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diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 3b29005aa981..1521c7e554f5 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1435,6 +1435,100 @@ IO Interface Files
8:16 rbytes=1459200 wbytes=314773504 rios=192 wios=353 dbytes=0 dios=0
8:0 rbytes=90430464 wbytes=299008000 rios=8950 wios=1252 dbytes=50331648 dios=3021
+ io.cost.qos
+ A read-write nested-keyed file with exists only on the root
+ cgroup.
+
+ This file configures the Quality of Service of the IO cost
+ model based controller (CONFIG_BLK_CGROUP_IOCOST) which
+ currently implements "io.weight" proportional control. Lines
+ are keyed by $MAJ:$MIN device numbers and not ordered. The
+ line for a given device is populated on the first write for
+ the device on "io.cost.qos" or "io.cost.model". The following
+ nested keys are defined.
+
+ ====== =====================================
+ enable Weight-based control enable
+ ctrl "auto" or "user"
+ rpct Read latency percentile [0, 100]
+ rlat Read latency threshold
+ wpct Write latency percentile [0, 100]
+ wlat Write latency threshold
+ min Minimum scaling percentage [1, 10000]
+ max Maximum scaling percentage [1, 10000]
+ ====== =====================================
+
+ The controller is disabled by default and can be enabled by
+ setting "enable" to 1. "rpct" and "wpct" parameters default
+ to zero and the controller uses internal device saturation
+ state to adjust the overall IO rate between "min" and "max".
+
+ When a better control quality is needed, latency QoS
+ parameters can be configured. For example::
+
+ 8:16 enable=1 ctrl=auto rpct=95.00 rlat=75000 wpct=95.00 wlat=150000 min=50.00 max=150.0
+
+ shows that on sdb, the controller is enabled, will consider
+ the device saturated if the 95th percentile of read completion
+ latencies is above 75ms or write 150ms, and adjust the overall
+ IO issue rate between 50% and 150% accordingly.
+
+ The lower the saturation point, the better the latency QoS at
+ the cost of aggregate bandwidth. The narrower the allowed
+ adjustment range between "min" and "max", the more conformant
+ to the cost model the IO behavior. Note that the IO issue
+ base rate may be far off from 100% and setting "min" and "max"
+ blindly can lead to a significant loss of device capacity or
+ control quality. "min" and "max" are useful for regulating
+ devices which show wide temporary behavior changes - e.g. a
+ ssd which accepts writes at the line speed for a while and
+ then completely stalls for multiple seconds.
+
+ When "ctrl" is "auto", the parameters are controlled by the
+ kernel and may change automatically. Setting "ctrl" to "user"
+ or setting any of the percentile and latency parameters puts
+ it into "user" mode and disables the automatic changes. The
+ automatic mode can be restored by setting "ctrl" to "auto".
+
+ io.cost.model
+ A read-write nested-keyed file with exists only on the root
+ cgroup.
+
+ This file configures the cost model of the IO cost model based
+ controller (CONFIG_BLK_CGROUP_IOCOST) which currently
+ implements "io.weight" proportional control. Lines are keyed
+ by $MAJ:$MIN device numbers and not ordered. The line for a
+ given device is populated on the first write for the device on
+ "io.cost.qos" or "io.cost.model". The following nested keys
+ are defined.
+
+ ===== ================================
+ ctrl "auto" or "user"
+ model The cost model in use - "linear"
+ ===== ================================
+
+ When "ctrl" is "auto", the kernel may change all parameters
+ dynamically. When "ctrl" is set to "user" or any other
+ parameters are written to, "ctrl" become "user" and the
+ automatic changes are disabled.
+
+ When "model" is "linear", the following model parameters are
+ defined.
+
+ ============= ========================================
+ [r|w]bps The maximum sequential IO throughput
+ [r|w]seqiops The maximum 4k sequential IOs per second
+ [r|w]randiops The maximum 4k random IOs per second
+ ============= ========================================
+
+ From the above, the builtin linear model determines the base
+ costs of a sequential and random IO and the cost coefficient
+ for the IO size. While simple, this model can cover most
+ common device classes acceptably.
+
+ The IO cost model isn't expected to be accurate in absolute
+ sense and is scaled to the device behavior dynamically.
+
io.weight
A read-write flat-keyed file which exists on non-root cgroups.
The default is "default 100".