Re: [PATCH RFC] io_uring: extend io_uring_sqe flags bits

[Jens Axboe <axboe@kernel.dk>]

On 10/31/24 8:12 PM, Ming Lei wrote:
> On Thu, Oct 31, 2024 at 03:22:18PM -0600, Jens Axboe wrote:
>> In hindsight everything is clearer, but it probably should've been known
>> that 8 bits of ->flags would run out sooner than later. Rather than
>> gobble up the last bit for a random use case, add a bit that controls
>> whether or not ->personality is used as a flags2 argument. If that is
>> the case, then there's a new IOSQE2_PERSONALITY flag that tells io_uring
>> which personality field to read.
>>
>> While this isn't the prettiest, it does allow extending with 15 extra
>> flags, and retains being able to use personality with any kind of
>> command. The exception is uring cmd, where personality2 will overlap
>> with the space set aside for SQE128. If they really need that, then that
> 
> The space is the 1st `short` for uring_cmd, instead of SQE128 only.
> 
> Also it is overlapped with ->optval and ->addr3, so just wondering why not
> use ->__pad2?
> 
> Another ways is to use __pad2 for sqe2_flags for non-uring_cmd, and for
> uring_cmd, use its top 16 as sqe2_flags, this way does work, but it is
> just a bit ugly to use.

Agree, __pad2 is the better place, we don't want it overlapping with
add3/optval.

-- 
Jens Axboe