netdev - Re: [PATCH net-next v5 2/3] udp: implement memory accounting helpers

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Date:   Thu, 20 Oct 2016 14:10:34 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        James Morris <jmorris@...ei.org>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Alexander Duyck <aduyck@...antis.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Tom Herbert <tom@...bertland.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Edward Cree <ecree@...arflare.com>, linux-nfs@...r.kernel.org
Subject: Re: [PATCH net-next v5 2/3] udp: implement memory accounting helpers

On Thu, 2016-10-20 at 22:31 +0200, Paolo Abeni wrote:

> +
> +int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
> +{
> +	struct sk_buff_head *list = &sk->sk_receive_queue;
> +	int rmem, delta, amt, err = -ENOMEM;
> +	int size = skb->truesize;
> +
> +	/* try to avoid the costly atomic add/sub pair when the receive
> +	 * queue is full; always allow at least a packet
> +	 */
> +	rmem = atomic_read(&sk->sk_rmem_alloc);
> +	if (rmem && (rmem + size > sk->sk_rcvbuf))
> +		goto drop;
> +
> +	/* we drop only if the receive buf is full and the receive
> +	 * queue contains some other skb
> +	 */
> +	rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
> +	if ((rmem > sk->sk_rcvbuf) && (rmem > size))
> +		goto uncharge_drop;
> +
> +	skb_orphan(skb);

Minor point :

UDP should already have orphaned skbs ? (it uses skb_steal_sock())