From f36c374782e40a3812f729838b5b80d2ce601725 Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Wed, 21 Nov 2012 02:02:16 +0000 Subject: [PATCH] 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 6a8ed462f16b for netback. Signed-off-by: Ian Campbell Cc: netdev@vger.kernel.org Cc: xen-devel@lists.xen.org Cc: Eric Dumazet Cc: Konrad Rzeszutek Wilk Cc: ANNIE LI Cc: Sander Eikelenboom Cc: Stefan Bader Acked-by: Eric Dumazet Acked-by: Konrad Rzeszutek Wilk Signed-off-by: David S. Miller --- drivers/net/xen-netfront.c | 98 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 77 insertions(+), 21 deletions(-) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index caa0110..fc24eb9 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -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); - tx->flags |= XEN_NETTXF_more_data; + len = skb_frag_size(frag); + offset = frag->page_offset; - 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); + /* Data must not cross a page boundary. */ + BUG_ON(len + offset > PAGE_SIZE<xbdev->otherend_id, - mfn, GNTMAP_readonly); + /* Skip unused frames from start of page */ + page += offset >> PAGE_SHIFT; + offset &= ~PAGE_MASK; - tx->gref = np->grant_tx_ref[id] = ref; - tx->offset = frag->page_offset; - tx->size = skb_frag_size(frag); - tx->flags = 0; + 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); + 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(page)); + gnttab_grant_foreign_access_ref(ref, + np->xbdev->otherend_id, + mfn, GNTMAP_readonly); + + tx->gref = np->grant_tx_ref[id] = ref; + 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; -- 2.7.4