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xen/netfront: handle compound page fragments on transmit

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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 6a8ed462f1 for netback.

Signed-off-by: Ian 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: Eric Dumazet <edumazet@google.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ian Campbell 2012-11-21 02:02:16 +00:00 committed by David S. Miller
parent f30a944392
commit f36c374782
1 changed files with 77 additions and 21 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

98
drivers/net/xen-netfront.c
View file

@ -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<<compound_order(page));
mfn = pfn_to_mfn(page_to_pfn(skb_frag_page(frag)));
gnttab_grant_foreign_access_ref(ref, np->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;