hv_netvsc: Implement batching of receive completions

The existing code uses busy retry when unable to send out receive
completions due to full ring buffer. It also gives up retrying after limit
is reached, and causes receive buffer slots not being recycled.
This patch implements batching of receive completions. It also prevents
dropping receive completions due to full ring buffer.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -634,6 +634,20 @@ struct multi_send_data {
 	u32 count; /* counter of batched packets */
 };
 
+struct recv_comp_data {
+	u64 tid; /* transaction id */
+	u32 status;
+};
+
+/* Netvsc Receive Slots Max */
+#define NETVSC_RECVSLOT_MAX (NETVSC_RECEIVE_BUFFER_SIZE / ETH_DATA_LEN + 1)
+
+struct multi_recv_comp {
+	void *buf; /* queued receive completions */
+	u32 first; /* first data entry */
+	u32 next; /* next entry for writing */
+};
+
 struct netvsc_stats {
 	u64 packets;
 	u64 bytes;
@@ -736,6 +750,9 @@ struct netvsc_device {
 	u32 max_pkt; /* max number of pkt in one send, e.g. 8 */
 	u32 pkt_align; /* alignment bytes, e.g. 8 */
 
+	struct multi_recv_comp mrc[VRSS_CHANNEL_MAX];
+	atomic_t num_outstanding_recvs;
+
 	atomic_t open_cnt;
 };