linux-kernel - Re: [PATCH rdma-next 2/2] RDMA/core: Add a netevent notifier to cma

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Message-ID: <20220511000411.GA1164300@nvidia.com>
Date:   Tue, 10 May 2022 21:04:11 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Patrisious Haddad <phaddad@...dia.com>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        Mark Zhang <markzhang@...dia.com>
Subject: Re: [PATCH rdma-next 2/2] RDMA/core: Add a netevent notifier to cma

On Mon, Apr 04, 2022 at 03:27:27PM +0300, Leon Romanovsky wrote:

> @@ -5054,10 +5061,95 @@ static int cma_netdev_callback(struct notifier_block *self, unsigned long event,
>  	return ret;
>  }
>  
> +static void cma_netevent_work_handler(struct work_struct *_work)
> +{
> +	struct cma_netevent_work *network =
> +		container_of(_work, struct cma_netevent_work, work);
> +	struct rdma_cm_event event = {};
> +
> +	mutex_lock(&network->id_priv->handler_mutex);
> +
> +	if (READ_ONCE(network->id_priv->state) == RDMA_CM_DESTROYING ||
> +	    READ_ONCE(network->id_priv->state) == RDMA_CM_DEVICE_REMOVAL)
> +		goto out_unlock;
> +
> +	event.event = RDMA_CM_EVENT_UNREACHABLE;
> +	event.status = -ETIMEDOUT;
> +
> +	if (cma_cm_event_handler(network->id_priv, &event)) {
> +		__acquire(&network->id_priv->handler_mutex);

??

> +		network->id_priv->cm_id.ib = NULL;
> +		cma_id_put(network->id_priv);
> +		destroy_id_handler_unlock(network->id_priv);
> +		kfree(network);
> +		return;
> +	}
> +
> +out_unlock:
> +	mutex_unlock(&network->id_priv->handler_mutex);
> +	cma_id_put(network->id_priv);
> +	kfree(network);
> +}
> +
> +static int cma_netevent_callback(struct notifier_block *self,
> +				 unsigned long event, void *ctx)
> +{
> +	struct id_table_entry *ips_node = NULL;
> +	struct rdma_id_private *current_id;
> +	struct cma_netevent_work *network;
> +	struct neighbour *neigh = ctx;
> +	unsigned long flags;
> +
> +	if (event != NETEVENT_NEIGH_UPDATE)
> +		return NOTIFY_DONE;
> +
> +	spin_lock_irqsave(&id_table_lock, flags);
> +	if (neigh->tbl->family == AF_INET6) {
> +		struct sockaddr_in6 neigh_sock_6;
> +
> +		neigh_sock_6.sin6_family = AF_INET6;
> +		neigh_sock_6.sin6_addr = *(struct in6_addr *)neigh->primary_key;
> +		ips_node = node_from_ndev_ip(&id_table, neigh->dev->ifindex,
> +					     (struct sockaddr *)&neigh_sock_6);
> +	} else if (neigh->tbl->family == AF_INET) {
> +		struct sockaddr_in neigh_sock_4;
> +
> +		neigh_sock_4.sin_family = AF_INET;
> +		neigh_sock_4.sin_addr.s_addr = *(__be32 *)(neigh->primary_key);
> +		ips_node = node_from_ndev_ip(&id_table, neigh->dev->ifindex,
> +					     (struct sockaddr *)&neigh_sock_4);
> +	} else
> +		goto out;
> +
> +	if (!ips_node)
> +		goto out;
> +
> +	list_for_each_entry(current_id, &ips_node->id_list, id_list_entry) {
> +		if (!memcmp(current_id->id.route.addr.dev_addr.dst_dev_addr,
> +			   neigh->ha, ETH_ALEN))
> +			continue;
> +		network = kzalloc(sizeof(*network), GFP_ATOMIC);
> +		if (!network)
> +			goto out;
> +
> +		INIT_WORK(&network->work, cma_netevent_work_handler);
> +		network->id_priv = current_id;
> +		cma_id_get(current_id);
> +		queue_work(cma_netevent_wq, &network->work);

This is pretty ugly that we need to do atomic allocations for every
matching id.

It would be better to add the work directly to the rdma_cm_id and just
waste that memory.

> +	cma_netevent_wq = alloc_ordered_workqueue("rdma_cm_netevent", 0);
> +	if (!cma_netevent_wq) {
> +		ret = -ENOMEM;
> +		goto err_netevent_wq;
> +	}

Why do we need another WQ? Why does it need to be ordered?

Jason