Re: [PATCH net v2] xdp, net: fix for construct skb by xdp inside xsk zc rx

On 28/06/2021 12.47, Maciej Fijalkowski wrote:

+static __always_inline struct sk_buff *
+xdp_construct_skb(struct xdp_buff *xdp, struct napi_struct *napi)
+{

I don't like the generic name "xdp_construct_skb".

What about calling it "xdp_copy_construct_skb", because below is 
memcpy'ing the data.

Functions that use this call free (or recycle) the memory backing the 
packet, after calling this function.

(I'm open to other naming suggestions)

+	unsigned int metasize;
+	unsigned int datasize;
+	unsigned int headroom;
+	struct sk_buff *skb;
+	unsigned int len;
+
+	/* this include metasize */
+	datasize = xdp->data_end  - xdp->data_meta;
+	metasize = xdp->data      - xdp->data_meta;
+	headroom = xdp->data_meta - xdp->data_hard_start;
+	len      = xdp->data_end  - xdp->data_hard_start;
+
+	/* allocate a skb to store the frags */
+	skb = __napi_alloc_skb(napi, len, GFP_ATOMIC | __GFP_NOWARN);
+	if (unlikely(!skb))
+		return NULL;
+
+	skb_reserve(skb, headroom);
+	memcpy(__skb_put(skb, datasize), xdp->data_meta, datasize);
+	if (metasize) {
+		__skb_pull(skb, metasize);
+		skb_metadata_set(skb, metasize);
+	}
+
+	return skb;
+}