On Mon, Apr 14, 2025 at 07:25:45PM +0800, Ming Lei wrote:
> Now ublk deals with ublk_nosrv_dev_should_queue_io() by keeping request
> queue as quiesced. This way is fragile because queue quiesce crosses syscalls
> or process contexts.
>
> Switch to rely on ubq->canceling for dealing with ublk_nosrv_dev_should_queue_io(),
> because it has been used for this purpose during io_uring context exiting, and it
> can be reused before recovering too.
>
> Meantime we have to move reset of ubq->canceling from ublk_ctrl_end_recovery() to
> ublk_ctrl_end_recovery(), when IO handling can be recovered completely.
First one here should be ublk_ctrl_start_recovery or ublk_queue_reinit
>
> Then blk_mq_quiesce_queue() and blk_mq_unquiesce_queue() are always used
> in same context.
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> drivers/block/ublk_drv.c | 31 +++++++++++++++++--------------
> 1 file changed, 17 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 7e2c4084c243..e0213222e3cf 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1734,13 +1734,19 @@ static void ublk_wait_tagset_rqs_idle(struct ublk_device *ub)
>
> static void __ublk_quiesce_dev(struct ublk_device *ub)
> {
> + int i;
> +
> pr_devel("%s: quiesce ub: dev_id %d state %s\n",
> __func__, ub->dev_info.dev_id,
> ub->dev_info.state == UBLK_S_DEV_LIVE ?
> "LIVE" : "QUIESCED");
> blk_mq_quiesce_queue(ub->ub_disk->queue);
> + /* mark every queue as canceling */
> + for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
> + ublk_get_queue(ub, i)->canceling = true;
> ublk_wait_tagset_rqs_idle(ub);
> ub->dev_info.state = UBLK_S_DEV_QUIESCED;
> + blk_mq_unquiesce_queue(ub->ub_disk->queue);
So the queue is not actually quiesced when we are in UBLK_S_DEV_QUIESCED
anymore, and we rely on __ublk_abort_rq to requeue I/O submitted in this
QUIESCED state. This requeued I/O will immediately resubmit, right?
Isn't this a waste of CPU?
> }
>
> static void ublk_force_abort_dev(struct ublk_device *ub)
> @@ -2950,7 +2956,6 @@ static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
> /* We have to reset it to NULL, otherwise ub won't accept new FETCH_REQ */
> ubq->ubq_daemon = NULL;
> ubq->timeout = false;
> - ubq->canceling = false;
>
> for (i = 0; i < ubq->q_depth; i++) {
> struct ublk_io *io = &ubq->ios[i];
> @@ -3037,20 +3042,18 @@ static int ublk_ctrl_end_recovery(struct ublk_device *ub,
> pr_devel("%s: new ublksrv_pid %d, dev id %d\n",
> __func__, ublksrv_pid, header->dev_id);
>
> - if (ublk_nosrv_dev_should_queue_io(ub)) {
> - ub->dev_info.state = UBLK_S_DEV_LIVE;
> - 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);
> - } else {
> - blk_mq_quiesce_queue(ub->ub_disk->queue);
> - ub->dev_info.state = UBLK_S_DEV_LIVE;
> - for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
> - ublk_get_queue(ub, i)->fail_io = false;
> - }
> - blk_mq_unquiesce_queue(ub->ub_disk->queue);
> + blk_mq_quiesce_queue(ub->ub_disk->queue);
> + ub->dev_info.state = UBLK_S_DEV_LIVE;
> + for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
> + struct ublk_queue *ubq = ublk_get_queue(ub, i);
> +
> + ubq->canceling = false;
> + ubq->fail_io = false;
> }
> + 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);
>
> ret = 0;
> out_unlock:
> --
> 2.47.0
>
