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path: root/drivers/net/xen-netback/netback.c
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Diffstat (limited to 'drivers/net/xen-netback/netback.c')
-rw-r--r--drivers/net/xen-netback/netback.c102
1 files changed, 82 insertions, 20 deletions
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 7666540..7367208 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -104,7 +104,7 @@ static inline unsigned long idx_to_kaddr(struct xenvif *vif,
/* Find the containing VIF's structure from a pointer in pending_tx_info array
*/
-static inline struct xenvif* ubuf_to_vif(struct ubuf_info *ubuf)
+static inline struct xenvif *ubuf_to_vif(const struct ubuf_info *ubuf)
{
u16 pending_idx = ubuf->desc;
struct pending_tx_info *temp =
@@ -323,6 +323,35 @@ static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
}
/*
+ * Find the grant ref for a given frag in a chain of struct ubuf_info's
+ * skb: the skb itself
+ * i: the frag's number
+ * ubuf: a pointer to an element in the chain. It should not be NULL
+ *
+ * Returns a pointer to the element in the chain where the page were found. If
+ * not found, returns NULL.
+ * See the definition of callback_struct in common.h for more details about
+ * the chain.
+ */
+static const struct ubuf_info *xenvif_find_gref(const struct sk_buff *const skb,
+ const int i,
+ const struct ubuf_info *ubuf)
+{
+ struct xenvif *foreign_vif = ubuf_to_vif(ubuf);
+
+ do {
+ u16 pending_idx = ubuf->desc;
+
+ if (skb_shinfo(skb)->frags[i].page.p ==
+ foreign_vif->mmap_pages[pending_idx])
+ break;
+ ubuf = (struct ubuf_info *) ubuf->ctx;
+ } while (ubuf);
+
+ return ubuf;
+}
+
+/*
* Prepare an SKB to be transmitted to the frontend.
*
* This function is responsible for allocating grant operations, meta
@@ -346,9 +375,8 @@ static int xenvif_gop_skb(struct sk_buff *skb,
int head = 1;
int old_meta_prod;
int gso_type;
- struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg;
- grant_ref_t foreign_grefs[MAX_SKB_FRAGS];
- struct xenvif *foreign_vif = NULL;
+ const struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg;
+ const struct ubuf_info *const head_ubuf = ubuf;
old_meta_prod = npo->meta_prod;
@@ -386,19 +414,6 @@ static int xenvif_gop_skb(struct sk_buff *skb,
npo->copy_off = 0;
npo->copy_gref = req->gref;
- if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) &&
- (ubuf->callback == &xenvif_zerocopy_callback)) {
- int i = 0;
- foreign_vif = ubuf_to_vif(ubuf);
-
- do {
- u16 pending_idx = ubuf->desc;
- foreign_grefs[i++] =
- foreign_vif->pending_tx_info[pending_idx].req.gref;
- ubuf = (struct ubuf_info *) ubuf->ctx;
- } while (ubuf);
- }
-
data = skb->data;
while (data < skb_tail_pointer(skb)) {
unsigned int offset = offset_in_page(data);
@@ -415,13 +430,60 @@ static int xenvif_gop_skb(struct sk_buff *skb,
}
for (i = 0; i < nr_frags; i++) {
+ /* This variable also signals whether foreign_gref has a real
+ * value or not.
+ */
+ struct xenvif *foreign_vif = NULL;
+ grant_ref_t foreign_gref;
+
+ if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) &&
+ (ubuf->callback == &xenvif_zerocopy_callback)) {
+ const struct ubuf_info *const startpoint = ubuf;
+
+ /* Ideally ubuf points to the chain element which
+ * belongs to this frag. Or if frags were removed from
+ * the beginning, then shortly before it.
+ */
+ ubuf = xenvif_find_gref(skb, i, ubuf);
+
+ /* Try again from the beginning of the list, if we
+ * haven't tried from there. This only makes sense in
+ * the unlikely event of reordering the original frags.
+ * For injected local pages it's an unnecessary second
+ * run.
+ */
+ if (unlikely(!ubuf) && startpoint != head_ubuf)
+ ubuf = xenvif_find_gref(skb, i, head_ubuf);
+
+ if (likely(ubuf)) {
+ u16 pending_idx = ubuf->desc;
+
+ foreign_vif = ubuf_to_vif(ubuf);
+ foreign_gref = foreign_vif->pending_tx_info[pending_idx].req.gref;
+ /* Just a safety measure. If this was the last
+ * element on the list, the for loop will
+ * iterate again if a local page were added to
+ * the end. Using head_ubuf here prevents the
+ * second search on the chain. Or the original
+ * frags changed order, but that's less likely.
+ * In any way, ubuf shouldn't be NULL.
+ */
+ ubuf = ubuf->ctx ?
+ (struct ubuf_info *) ubuf->ctx :
+ head_ubuf;
+ } else
+ /* This frag was a local page, added to the
+ * array after the skb left netback.
+ */
+ ubuf = head_ubuf;
+ }
xenvif_gop_frag_copy(vif, skb, npo,
skb_frag_page(&skb_shinfo(skb)->frags[i]),
skb_frag_size(&skb_shinfo(skb)->frags[i]),
skb_shinfo(skb)->frags[i].page_offset,
&head,
foreign_vif,
- foreign_grefs[i]);
+ foreign_vif ? foreign_gref : UINT_MAX);
}
return npo->meta_prod - old_meta_prod;
@@ -654,7 +716,7 @@ done:
notify_remote_via_irq(vif->rx_irq);
}
-void xenvif_check_rx_xenvif(struct xenvif *vif)
+void xenvif_napi_schedule_or_enable_events(struct xenvif *vif)
{
int more_to_do;
@@ -688,7 +750,7 @@ static void tx_credit_callback(unsigned long data)
{
struct xenvif *vif = (struct xenvif *)data;
tx_add_credit(vif);
- xenvif_check_rx_xenvif(vif);
+ xenvif_napi_schedule_or_enable_events(vif);
}
static void xenvif_tx_err(struct xenvif *vif,
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