mm: document /sys/class/bdi/<bdi>/min_bytes knob

This documents the new /sys/class/bdi/<bdi>/min_bytes knob.

[akpm@linux-foundation.org: fix htmldocs warnings]
Link: https://lkml.kernel.org/r/20221119005215.3052436-15-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi
index 580f723..a9a2f58 100644 (file)
--- a/Documentation/ABI/testing/sysfs-class-bdi
+++ b/Documentation/ABI/testing/sysfs-class-bdi
@@ -57,6 +57,21 @@ Description:
 
        (read-write)
 
+What:          /sys/class/bdi/<bdi>/min_bytes
+Date:          October 2022
+Contact:       Stefan Roesch <shr@devkernel.io>
+Description:
+       Under normal circumstances each device is given a part of the
+       total write-back cache that relates to its current average
+       writeout speed in relation to the other devices.
+
+       The 'min_bytes' parameter allows assigning a minimum
+       percentage of the write-back cache to a particular device
+       expressed in bytes.
+       For example, this is useful for providing a minimum QoS.
+
+       (read-write)
+
 What:          /sys/class/bdi/<bdi>/max_bytes
 Date:          October 2022
 Contact:       Stefan Roesch <shr@devkernel.io>