rq_flags |= RQF_TIMED_OUT;
If it's NULL, only re-start a timer for this request in blk_add_timer.
Is there some defect ? if show this attribute and the driver doesn't
support timeout handler ？

        if (req->q->mq_ops->timeout) {
                enum blk_eh_timer_return ret;

                ret = req->q->mq_ops->timeout(req, reserved);
                if (ret == BLK_EH_DONE)
                        return;
                WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
        }

        blk_add_timer(req);
}

On Wed, Dec 05, 2018 at 10:17:06PM +0800, Weiping Zhang wrote:

quoted

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

---end quoted text---