Re: [PATCH v2 2/2] io_uring/timeout: immediate timeout arg

[Jens Axboe <axboe@kernel.dk>]

On 2/27/26 12:08 PM, Pavel Begunkov wrote:
> On 2/27/26 14:08, Stefan Metzmacher wrote:
>> Hi Pavel,
>>
>>>       if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
>>>           return -EINVAL;
>>> @@ -460,10 +461,20 @@ int io_timeout_remove_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>               return -EINVAL;
>>>           if (tr->flags & IORING_LINK_TIMEOUT_UPDATE)
>>>               tr->ltimeout = true;
>>> -        if (tr->flags & ~(IORING_TIMEOUT_UPDATE_MASK|IORING_TIMEOUT_ABS))
>>> +        if (tr->flags & ~(IORING_TIMEOUT_UPDATE_MASK |
>>> +                  IORING_TIMEOUT_ABS |
>>> +                  IORING_TIMEOUT_IMMEDIATE_ARG))
>>>               return -EINVAL;
>>> -        if (get_timespec64(&tr->ts, u64_to_user_ptr(READ_ONCE(sqe->addr2))))
>>> +
>>> +        arg = READ_ONCE(sqe->addr2);
>>> +        if (tr->flags & IORING_TIMEOUT_IMMEDIATE_ARG) {
>>> +            if (tr->flags & IORING_TIMEOUT_ABS)
>>> +                return -EINVAL;
>>> +            tr->ts = ns_to_timespec64(arg);
>>
>> I'm wondering if there is enough free space in a small sqe to hold a full timespec?
>> So that there is no restriction for IORING_TIMEOUT_ABS...
> 
> Well, u64 gives ~500 years in ns, it should be fine to just
> allow the abs mode. We just need to make sure to zero check
> the unused fields in case it'd need to be extended.

I don't think it's about length of it - if you can avoid the div by
doing ns_to_timespec64(), that might be very useful? Would make
userspace simpler too potentially, and basically make the immediate mode
_exactly_ the same as the non-immediate mode, it just delivers the
__kernel_timespec in a different way.

-- 
Jens Axboe