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Mon, 01 Dec 2025 20:44:45 -0500 X-MC-Unique: jfA1qgB0Me2eygrw6PRYnw-1 X-Mimecast-MFC-AGG-ID: jfA1qgB0Me2eygrw6PRYnw_1764639884 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ABE0F180045C; Tue, 2 Dec 2025 01:44:43 +0000 (UTC) Received: from fedora (unknown [10.72.116.20]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BD24219560A7; Tue, 2 Dec 2025 01:44:38 +0000 (UTC) Date: Tue, 2 Dec 2025 09:44:33 +0800 From: Ming Lei To: Caleb Sander Mateos Cc: Jens Axboe , linux-block@vger.kernel.org, Uday Shankar , Stefani Seibold , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH V4 16/27] ublk: add new feature UBLK_F_BATCH_IO Message-ID: References: <20251121015851.3672073-1-ming.lei@redhat.com> <20251121015851.3672073-17-ming.lei@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On Mon, Dec 01, 2025 at 01:16:04PM -0800, Caleb Sander Mateos wrote: > On Thu, Nov 20, 2025 at 6:00 PM Ming Lei wrote: > > > > 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_GET_DATA isn't supported in batch io yet, but it may be > > UBLK_U_IO_NEED_GET_DATA? Yeah. > > > enabled in future via its batch pair. > > > > Signed-off-by: Ming Lei > > --- > > drivers/block/ublk_drv.c | 58 ++++++++++++++++++++++++++++++++--- > > include/uapi/linux/ublk_cmd.h | 16 ++++++++++ > > 2 files changed, 69 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c > > index 849199771f86..90cd1863bc83 100644 > > --- a/drivers/block/ublk_drv.c > > +++ b/drivers/block/ublk_drv.c > > @@ -74,7 +74,8 @@ > > | UBLK_F_AUTO_BUF_REG \ > > | UBLK_F_QUIESCE \ > > | UBLK_F_PER_IO_DAEMON \ > > - | UBLK_F_BUF_REG_OFF_DAEMON) > > + | UBLK_F_BUF_REG_OFF_DAEMON \ > > + | UBLK_F_BATCH_IO) > > > > #define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \ > > | UBLK_F_USER_RECOVERY_REISSUE \ > > @@ -320,12 +321,12 @@ static void ublk_batch_dispatch(struct ublk_queue *ubq, > > > > static inline bool ublk_dev_support_batch_io(const struct ublk_device *ub) > > { > > - return false; > > + return ub->dev_info.flags & UBLK_F_BATCH_IO; > > } > > > > static inline bool ublk_support_batch_io(const struct ublk_queue *ubq) > > { > > - return false; > > + return ubq->flags & UBLK_F_BATCH_IO; > > } > > > > static inline void ublk_io_lock(struct ublk_io *io) > > @@ -3450,6 +3451,41 @@ static int ublk_validate_batch_fetch_cmd(struct ublk_batch_io_data *data, > > return 0; > > } > > > > +static int ublk_handle_non_batch_cmd(struct io_uring_cmd *cmd, > > + unsigned int issue_flags) > > +{ > > + const struct ublksrv_io_cmd *ub_cmd = io_uring_sqe_cmd(cmd->sqe); > > + struct ublk_device *ub = cmd->file->private_data; > > + unsigned tag = READ_ONCE(ub_cmd->tag); > > + unsigned q_id = READ_ONCE(ub_cmd->q_id); > > + unsigned index = READ_ONCE(ub_cmd->addr); > > + struct ublk_queue *ubq; > > + struct ublk_io *io; > > + int ret = -EINVAL; > > I think it would be clearer to just return -EINVAL instead of adding > this variable, but up to you > > > + > > + if (!ub) > > + return ret; > > How is this case possible? Will remove the check. > > > + > > + if (q_id >= ub->dev_info.nr_hw_queues) > > + return ret; > > + > > + ubq = ublk_get_queue(ub, q_id); > > + if (tag >= ubq->q_depth) > > Can avoid the likely cache miss here by using ub->dev_info.queue_depth > instead, analogous to ublk_ch_uring_cmd_local() OK. > > > + return ret; > > + > > + io = &ubq->ios[tag]; > > + > > + switch (cmd->cmd_op) { > > + case UBLK_U_IO_REGISTER_IO_BUF: > > + return ublk_register_io_buf(cmd, ub, q_id, tag, io, index, > > + issue_flags); > > + case UBLK_U_IO_UNREGISTER_IO_BUF: > > + return ublk_unregister_io_buf(cmd, ub, index, issue_flags); > > + default: > > + return -EOPNOTSUPP; > > + } > > +} > > + > > static int ublk_ch_batch_io_uring_cmd(struct io_uring_cmd *cmd, > > unsigned int issue_flags) > > { > > @@ -3497,7 +3533,8 @@ static int ublk_ch_batch_io_uring_cmd(struct io_uring_cmd *cmd, > > ret = ublk_handle_batch_fetch_cmd(&data); > > break; > > default: > > - ret = -EOPNOTSUPP; > > + ret = ublk_handle_non_batch_cmd(cmd, issue_flags); > > We should probably skip the if (data.header.q_id >= > ub->dev_info.nr_hw_queues) check for a non-batch command? It is true only for UBLK_IO_UNREGISTER_IO_BUF. > > > + break; > > } > > out: > > return ret; > > @@ -4163,9 +4200,13 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header) > > > > ub->dev_info.flags |= UBLK_F_CMD_IOCTL_ENCODE | > > UBLK_F_URING_CMD_COMP_IN_TASK | > > - UBLK_F_PER_IO_DAEMON | > > + (ublk_dev_support_batch_io(ub) ? 0 : UBLK_F_PER_IO_DAEMON) | > > Seems redundant with the logic below to clear UBLK_F_PER_IO_DAEMON if > (ublk_dev_support_batch_io(ub))? Good catch. > > > UBLK_F_BUF_REG_OFF_DAEMON; > > > > + /* So far, UBLK_F_PER_IO_DAEMON won't be exposed for BATCH_IO */ > > + if (ublk_dev_support_batch_io(ub)) > > + ub->dev_info.flags &= ~UBLK_F_PER_IO_DAEMON; > > + > > /* GET_DATA isn't needed any more with USER_COPY or ZERO COPY */ > > if (ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY | > > UBLK_F_AUTO_BUF_REG)) > > @@ -4518,6 +4559,13 @@ static int ublk_wait_for_idle_io(struct ublk_device *ub, > > unsigned int elapsed = 0; > > int ret; > > > > + /* > > + * For UBLK_F_BATCH_IO ublk server can get notified with existing > > + * or new fetch command, so needn't wait any more > > + */ > > + if (ublk_dev_support_batch_io(ub)) > > + return 0; > > + > > while (elapsed < timeout_ms && !signal_pending(current)) { > > unsigned int queues_cancelable = 0; > > int i; > > diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h > > index cd894c1d188e..5e8b1211b7f4 100644 > > --- a/include/uapi/linux/ublk_cmd.h > > +++ b/include/uapi/linux/ublk_cmd.h > > @@ -335,6 +335,22 @@ > > */ > > #define UBLK_F_BUF_REG_OFF_DAEMON (1ULL << 14) > > > > + > > +/* > > + * Support the following commands for delivering & committing io command > > + * in batch. > > + * > > + * - UBLK_U_IO_PREP_IO_CMDS > > + * - UBLK_U_IO_COMMIT_IO_CMDS > > + * - UBLK_U_IO_FETCH_IO_CMDS > > + * - UBLK_U_IO_REGISTER_IO_BUF > > + * - UBLK_U_IO_UNREGISTER_IO_BUF > > Seems like it might make sense to provided batched versions of > UBLK_U_IO_REGISTER_IO_BUF and UBLK_U_IO_UNREGISTER_IO_BUF. That could > be done in the future, I guess, but it might simplify > ublk_ch_batch_io_uring_cmd() to only have to handle struct > ublk_batch_io. Agree, and it can be added in future. Thanks, Ming