On 11/1/24 8:34 AM, Ming Lei wrote: > On Fri, Nov 01, 2024 at 07:59:38AM -0600, Jens Axboe wrote: >> On 10/31/24 8:42 PM, Ming Lei wrote: >>> On Fri, Nov 01, 2024 at 10:12:25AM +0800, 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. >>> >>> Also IOSQE2_PERSONALITY doesn't have to be per-SQE, and it can be one >>> feature of IORING_FEAT_IOSQE2_PERSONALITY, that is why I thought it is >>> fine to take the 7th bit as SQE_GROUP now. >> >> Not sure I follow your thinking there, can you expand? > > It could be one io_uring setup flag, such as > IORING_SETUP_IOSQE2_PERSONALITY. > > If this flag is set, take __pad2 as sqe2_flags, otherwise use current > way, so it doesn't have to take bit7 of sqe_flags for this purpose. Would probably have to be a IORING_SETUP_IOSQE2_FLAGS or something in general. And while that could work, not a huge fan of that. I think we should retain that for when a v2 of the sqe is done, to coordinate which version to use. > Also in future, if uring_cmd needs personality, it still may reuse top > 16bit of uring_cmd_flags for that. Right, that's what I referred to in terms of uring_cmd just having its own way to set personality. -- Jens Axboe
