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Commit f36c3747 authored by Ian Campbell's avatar Ian Campbell Committed by David S. Miller
Browse files

xen/netfront: handle compound page fragments on transmit 



An SKB paged fragment can consist of a compound page with order > 0.
However the netchannel protocol deals only in PAGE_SIZE frames.

Handle this in xennet_make_frags by iterating over the frames which
make up the page.

This is the netfront equivalent to 6a8ed462 for netback.

Signed-off-by: default avatarIan Campbell <ian.campbell@citrix.com>
Cc: netdev@vger.kernel.org
Cc: xen-devel@lists.xen.org
Cc: Eric Dumazet <edumazet@google.com>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: ANNIE LI <annie.li@oracle.com>
Cc: Sander Eikelenboom <linux@eikelenboom.it>
Cc: Stefan Bader <stefan.bader@canonical.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f30a9443

drivers/net/xen-netfront.c

+77 −21
Original line number Diff line number Diff line
@@ -452,29 +452,85 @@ static void xennet_make_frags(struct sk_buff *skb, struct net_device *dev, 
	/* Grant backend access to each skb fragment page. */

	for (i = 0; i < frags; i++) {

		skb_frag_t *frag = skb_shinfo(skb)->frags + i;

		struct page *page = skb_frag_page(frag);



		len = skb_frag_size(frag);

		offset = frag->page_offset;



		/* Data must not cross a page boundary. */

		BUG_ON(len + offset > PAGE_SIZE<<compound_order(page));



		/* Skip unused frames from start of page */

		page += offset >> PAGE_SHIFT;

		offset &= ~PAGE_MASK;



		while (len > 0) {

			unsigned long bytes;



			BUG_ON(offset >= PAGE_SIZE);



			bytes = PAGE_SIZE - offset;

			if (bytes > len)

				bytes = len;



			tx->flags |= XEN_NETTXF_more_data;



		id = get_id_from_freelist(&np->tx_skb_freelist, np->tx_skbs);

			id = get_id_from_freelist(&np->tx_skb_freelist,

						  np->tx_skbs);

			np->tx_skbs[id].skb = skb_get(skb);

			tx = RING_GET_REQUEST(&np->tx, prod++);

			tx->id = id;

			ref = gnttab_claim_grant_reference(&np->gref_tx_head);

			BUG_ON((signed short)ref < 0);



		mfn = pfn_to_mfn(page_to_pfn(skb_frag_page(frag)));

		gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,

			mfn = pfn_to_mfn(page_to_pfn(page));

			gnttab_grant_foreign_access_ref(ref,

							np->xbdev->otherend_id,

							mfn, GNTMAP_readonly);



			tx->gref = np->grant_tx_ref[id] = ref;

		tx->offset = frag->page_offset;

		tx->size = skb_frag_size(frag);

			tx->offset = offset;

			tx->size = bytes;

			tx->flags = 0;



			offset += bytes;

			len -= bytes;



			/* Next frame */

			if (offset == PAGE_SIZE && len) {

				BUG_ON(!PageCompound(page));

				page++;

				offset = 0;

			}

		}

	}



	np->tx.req_prod_pvt = prod;

}



/*

 * Count how many ring slots are required to send the frags of this

 * skb. Each frag might be a compound page.

 */

static int xennet_count_skb_frag_slots(struct sk_buff *skb)

{

	int i, frags = skb_shinfo(skb)->nr_frags;

	int pages = 0;



	for (i = 0; i < frags; i++) {

		skb_frag_t *frag = skb_shinfo(skb)->frags + i;

		unsigned long size = skb_frag_size(frag);

		unsigned long offset = frag->page_offset;



		/* Skip unused frames from start of page */

		offset &= ~PAGE_MASK;



		pages += PFN_UP(offset + size);

	}



	return pages;

}



static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)

{

	unsigned short id;
@@ -487,23 +543,23 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev) 
	grant_ref_t ref;

	unsigned long mfn;

	int notify;

	int frags = skb_shinfo(skb)->nr_frags;

	int slots;

	unsigned int offset = offset_in_page(data);

	unsigned int len = skb_headlen(skb);

	unsigned long flags;



	frags += DIV_ROUND_UP(offset + len, PAGE_SIZE);

	if (unlikely(frags > MAX_SKB_FRAGS + 1)) {

		printk(KERN_ALERT "xennet: skb rides the rocket: %d frags\n",

		       frags);

		dump_stack();

	slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +

		xennet_count_skb_frag_slots(skb);

	if (unlikely(slots > MAX_SKB_FRAGS + 1)) {

		net_alert_ratelimited(

			"xennet: skb rides the rocket: %d slots\n", slots);

		goto drop;

	}



	spin_lock_irqsave(&np->tx_lock, flags);



	if (unlikely(!netif_carrier_ok(dev) ||

		     (frags > 1 && !xennet_can_sg(dev)) ||

		     (slots > 1 && !xennet_can_sg(dev)) ||

		     netif_needs_gso(skb, netif_skb_features(skb)))) {

		spin_unlock_irqrestore(&np->tx_lock, flags);

		goto drop;