1 files changed, 20 insertions, 1 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 72314c7998fc..573f3e81e5d2 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -493,9 +493,28 @@ static void xenvif_rx_action(struct xenvif *vif)
                                                 PAGE_SIZE);
                 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                         unsigned int size;
+                        unsigned int offset;
+
                         size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
-                        max_slots_needed += DIV_ROUND_UP(size, PAGE_SIZE);
+                        offset = skb_shinfo(skb)->frags[i].page_offset;
+
+                        /* For a worse-case estimate we need to factor in
+                         * the fragment page offset as this will affect the
+                         * number of times xenvif_gop_frag_copy() will
+                         * call start_new_rx_buffer().
+                         */
+                        max_slots_needed += DIV_ROUND_UP(offset + size,
+                                                         PAGE_SIZE);
                 }
+
+                /* To avoid the estimate becoming too pessimal for some
+                 * frontends that limit posted rx requests, cap the estimate
+                 * at MAX_SKB_FRAGS.
+                 */
+                if (max_slots_needed > MAX_SKB_FRAGS)
+                        max_slots_needed = MAX_SKB_FRAGS;
+
+                /* We may need one more slot for GSO metadata */
                 if (skb_is_gso(skb) &&
                    (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4 ||
                     skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6))