blk-wbt: allow reset of default latency through sysfs
Allow a write of '-1' to reset the default latency target for
a given device. This removes knowledge of the different default
settings for rotational vs non-rotational from user space.
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index 14235e7..5164215 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -188,7 +188,9 @@
If the device is registered for writeback throttling, then this file shows
the target minimum read latency. If this latency is exceeded in a given
window of time (see wb_window_usec), then the writeback throttling will start
-scaling back writes.
+scaling back writes. Writing a value of '0' to this file disables the
+feature. Writing a value of '-1' to this file resets the value to the
+default setting.
Jens Axboe <jens.axboe@oracle.com>, February 2009