On Tue, Sep 13, 2022 at 12:17:06PM +0800, ZiyangZhang wrote:
> START_USER_RECOVERY and END_USER_RECOVERY are two new control commands
> to support user recovery feature.
>
> After a crash, user should send START_USER_RECOVERY, it will:
> (1) check if (a)current ublk_device is UBLK_S_DEV_QUIESCED which was
> set by quiesce_work and (b)the file struct is released.
> (2) reinit all ubqs, including:
> (a) put the task_struct and reset ->ubq_daemon to NULL.
> (b) reset all ublk_io.
> (3) reset ub->mm to NULL.
>
> Then, user should start a new process and send FETCH_REQ on each
> ubq_daemon.
>
> Finally, user should send END_USER_RECOVERY, it will:
> (1) wait for all new ubq_daemons getting ready.
> (2) update ublksrv_pid
> (3) unquiesce the request queue and expect incoming ublk_queue_rq()
> (4) convert ub's state to UBLK_S_DEV_LIVE
>
> Note: we can handle STOP_DEV between START_USER_RECOVERY and
> END_USER_RECOVERY. This is helpful to users who cannot start new process
> after sending START_USER_RECOVERY ctrl-cmd.
>
> Signed-off-by: ZiyangZhang <ZiyangZhang@xxxxxxxxxxxxxxxxx>
> ---
> drivers/block/ublk_drv.c | 116 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 116 insertions(+)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 4409a130d0b6..3a3af80ee938 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1961,6 +1961,116 @@ static int ublk_ctrl_set_params(struct io_uring_cmd *cmd)
> return ret;
> }
>
> +static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
> +{
> + int i;
> +
> + WARN_ON_ONCE(!(ubq->ubq_daemon && ubq_daemon_is_dying(ubq)));
> + /* All old ioucmds have to be completed */
> + WARN_ON_ONCE(ubq->nr_io_ready);
> + pr_devel("%s: prepare for recovering qid %d\n", __func__, ubq->q_id);
> + /* old daemon is PF_EXITING, put it now */
> + put_task_struct(ubq->ubq_daemon);
> + /* We have to reset it to NULL, otherwise ub won't accept new FETCH_REQ */
> + ubq->ubq_daemon = NULL;
> +
> + for (i = 0; i < ubq->q_depth; i++) {
> + struct ublk_io *io = &ubq->ios[i];
> +
> + /* forget everything now and be ready for new FETCH_REQ */
> + io->flags = 0;
> + io->cmd = NULL;
> + io->addr = 0;
> + }
> +}
> +
> +static int ublk_ctrl_start_recovery(struct io_uring_cmd *cmd)
> +{
> + struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
> + struct ublk_device *ub;
> + int ret = -EINVAL;
> + int i;
> +
> + ub = ublk_get_device_from_id(header->dev_id);
> + if (!ub)
> + return ret;
> +
> + mutex_lock(&ub->mutex);
> + if (!ublk_can_use_recovery(ub))
> + goto out_unlock;
> + /*
> + * START_RECOVERY is only allowd after:
> + *
> + * (1) UB_STATE_OPEN is not set, which means the dying process is exited
> + * and related io_uring ctx is freed so file struct of /dev/ublkcX is
> + * released.
> + *
> + * (2) UBLK_S_DEV_QUIESCED is set, which means the quiesce_work:
> + * (a)has quiesced request queue
> + * (b)has requeued every inflight rqs whose io_flags is ACTIVE
> + * (c)has requeued/aborted every inflight rqs whose io_flags is NOT ACTIVE
> + * (d)has completed/camceled all ioucmds owned by ther dying process
> + */
> + if (test_bit(UB_STATE_OPEN, &ub->state) ||
> + ub->dev_info.state != UBLK_S_DEV_QUIESCED) {
> + ret = -EBUSY;
> + goto out_unlock;
> + }
> + pr_devel("%s: start recovery for dev id %d.\n", __func__, header->dev_id);
> + for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
> + ublk_queue_reinit(ub, ublk_get_queue(ub, i));
> + /* set to NULL, otherwise new ubq_daemon cannot mmap the io_cmd_buf */
> + ub->mm = NULL;
> + ub->nr_queues_ready = 0;
I am wondering why you don't move the above(queue reinit, clearing ub->mm)
into ublk_ch_release(), and looks it is more clean to clear this stuff
there. Meantime I guess one control command might be enough for user
recovery.
Thanks,
Ming
