[PATCH] nvme-core: fix deadlock when delete ctrl due to reconnect fail

[Chao Leng]

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On 2020/7/27 16:01, Chao Leng wrote:
> A deadlock happens when test link blink for nvme over roce. If time out
> in reconneting process, nvme_rdma_timeout->nvme_rdma_teardown_io_queues
> will quiesce the io queues, and then the ctrl will be deleted after
> reconnect times exceed max_reconnects. If run fdisk from the time
> when the queue is quiesced to the time when the ctrl is deleted,
> delete ctrl will deadlock, the process: nvme_do_delete_ctrl->
> nvme_remove_namespaces->nvme_ns_remove->blk_cleanup_queue->
> blk_freeze_queue->blk_mq_freeze_queue_wait, blk_mq_freeze_queue_wait
> will wait until q_usage_counter of queue become 0, but the queue is
> quiesced, can not clean any request.
> 
> Solution: nvme_rdma_timeout should call nvme_start_queues after
> call nvme_rdma_teardown_io_queues. further more, we need start queues
> regardless of whether the remove flag is set, after cancel requests
> in nvme_rdma_teardown_io_queues.
> 
> Signed-off-by: Chao Leng <lengchao at huawei.com>
> ---
>   drivers/nvme/host/rdma.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
> index f8f856dc0c67..b381e2cde50a 100644
> --- a/drivers/nvme/host/rdma.c
> +++ b/drivers/nvme/host/rdma.c
> @@ -989,8 +989,7 @@ static void nvme_rdma_teardown_io_queues(struct nvme_rdma_ctrl *ctrl,
>   				nvme_cancel_request, &ctrl->ctrl);
>   			blk_mq_tagset_wait_completed_request(ctrl->ctrl.tagset);
>   		}
> -		if (remove)
> -			nvme_start_queues(&ctrl->ctrl);
> +		nvme_start_queues(&ctrl->ctrl);
>   		nvme_rdma_destroy_io_queues(ctrl, remove);
>   	}
>   }
> @@ -1128,7 +1127,6 @@ static void nvme_rdma_error_recovery_work(struct work_struct *work)
>   
>   	nvme_stop_keep_alive(&ctrl->ctrl);
>   	nvme_rdma_teardown_io_queues(ctrl, false);
> -	nvme_start_queues(&ctrl->ctrl);
>   	nvme_rdma_teardown_admin_queue(ctrl, false);
>   	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
>   
>