On Fri, Nov 01, 2024 at 08:42:42AM -0600, Jens Axboe wrote: > 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. Fair enough. Now there are 16bits for new features, which may put v2 off long enough. > > > 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. Then this approach is safe to go, imo. Thanks, Ming
