linux-kernel - Re: [PATCH V2 1/1] ubd: add io_uring based userspace block driver

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Date:   Tue, 17 May 2022 18:00:57 +0800
From:   Ziyang Zhang <ZiyangZhang@...ux.alibaba.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Harris James R <james.r.harris@...el.com>,
        io-uring@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH V2 1/1] ubd: add io_uring based userspace block driver

On 2022/5/17 13:53, Ming Lei wrote:

> +
> +static void ubd_cancel_queue(struct ubd_queue *ubq)
> +{
> +	int i;
> +
> +	for (i = 0; i < ubq->q_depth; i++) {
> +		struct ubd_io *io = &ubq->ios[i];
> +
> +		if (io->flags & UBD_IO_FLAG_ACTIVE) {
> +			io->flags &= ~UBD_IO_FLAG_ACTIVE;
> +			io_uring_cmd_done(io->cmd, UBD_IO_RES_ABORT, 0);
> +		}
> +	}
> +}

Hi Ming,

When ubdsrv sends STOP_DEV and all active IOs in ubd_drv are done(UBD_IO_RES_ABORT),
there may be still some IOs handled by ubdsrv(UBD_IO_FLAG_ACTIVE not set).
When these IOs complete and return to ubd_drv, how to handle them?
I find that UBD_IO_FETCH_REQ are still set,
so will these IOs be issued to ubdsrv again or canceled?
(I see ubd_drv fails IOs when the daemon is dying 
but maybe here the daemon is still alive)



> +
> +/* Cancel all pending commands, must be called after del_gendisk() returns */
> +static void ubd_cancel_dev(struct ubd_device *ub)
> +{
> +	int i;
> +
> +	for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
> +		ubd_cancel_queue(ubd_get_queue(ub, i));
> +}
> +
> +static void ubd_stop_dev(struct ubd_device *ub)
> +{
> +	mutex_lock(&ub->mutex);
> +	if (!disk_live(ub->ub_disk))
> +		goto unlock;
> +
> +	del_gendisk(ub->ub_disk);
> +	ub->dev_info.state = UBD_S_DEV_DEAD;
> +	ub->dev_info.ubdsrv_pid = -1;
> +	ubd_cancel_dev(ub);
> + unlock:
> +	mutex_unlock(&ub->mutex);
> +	cancel_delayed_work_sync(&ub->monitor_work);
> +}
> +
> +static int ubd_ctrl_stop_dev(struct ubd_device *ub)
> +{
> +	ubd_stop_dev(ub);
> +	return 0;
> +}
> +