netdev - Re: [PATCH net-next RFC v1 08/10] nvme-tcp: Deal with netdevice DOWN events

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Date:   Thu, 8 Oct 2020 15:47:37 -0700
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Boris Pismenny <borisp@...lanox.com>, kuba@...nel.org,
        davem@...emloft.net, saeedm@...dia.com, hch@....de, axboe@...com,
        kbusch@...nel.org, viro@...iv.linux.org.uk, edumazet@...gle.com
Cc:     Yoray Zack <yorayz@...lanox.com>,
        Ben Ben-Ishay <benishay@...lanox.com>,
        boris.pismenny@...il.com, linux-nvme@...ts.infradead.org,
        netdev@...r.kernel.org, Or Gerlitz <ogerlitz@...lanox.com>
Subject: Re: [PATCH net-next RFC v1 08/10] nvme-tcp: Deal with netdevice DOWN
 events



On 9/30/20 9:20 AM, Boris Pismenny wrote:
> From: Or Gerlitz <ogerlitz@...lanox.com>
> 
> For ddp setup/teardown and resync, the offloading logic
> uses HW resources at the NIC driver such as SQ and CQ.
> 
> These resources are destroyed when the netdevice does down
> and hence we must stop using them before the NIC driver
> destroyes them.
> 
> Use netdevice notifier for that matter -- offloaded connections
> are stopped before the stack continues to call the NIC driver
> close ndo.
> 
> We use the existing recovery flow which has the advantage
> of resuming the offload once the connection is re-set.
> 
> Since the recovery flow runs in a separate/dedicated WQ
> we need to wait in the notifier code for an ACK that all
> offloaded queues were stopped which means that the teardown
> queue offload ndo was called and the NIC doesn't have any
> resources related to that connection any more.
> 
> This also buys us proper handling for the UNREGISTER event
> b/c our offloading starts in the UP state, and down is always
> there between up to unregister.
> 
> Signed-off-by: Or Gerlitz <ogerlitz@...lanox.com>
> Signed-off-by: Boris Pismenny <borisp@...lanox.com>
> Signed-off-by: Ben Ben-Ishay <benishay@...lanox.com>
> Signed-off-by: Yoray Zack <yorayz@...lanox.com>
> ---
>   drivers/nvme/host/tcp.c | 39 +++++++++++++++++++++++++++++++++++++--
>   1 file changed, 37 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 9a620d1dacb4..7569b47f0414 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -144,6 +144,7 @@ struct nvme_tcp_ctrl {
>   
>   static LIST_HEAD(nvme_tcp_ctrl_list);
>   static DEFINE_MUTEX(nvme_tcp_ctrl_mutex);
> +static struct notifier_block nvme_tcp_netdevice_nb;
>   static struct workqueue_struct *nvme_tcp_wq;
>   static const struct blk_mq_ops nvme_tcp_mq_ops;
>   static const struct blk_mq_ops nvme_tcp_admin_mq_ops;
> @@ -412,8 +413,6 @@ int nvme_tcp_offload_limits(struct nvme_tcp_queue *queue,
>   		queue->ctrl->ctrl.max_segments = limits->max_ddp_sgl_len;
>   		queue->ctrl->ctrl.max_hw_sectors =
>   			limits->max_ddp_sgl_len << (ilog2(SZ_4K) - 9);
> -	} else {
> -		queue->ctrl->offloading_netdev = NULL;

Squash this change to the patch that introduced it.

>   	}
>   
>   	dev_put(netdev);
> @@ -1992,6 +1991,8 @@ static int nvme_tcp_alloc_admin_queue(struct nvme_ctrl *ctrl)
>   {
>   	int ret;
>   
> +	to_tcp_ctrl(ctrl)->offloading_netdev = NULL;
> +
>   	ret = nvme_tcp_alloc_queue(ctrl, 0, NVME_AQ_DEPTH);
>   	if (ret)
>   		return ret;
> @@ -2885,6 +2886,26 @@ static struct nvme_ctrl *nvme_tcp_create_ctrl(struct device *dev,
>   	return ERR_PTR(ret);
>   }
>   
> +static int nvme_tcp_netdev_event(struct notifier_block *this,
> +				 unsigned long event, void *ptr)
> +{
> +	struct net_device *ndev = netdev_notifier_info_to_dev(ptr);
> +	struct nvme_tcp_ctrl *ctrl;
> +
> +	switch (event) {
> +	case NETDEV_GOING_DOWN:
> +		mutex_lock(&nvme_tcp_ctrl_mutex);
> +		list_for_each_entry(ctrl, &nvme_tcp_ctrl_list, list) {
> +			if (ndev != ctrl->offloading_netdev)
> +				continue;
> +			nvme_tcp_error_recovery(&ctrl->ctrl);
> +		}
> +		mutex_unlock(&nvme_tcp_ctrl_mutex);
> +		flush_workqueue(nvme_reset_wq);

Worth a small comment that this we want the err_work to complete
here. So if someone changes workqueues he may see this.

> +	}
> +	return NOTIFY_DONE;
> +}
> +
>   static struct nvmf_transport_ops nvme_tcp_transport = {
>   	.name		= "tcp",
>   	.module		= THIS_MODULE,