Ammar Faizi <ammarfaizi2@xxxxxxxxxxx> writes:
> On Wed, Feb 01, 2023 at 02:22:53PM -0800, Stefan Roesch wrote:
>> +static int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
>> +{
>> +#ifdef CONFIG_NET_RX_BUSY_POLL
>> + const struct io_uring_napi curr = {
>> + .busy_poll_to = ctx->napi_busy_poll_to,
>> + };
>> +
>> + if (arg) {
>> + if (copy_to_user(arg, &curr, sizeof(curr)))
>> + return -EFAULT;
>> + }
>> +
>> + WRITE_ONCE(ctx->napi_busy_poll_to, 0);
>> + return 0;
>> +#else
>> + return -EINVAL;
>> +#endif
>> +}
>
> Just to follow the common pattern when a feature is not enabled the
> return value is -EOPNOTSUPP instead of -EINVAL. What do you think?
>
Sounds good, I'll return -EOPNOTSUPP when CONFIG_NET_RX_BUSY_POLL is not
enabled. I'll make the change for the register and the unregister
function.
>> + case IORING_UNREGISTER_NAPI:
>> + ret = -EINVAL;
>> + if (!arg)
>> + break;
>> + ret = io_unregister_napi(ctx, arg);
>> + break;
>
> This needs to be corrected. If the @arg var is NULL, you return -EINVAL.
> So io_unregister_napi() will always have @arg != NULL. This @arg check
> should go, allow the user to pass a NULL pointer to it.
>
> Our previous agreement on this API is to allow the user to pass a NULL
> pointer in case the user doesn't care about the old value.
>
> Also, having a liburing test case that verifies this behavior would be
> excellent.
>
I'll remove the check for the arg parameter. In addition I will output
the busy poll timeout and the prefer busy poll setting in the client
example program if one of the settings has been enabled.
