Commit c732a852 authored by ZiyangZhang's avatar ZiyangZhang Committed by Jens Axboe
Browse files

ublk_drv: add START_USER_RECOVERY and END_USER_RECOVERY support 



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)chardev 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: default avatarZiyangZhang <ZiyangZhang@linux.alibaba.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220923153919.44078-7-ZiyangZhang@linux.alibaba.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent a0d41dc1

drivers/block/ublk_drv.c

+116 −0
Original line number Diff line number Diff line
@@ -1861,6 +1861,116 @@ 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);

	/* 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;

	init_completion(&ub->completion);

	ret = 0;

 out_unlock:

	mutex_unlock(&ub->mutex);

	ublk_put_device(ub);

	return ret;

}



static int ublk_ctrl_end_recovery(struct io_uring_cmd *cmd)

{

	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;

	int ublksrv_pid = (int)header->data[0];

	struct ublk_device *ub;

	int ret = -EINVAL;



	ub = ublk_get_device_from_id(header->dev_id);

	if (!ub)

		return ret;



	pr_devel("%s: Waiting for new ubq_daemons(nr: %d) are ready, dev id %d...\n",

			__func__, ub->dev_info.nr_hw_queues, header->dev_id);

	/* wait until new ubq_daemon sending all FETCH_REQ */

	wait_for_completion_interruptible(&ub->completion);

	pr_devel("%s: All new ubq_daemons(nr: %d) are ready, dev id %d\n",

			__func__, ub->dev_info.nr_hw_queues, header->dev_id);



	mutex_lock(&ub->mutex);

	if (!ublk_can_use_recovery(ub))

		goto out_unlock;



	if (ub->dev_info.state != UBLK_S_DEV_QUIESCED) {

		ret = -EBUSY;

		goto out_unlock;

	}

	ub->dev_info.ublksrv_pid = ublksrv_pid;

	pr_devel("%s: new ublksrv_pid %d, dev id %d\n",

			__func__, ublksrv_pid, header->dev_id);

	blk_mq_unquiesce_queue(ub->ub_disk->queue);

	pr_devel("%s: queue unquiesced, dev id %d.\n",

			__func__, header->dev_id);

	blk_mq_kick_requeue_list(ub->ub_disk->queue);

	ub->dev_info.state = UBLK_S_DEV_LIVE;

	schedule_delayed_work(&ub->monitor_work, UBLK_DAEMON_MONITOR_PERIOD);

	ret = 0;

 out_unlock:

	mutex_unlock(&ub->mutex);

	ublk_put_device(ub);

	return ret;

}



static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,

		unsigned int issue_flags)

{
@@ -1902,6 +2012,12 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd, 
	case UBLK_CMD_SET_PARAMS:

		ret = ublk_ctrl_set_params(cmd);

		break;

	case UBLK_CMD_START_USER_RECOVERY:

		ret = ublk_ctrl_start_recovery(cmd);

		break;

	case UBLK_CMD_END_USER_RECOVERY:

		ret = ublk_ctrl_end_recovery(cmd);

		break;

	default:

		break;

	}

include/uapi/linux/ublk_cmd.h

+2 −1
Original line number Diff line number Diff line
@@ -17,7 +17,8 @@ 
#define	UBLK_CMD_STOP_DEV	0x07

#define	UBLK_CMD_SET_PARAMS	0x08

#define	UBLK_CMD_GET_PARAMS	0x09



#define	UBLK_CMD_START_USER_RECOVERY	0x10

#define	UBLK_CMD_END_USER_RECOVERY	0x11

/*

 * IO commands, issued by ublk server, and handled by ublk driver.

 *