netdev - Re: [PATCH V2 net-next 06/14] net/tls: Add generic NIC offload infrastructure

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Date:   Wed, 21 Mar 2018 14:10:25 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Dave Watson <davejwatson@...com>,
        Boris Pismenny <borisp@...lanox.com>,
        Ilya Lesokhin <ilyal@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>
Subject: Re: [PATCH V2 net-next 06/14] net/tls: Add generic NIC offload
 infrastructure



On 03/21/2018 02:01 PM, Saeed Mahameed wrote:
> From: Ilya Lesokhin <ilyal@...lanox.com>
> 
> This patch adds a generic infrastructure to offload TLS crypto to a

...

> +
> +static inline int tls_push_record(struct sock *sk,
> +				  struct tls_context *ctx,
> +				  struct tls_offload_context *offload_ctx,
> +				  struct tls_record_info *record,
> +				  struct page_frag *pfrag,
> +				  int flags,
> +				  unsigned char record_type)
> +{
> +	skb_frag_t *frag;
> +	struct tcp_sock *tp = tcp_sk(sk);
> +	struct page_frag fallback_frag;
> +	struct page_frag  *tag_pfrag = pfrag;
> +	int i;
> +
> +	/* fill prepand */
> +	frag = &record->frags[0];
> +	tls_fill_prepend(ctx,
> +			 skb_frag_address(frag),
> +			 record->len - ctx->prepend_size,
> +			 record_type);
> +
> +	if (unlikely(!skb_page_frag_refill(ctx->tag_size, pfrag, GFP_KERNEL))) {
> +		/* HW doesn't care about the data in the tag
> +		 * so in case pfrag has no room
> +		 * for a tag and we can't allocate a new pfrag
> +		 * just use the page in the first frag
> +		 * rather then write a complicated fall back code.
> +		 */
> +		tag_pfrag = &fallback_frag;
> +		tag_pfrag->page = skb_frag_page(frag);
> +		tag_pfrag->offset = 0;
> +	}
> +

If HW does not care, why even trying to call skb_page_frag_refill() ?

If you remove it, then we remove one seldom used path and might uncover bugs

This part looks very suspect to me, to be honest.