> diff --git a/Documentation/admin-guide/cgroup-v2.rst
> b/Documentation/admin-guide/cgroup-v2.rst
> index 86a2a0099178e..5786d86eceeae 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
[ ... ]
> @@ -2120,6 +2120,18 @@ IO Interface Files
> parameters are written to, "ctrl" become "user" and the
> automatic changes are disabled.
>
> + When CONFIG_BLK_CGROUP_IOCOST_BPF is enabled, "model" also accepts
> + the name of a registered iocost_model_ops BPF struct_ops model:
> + "model=<name>" binds the model to the device and the model fully
> + replaces the builtin linear pricing, for every operation including
> + flushes; "model=linear" (or "ctrl=auto/user") restores the builtin
> + model. Writing an unknown name fails with ENOENT and nothing is
> + applied. Unregistering a model removes its name so it can no
> + longer be selected; devices already bound keep using it, and keep
> + receiving cgroup lifecycle notifications, until switched back to
> + the builtin model. See
> + include/linux/blk-iocost.h for the model interface.
> +
Does this section need to document what io.cost.model reads back with
a BPF model bound?
Looking at ioc_cost_model_prfill() in block/blk-iocost.c, when a BPF
model is bound, the file prints:
seq_printf(sf, "%s ctrl=%s model=%s\n",
dname, model ? "bpf" : ioc->user_cost_model ? "user" : "auto",
model ? model->name : "linear");
So with a model bound, io.cost.model reads back "ctrl=bpf model=<name>".
The nested-key table nine lines above this paragraph lists the possible
values:
===== ================================
ctrl "auto" or "user"
model The cost model in use - "linear"
===== ================================
This table doesn't include "bpf" as a ctrl value or "<name>" as a model
value. The new paragraph also doesn't mention that "ctrl=bpf" is accepted
on write - ioc_cost_model_write() special-cases it so saved configurations
can be restored:
} else if (!strcmp(buf, "bpf")) {
/* readback value; keep the bound model */
continue;
}
Should the table be updated to include the "bpf" ctrl value and the
"<name>" model value, so the section documents what the kernel actually
prints?
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/35070283830
