Re: [PATCH v2 1/3] fs/resctrl: Add helpers to check io_alloc support and enabled state

Reinette Chatre
2025-12-17T05:01:44Z

Hi Aaron,

On 12/15/25 3:02 PM, Aaron Tomlin wrote:
> This patch introduces two helpers to validate io_alloc support and
> whether it is enabled. This reduces code duplication, clarifies
> intent, and preserves existing semantics and messages.
>
> Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
> ---
> fs/resctrl/ctrlmondata.c | 74 +++++++++++++++++++++++++++++-----------
> 1 file changed, 54 insertions(+), 20 deletions(-)
>
> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
> index b2d178d3556e..d2f9a4f2d887 100644
> --- a/fs/resctrl/ctrlmondata.c
> +++ b/fs/resctrl/ctrlmondata.c
> @@ -758,6 +758,50 @@ u32 resctrl_io_alloc_closid(struct rdt_resource *r)
> return resctrl_arch_get_num_closid(r) - 1;
> }
>
> +/*
> + * resctrl_io_alloc_supported() - Establish if io_alloc is supported
> + *
> + * @s: resctrl resource schema.
> + *
> + * This function must be called under the cpu hotplug lock
> + * and rdtgroup mutex
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +static inline int resctrl_io_alloc_supported(struct resctrl_schema *s)
> +{
> + struct rdt_resource *r = s->res;
> +
> + if (!r->cache.io_alloc.io_alloc_capable) {
> + rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * resctrl_io_alloc_enabled() - Establish if io_alloc is enabled
> + *
> + * @s: resctrl resource schema
> + *
> + * This function must be called under the cpu hotplug lock
> + * and rdtgroup mutex
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +static inline int resctrl_io_alloc_enabled(struct resctrl_schema *s)
> +{
> + struct rdt_resource *r = s->res;
> +
> + if (!resctrl_arch_get_io_alloc_enabled(r)) {
> + rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
> size_t nbytes, loff_t off)
> {
> @@ -777,11 +821,9 @@ ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
>
> rdt_last_cmd_clear();
>
> - if (!r->cache.io_alloc_capable) {
> - rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
> - ret = -ENODEV;
> + ret = resctrl_io_alloc_supported(s);
> + if (ret)
> goto out_unlock;
> - }
>
> /* If the feature is already up to date, no action is needed. */
> if (resctrl_arch_get_io_alloc_enabled(r) == enable)
> @@ -839,17 +881,13 @@ int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
>
> rdt_last_cmd_clear();
>
> - if (!r->cache.io_alloc_capable) {
> - rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
> - ret = -ENODEV;
> + ret = resctrl_io_alloc_supported(s);
> + if (ret)
> goto out_unlock;
> - }
>
> - if (!resctrl_arch_get_io_alloc_enabled(r)) {
> - rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
> - ret = -EINVAL;
> + ret = resctrl_io_alloc_enabled(s);
> + if (ret)
> goto out_unlock;
> - }
>
> /*
> * When CDP is enabled, the CBMs of the highest CLOSID of CDP_CODE and
> @@ -928,17 +966,13 @@ ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of, char *buf,
> mutex_lock(&rdtgroup_mutex);
> rdt_last_cmd_clear();
>
> - if (!r->cache.io_alloc_capable) {
> - rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
> - ret = -ENODEV;
> + ret = resctrl_io_alloc_supported(s);
> + if (ret)
> goto out_unlock;
> - }
>
> - if (!resctrl_arch_get_io_alloc_enabled(r)) {
> - rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
> - ret = -EINVAL;
> + ret = resctrl_io_alloc_enabled(s);
> + if (ret)
> goto out_unlock;
> - }
>
> io_alloc_closid = resctrl_io_alloc_closid(r);
>

How does this patch benefit the goal of this submission, which is to set identical CBM on
all domains?

If this change benefited this submission I should find these new helpers used in later patches
but they are not. This seems to be an unrelated and unnecessary change mixed with this
submission. It does not fix a bug nor does it support this submission and thus just adds noise when
considering the new feature for inclusion. This patch can be dropped.

Reinette