Re: [PATCH v4 6/8] nvme-fc: fix controller reset hang during traffic

Himanshu Madhani
2021-08-02T19:39:17Z

On 8/2/21 6:26 AM, Daniel Wagner wrote:
> From: James Smart <jsmart2021@gmail.com>
>
> commit fe35ec58f0d3 ("block: update hctx map when use multiple maps")
> exposed an issue where we may hang trying to wait for queue freeze
> during I/O. We call blk_mq_update_nr_hw_queues which may attempt to freeze
> the queue. However we never started queue freeze when starting the
> reset, which means that we have inflight pending requests that entered the
> queue that we will not complete once the queue is quiesced.
>
> So start a freeze before we quiesce the queue, and unfreeze the queue
> after we successfully connected the I/O queues (the unfreeze is already
> present in the code). blk_mq_update_nr_hw_queues will be called only
> after we are sure that the queue was already frozen.
>
> This follows to how the pci driver handles resets.
>
> This patch added logic introduced in commit 9f98772ba307 "nvme-rdma: fix
> controller reset hang during traffic".
>
> Signed-off-by: James Smart <jsmart2021@gmail.com>
> CC: Sagi Grimberg <sagi@grimberg.me>
> [dwagner: call nvme_unfreeze() unconditionally in
> nvme_fc_recreate_io_queues() to match the nvme_start_freeze()]
> Tested-by: Daniel Wagner <dwagner@suse.de>
> Reviewed-by: Daniel Wagner <dwagner@suse.de>
> ---
> drivers/nvme/host/fc.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index 133b87db4f1d..b292af0fd655 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -2486,6 +2486,7 @@ __nvme_fc_abort_outstanding_ios(struct nvme_fc_ctrl *ctrl, bool start_queues)
> * (but with error status).
> */
> if (ctrl->ctrl.queue_count > 1) {
> + nvme_start_freeze(&ctrl->ctrl);
> nvme_stop_queues(&ctrl->ctrl);
> nvme_sync_io_queues(&ctrl->ctrl);
> blk_mq_tagset_busy_iter(&ctrl->tag_set,
> @@ -2966,8 +2967,8 @@ nvme_fc_recreate_io_queues(struct nvme_fc_ctrl *ctrl)
> return -ENODEV;
> }
> blk_mq_update_nr_hw_queues(&ctrl->tag_set, nr_io_queues);
> - nvme_unfreeze(&ctrl->ctrl);
> }
> + nvme_unfreeze(&ctrl->ctrl);
>
> ret = nvme_fc_create_hw_io_queues(ctrl, ctrl->ctrl.sqsize + 1);
> if (ret)
>

Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>

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Himanshu Madhani Oracle Linux Engineering