On Tue, 2024-08-20 at 18:53 -0700, Haitao Huang wrote:
> +/**
> + * misc_cg_set_ops() - register resource specific operations.
> + * @type: Type of the misc res.
> + * @ops: Operations for the given type.
> + *
> + * The callbacks in @ops will not be invoked if the capacity of @type is 0.
> + *
> + * Context: Any context.
> + * Return:
> + * * %0 - Successfully registered the operations.
> + * * %-EINVAL - If @type is invalid, or the operations missing any required callbacks.
> + */
> +int misc_cg_set_ops(enum misc_res_type type, const struct misc_res_ops *ops)
> +{
> + if (!valid_type(type))
> + return -EINVAL;
> +
> + if (!ops)
> + return -EINVAL;
> +
> + if (!ops->alloc) {
> + pr_err("%s: alloc missing\n", __func__);
> + return -EINVAL;
> + }
> +
> + if (!ops->free) {
> + pr_err("%s: free missing\n", __func__);
> + return -EINVAL;
> + }
> +
> + misc_res_ops[type] = ops;
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(misc_cg_set_ops);
As mentioned in another reply, the export isn't mandatory for SGX cgroup
support due to SGX driver cannot be a module.
But I understand the intention is to treat this in a similar way to
misc_cg_set_capacity() etc which are currently exported.
I have no hard opinion whether to export this one. But if we export this, I
don't quite like the fact that it doesn't accept the NULL ops to allow the
caller to unwind.
But I'll leave to cgroup maintainers.
> +
> /**
> * misc_cg_cancel_charge() - Cancel the charge from the misc cgroup.
> * @type: Misc res type in misc cg to cancel the charge from.
> @@ -439,6 +477,36 @@ static struct cftype misc_cg_files[] = {
> {}
> };
>
> +static inline void _misc_cg_res_free(struct misc_cg *cg, enum misc_res_type last)
> +{
> + enum misc_res_type i;
> +
> + for (i = 0; i <= last; i++)
> + if (misc_res_ops[i] && READ_ONCE(misc_res_capacity[i]))
> + misc_res_ops[i]->free(cg);
> +}
> +
> +static inline int _misc_cg_res_alloc(struct misc_cg *cg)
> +{
> + enum misc_res_type i;
> + int ret;
> +
> + for (i = 0; i < MISC_CG_RES_TYPES; i++) {
> + WRITE_ONCE(cg->res[i].max, MAX_NUM);
> + atomic64_set(&cg->res[i].usage, 0);
> +
> + if (misc_res_ops[i] && READ_ONCE(misc_res_capacity[i])) {
> + ret = misc_res_ops[i]->alloc(cg);
> + if (ret) {
> + _misc_cg_res_free(cg, i);
> + return ret;
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
I don't fully understand why kernel uses READ_ONCE()/WRITE_ONCE() to access
misc_res_capacity[i] and others like 'cg->res[i].max', but it looks weird they
are not used when accessing misc_res_ops[i]?
