Suopport to lease block IO buffer for userpace to run io_uring operations(FS, network IO), then ublk zero copy can be supported. userspace code: git clone https://github.com/ublk-org/ublksrv.git -b uring_group And both loop and nbd zero copy(io_uring send and send zc) are covered. Performance improvement is quite obvious in big block size test, such as 'loop --buffered_io' perf is doubled in 64KB block test("loop/007 vs loop/009"). Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- drivers/block/ublk_drv.c | 160 ++++++++++++++++++++++++++++++++-- include/uapi/linux/ublk_cmd.h | 11 ++- 2 files changed, 161 insertions(+), 10 deletions(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 6ba2c1dd1d87..5803c6418d1e 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -51,6 +51,8 @@ /* private ioctl command mirror */ #define UBLK_CMD_DEL_DEV_ASYNC _IOC_NR(UBLK_U_CMD_DEL_DEV_ASYNC) +#define UBLK_IO_PROVIDE_IO_BUF _IOC_NR(UBLK_U_IO_PROVIDE_IO_BUF) + /* All UBLK_F_* have to be included into UBLK_F_ALL */ #define UBLK_F_ALL (UBLK_F_SUPPORT_ZERO_COPY \ | UBLK_F_URING_CMD_COMP_IN_TASK \ @@ -71,6 +73,9 @@ struct ublk_rq_data { struct llist_node node; struct kref ref; + + bool allocated_bvec; + struct io_mapped_buf buf[0]; }; struct ublk_uring_cmd_pdu { @@ -189,11 +194,15 @@ struct ublk_params_header { __u32 types; }; +static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub, + struct ublk_queue *ubq, int tag, size_t offset); static bool ublk_abort_requests(struct ublk_device *ub, struct ublk_queue *ubq); static inline unsigned int ublk_req_build_flags(struct request *req); static inline struct ublksrv_io_desc *ublk_get_iod(struct ublk_queue *ubq, int tag); +static void ublk_io_buf_giveback_cb(const struct io_mapped_buf *buf); + static inline bool ublk_dev_is_user_copy(const struct ublk_device *ub) { return ub->dev_info.flags & UBLK_F_USER_COPY; @@ -588,6 +597,11 @@ static inline bool ublk_need_req_ref(const struct ublk_queue *ubq) return ublk_support_user_copy(ubq); } +static inline bool ublk_support_zc(const struct ublk_queue *ubq) +{ + return ubq->flags & UBLK_F_SUPPORT_ZERO_COPY; +} + static inline void ublk_init_req_ref(const struct ublk_queue *ubq, struct request *req) { @@ -851,6 +865,72 @@ static size_t ublk_copy_user_pages(const struct request *req, return done; } +/* + * The built command buffer is immutable, so it is fine to feed it to + * concurrent io_uring provide buf commands + */ +static int ublk_init_zero_copy_buffer(struct request *req) +{ + struct ublk_rq_data *data = blk_mq_rq_to_pdu(req); + struct io_mapped_buf *imu = data->buf; + struct req_iterator rq_iter; + unsigned int nr_bvecs = 0; + struct bio_vec *bvec; + unsigned int offset; + struct bio_vec bv; + + if (!ublk_rq_has_data(req)) + goto exit; + + rq_for_each_bvec(bv, req, rq_iter) + nr_bvecs++; + + if (!nr_bvecs) + goto exit; + + if (req->bio != req->biotail) { + int idx = 0; + + bvec = kvmalloc_array(nr_bvecs, sizeof(struct bio_vec), + GFP_NOIO); + if (!bvec) + return -ENOMEM; + + offset = 0; + rq_for_each_bvec(bv, req, rq_iter) + bvec[idx++] = bv; + data->allocated_bvec = true; + } else { + struct bio *bio = req->bio; + + offset = bio->bi_iter.bi_bvec_done; + bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); + } + imu->kbuf = 1; + imu->pbvec = bvec; + imu->nr_bvecs = nr_bvecs; + imu->offset = offset; + imu->len = blk_rq_bytes(req); + imu->dir = req_op(req) == REQ_OP_READ ? ITER_DEST : ITER_SOURCE; + imu->kbuf_ack = ublk_io_buf_giveback_cb; + + return 0; +exit: + imu->pbvec = NULL; + return 0; +} + +static void ublk_deinit_zero_copy_buffer(struct request *req) +{ + struct ublk_rq_data *data = blk_mq_rq_to_pdu(req); + struct io_mapped_buf *imu = data->buf; + + if (data->allocated_bvec) { + kvfree(imu->pbvec); + data->allocated_bvec = false; + } +} + static inline bool ublk_need_map_req(const struct request *req) { return ublk_rq_has_data(req) && req_op(req) == REQ_OP_WRITE; @@ -862,13 +942,25 @@ static inline bool ublk_need_unmap_req(const struct request *req) (req_op(req) == REQ_OP_READ || req_op(req) == REQ_OP_DRV_IN); } -static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req, +static int ublk_map_io(const struct ublk_queue *ubq, struct request *req, struct ublk_io *io) { const unsigned int rq_bytes = blk_rq_bytes(req); - if (ublk_support_user_copy(ubq)) + if (ublk_support_user_copy(ubq)) { + if (ublk_support_zc(ubq)) { + int ret = ublk_init_zero_copy_buffer(req); + + /* + * The only failure is -ENOMEM for allocating providing + * buffer command, return zero so that we