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e2723e6ce6
Add new feature UBLK_F_BATCH_IO which replaces the following two per-io commands: - UBLK_U_IO_FETCH_REQ - UBLK_U_IO_COMMIT_AND_FETCH_REQ with three per-queue batch io uring_cmd: - UBLK_U_IO_PREP_IO_CMDS - UBLK_U_IO_COMMIT_IO_CMDS - UBLK_U_IO_FETCH_IO_CMDS Then ublk can deliver batch io commands to ublk server in single multishort uring_cmd, also allows to prepare & commit multiple commands in batch style via single uring_cmd, communication cost is reduced a lot. This feature also doesn't limit task context any more for all supported commands, so any allowed uring_cmd can be issued in any task context. ublk server implementation becomes much easier. Meantime load balance becomes much easier to support with this feature. The command `UBLK_U_IO_FETCH_IO_CMDS` can be issued from multiple task contexts, so each task can adjust this command's buffer length or number of inflight commands for controlling how much load is handled by current task. Later, priority parameter will be added to command `UBLK_U_IO_FETCH_IO_CMDS` for improving load balance support. UBLK_U_IO_NEED_GET_DATA isn't supported in batch io yet, but it may be enabled in future via its batch pair. Reviewed-by: Caleb Sander Mateos <csander@purestorage.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>