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. Also in future, if uring_cmd needs personality, it still may reuse top 16bit of uring_cmd_flags for that. Thanks, Ming