can requeue + * this req. + */ + if (unlikely(ret)) + return 0; + } return rq_bytes; + } /* * no zero copy, we delay copy WRITE request data into ublksrv @@ -886,13 +978,16 @@ static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req, } static int ublk_unmap_io(const struct ublk_queue *ubq, - const struct request *req, + struct request *req, struct ublk_io *io) { const unsigned int rq_bytes = blk_rq_bytes(req); - if (ublk_support_user_copy(ubq)) + if (ublk_support_user_copy(ubq)) { + if (ublk_support_zc(ubq)) + ublk_deinit_zero_copy_buffer(req); return rq_bytes; + } if (ublk_need_unmap_req(req)) { struct iov_iter iter; @@ -1038,6 +1133,7 @@ static inline void __ublk_complete_rq(struct request *req) return; exit: + ublk_deinit_zero_copy_buffer(req); blk_mq_end_request(req, res); } @@ -1680,6 +1776,45 @@ static inline void ublk_prep_cancel(struct io_uring_cmd *cmd, io_uring_cmd_mark_cancelable(cmd, issue_flags); } +static void ublk_io_buf_giveback_cb(const struct io_mapped_buf *buf) +{ + struct ublk_rq_data *data = container_of(buf, struct ublk_rq_data, buf[0]); + struct request *req = blk_mq_rq_from_pdu(data); + struct ublk_queue *ubq = req->mq_hctx->driver_data; + + ublk_put_req_ref(ubq, req); +} + +static int ublk_provide_io_buf(struct io_uring_cmd *cmd, + struct ublk_queue *ubq, int tag) +{ + struct ublk_device *ub = cmd->file->private_data; + struct ublk_rq_data *data; + struct request *req; + + if (!ub) + return -EPERM; + + req = __ublk_check_and_get_req(ub, ubq, tag, 0); + if (!req) + return -EINVAL; + + pr_devel("%s: qid %d tag %u request bytes %u\n", + __func__, tag, ubq->q_id, blk_rq_bytes(req)); + + data = blk_mq_rq_to_pdu(req); + + /* + * io_uring guarantees that the callback will be called after + * the provided buffer is consumed, and it is automatic removal + * before this uring command is freed. + * + * This request won't be completed unless the callback is called, + * so ublk module won't be unloaded too. + */ + return io_uring_cmd_lease_kbuf(cmd, data->buf); +} + static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags, const struct ublksrv_io_cmd *ub_cmd) @@ -1731,6 +1866,10 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd, ret = -EINVAL; switch (_IOC_NR(cmd_op)) { + case UBLK_IO_PROVIDE_IO_BUF: + if (unlikely(!ublk_support_zc(ubq))) + goto out; + return ublk_provide_io_buf(cmd, ubq, tag); case UBLK_IO_FETCH_REQ: /* UBLK_IO_FETCH_REQ is only allowed before queue is setup */ if (ublk_queue_ready(ubq)) { @@ -2149,11 +2288,14 @@ static void ublk_align_max_io_size(struct ublk_device *ub) static int ublk_add_tag_set(struct ublk_device *ub) { + int zc = !!(ub->dev_info.flags & UBLK_F_SUPPORT_ZERO_COPY); + struct ublk_rq_data *data; + ub->tag_set.ops = &ublk_mq_ops; ub->tag_set.nr_hw_queues = ub->dev_info.nr_hw_queues; ub->tag_set.queue_depth = ub->dev_info.queue_depth; ub->tag_set.numa_node = NUMA_NO_NODE; - ub->tag_set.cmd_size = sizeof(struct ublk_rq_data); + ub->tag_set.cmd_size = struct_size(data, buf, zc); ub->tag_set.flags = BLK_MQ_F_SHOULD_MERGE; ub->tag_set.driver_data = ub; return blk_mq_alloc_tag_set(&ub->tag_set); @@ -2458,8 +2600,12 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd) goto out_free_dev_number; } - /* We are not ready to support zero copy */ - ub->dev_info.flags &= ~UBLK_F_SUPPORT_ZERO_COPY; + /* zero copy depends on user copy */ + if ((ub->dev_info.flags & UBLK_F_SUPPORT_ZERO_COPY) && + !ublk_dev_is_user_copy(ub)) { + ret = -EINVAL; + goto out_free_dev_number; + } ub->dev_info.nr_hw_queues = min_t(unsigned int, ub->dev_info.nr_hw_queues, nr_cpu_ids); diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index 12873639ea96..04d73b349709 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -94,6 +94,8 @@ _IOWR('u', UBLK_IO_COMMIT_AND_FETCH_REQ, struct ublksrv_io_cmd) #define UBLK_U_IO_NEED_GET_DATA \ _IOWR('u', UBLK_IO_NEED_GET_DATA, struct ublksrv_io_cmd) +#define UBLK_U_IO_PROVIDE_IO_BUF \ + _IOWR('u', 0x23, struct ublksrv_io_cmd) /* only ABORT means that no re-fetch */ #define UBLK_IO_RES_OK 0 @@ -127,9 +129,12 @@ #define UBLKSRV_IO_BUF_TOTAL_SIZE (1ULL << UBLKSRV_IO_BUF_TOTAL_BITS) /* - * zero copy requires 4k block size, and can remap ublk driver's io - * request into ublksrv's vm space - */ + * io_uring provide kbuf command based zero copy + * + * Not available for UBLK_F_UNPRIVILEGED_DEV, because we rely on ublk + * server to fill up request buffer for READ IO, and ublk server can't + * be trusted in case of UBLK_F_UNPRIVILEGED_DEV. +*/ #define UBLK_F_SUPPORT_ZERO_COPY (1ULL << 0) /* -- 2.47.0
