ublk: kill queuing request by task_work_add

task_work_add() is used from early ublk development stage for handling
request in batch. However, since commit 7d4a93176e01 ("ublk_drv: don't
forward io commands in reserve order"), we can get similar batch
processing with io_uring_cmd_complete_in_task(), and similar performance
data is observed between task_work_add() and
io_uring_cmd_complete_in_task().

Meantime we can kill one fast code path, which is actually seldom used
given it is common to build ublk driver as module.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230519065030.351216-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index c7ed5d69e9eee2545c0f4458ce6f4a1847060cde..b00c5c210c7f3ec52455af54feaa3727731e7126 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -62,7 +62,6 @@
 
 struct ublk_rq_data {
        struct llist_node node;
-       struct callback_head work;
 };
 
 struct ublk_uring_cmd_pdu {
@@ -290,14 +289,6 @@ static int ublk_apply_params(struct ublk_device *ub)
        return 0;
 }
 
-static inline bool ublk_can_use_task_work(const struct ublk_queue *ubq)
-{
-       if (IS_BUILTIN(CONFIG_BLK_DEV_UBLK) &&
-                       !(ubq->flags & UBLK_F_URING_CMD_COMP_IN_TASK))
-               return true;
-       return false;
-}
-
 static inline bool ublk_need_get_data(const struct ublk_queue *ubq)
 {
        return ubq->flags & UBLK_F_NEED_GET_DATA;
@@ -852,17 +843,6 @@ static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd, unsigned issue_flags)
        ublk_forward_io_cmds(ubq, issue_flags);
 }
 
-static void ublk_rq_task_work_fn(struct callback_head *work)
-{
-       struct ublk_rq_data *data = container_of(work,
-                       struct ublk_rq_data, work);
-       struct request *req = blk_mq_rq_from_pdu(data);
-       struct ublk_queue *ubq = req->mq_hctx->driver_data;
-       unsigned issue_flags = IO_URING_F_UNLOCKED;
-
-       ublk_forward_io_cmds(ubq, issue_flags);
-}
-
 static void ublk_queue_cmd(struct ublk_queue *ubq, struct request *rq)
 {
        struct ublk_rq_data *data = blk_mq_rq_to_pdu(rq);
@@ -886,10 +866,6 @@ static void ublk_queue_cmd(struct ublk_queue *ubq, struct request *rq)
         */
        if (unlikely(io->flags & UBLK_IO_FLAG_ABORTED)) {
                ublk_abort_io_cmds(ubq);
-       } else if (ublk_can_use_task_work(ubq)) {
-               if (task_work_add(ubq->ubq_daemon, &data->work,
-                                       TWA_SIGNAL_NO_IPI))
-                       ublk_abort_io_cmds(ubq);
        } else {
                struct io_uring_cmd *cmd = io->cmd;
                struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
@@ -961,19 +937,9 @@ static int ublk_init_hctx(struct blk_mq_hw_ctx *hctx, void *driver_data,
        return 0;
 }
 
-static int ublk_init_rq(struct blk_mq_tag_set *set, struct request *req,
-               unsigned int hctx_idx, unsigned int numa_node)
-{
-       struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
-
-       init_task_work(&data->work, ublk_rq_task_work_fn);
-       return 0;
-}
-
 static const struct blk_mq_ops ublk_mq_ops = {
        .queue_rq       = ublk_queue_rq,
        .init_hctx      = ublk_init_hctx,
-       .init_request   = ublk_init_rq,
        .timeout        = ublk_timeout,
 };
 
@@ -1813,10 +1779,8 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
         */
        ub->dev_info.flags &= UBLK_F_ALL;
 
-       if (!IS_BUILTIN(CONFIG_BLK_DEV_UBLK))
-               ub->dev_info.flags |= UBLK_F_URING_CMD_COMP_IN_TASK;
-
-       ub->dev_info.flags |= UBLK_F_CMD_IOCTL_ENCODE;
+       ub->dev_info.flags |= UBLK_F_CMD_IOCTL_ENCODE |
+               UBLK_F_URING_CMD_COMP_IN_TASK;
 
        /* We are not ready to support zero copy */
        ub->dev_info.flags &= ~UBLK_F_SUPPORT_ZERO_COPY;