Staging: hv: add transmit flow control

Keep track of the number of pages sent over transmit and stop
before going over.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 27 insertions, 45 deletions

diff --git a/drivers/staging/hv/netvsc_drv.c b/drivers/staging/hv/netvsc_drv.c
index 4124979835a..a6ca01025e4 100644
--- a/drivers/staging/hv/netvsc_drv.c
+++ b/drivers/staging/hv/netvsc_drv.c
@@ -43,6 +43,7 @@
 struct net_device_context {
         /* point back to our device context */
         struct vm_device *device_ctx;
+        unsigned long avail;
 };
 
 struct netvsc_driver_context {
@@ -52,8 +53,10 @@ struct netvsc_driver_context {
         struct netvsc_driver drv_obj;
 };
 
-/* Need at least MAX_SKB_FRAGS (18) + 1
-   to handle worst case fragmented packet */
+#define PACKET_PAGES_LOWATER  8
+/* Need this many pages to handle worst case fragmented packet */
+#define PACKET_PAGES_HIWATER  (MAX_SKB_FRAGS + 2)
+
 static int ring_size = roundup_pow_of_two(2*MAX_SKB_FRAGS+1);
 module_param(ring_size, int, S_IRUGO);
 MODULE_PARM_DESC(ring_size, "Ring buffer size (# of pages)");
@@ -122,14 +125,13 @@ static void netvsc_xmit_completion(void *context)
 
         if (skb) {
                 struct net_device *net = skb->dev;
-                dev_kfree_skb_any(skb);
+                struct net_device_context *net_device_ctx = netdev_priv(net);
+                unsigned int num_pages = skb_shinfo(skb)->nr_frags + 2;
 
-                if (netif_queue_stopped(net)) {
-                        DPRINT_INFO(NETVSC_DRV, "net device (%p) waking up...",
-                                    net);
+                dev_kfree_skb_any(skb);
 
-                        netif_wake_queue(net);
-                }
+                if ((net_device_ctx->avail += num_pages) >= PACKET_PAGES_HIWATER)
+                        netif_wake_queue(net);
         }
 
         DPRINT_EXIT(NETVSC_DRV);
@@ -146,7 +148,6 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
         struct hv_netvsc_packet *packet;
         int ret;
         unsigned int i, num_pages;
-        int retries = 0;
 
         DPRINT_ENTER(NETVSC_DRV);
 
@@ -155,14 +156,20 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 
         /* Add 1 for skb->data and additional one for RNDIS */
         num_pages = skb_shinfo(skb)->nr_frags + 1 + 1;
+        if (num_pages > net_device_ctx->avail)
+                return NETDEV_TX_BUSY;
 
         /* Allocate a netvsc packet based on # of frags. */
         packet = kzalloc(sizeof(struct hv_netvsc_packet) +
                          (num_pages * sizeof(struct hv_page_buffer)) +
                          net_drv_obj->RequestExtSize, GFP_ATOMIC);
         if (!packet) {
+                /* out of memory, silently drop packet */
                 DPRINT_ERR(NETVSC_DRV, "unable to allocate hv_netvsc_packet");
-                return -1;
+
+                dev_kfree_skb(skb);
+                net->stats.tx_dropped++;
+                return NETDEV_TX_OK;
         }
 
         packet->Extension = (void *)(unsigned long)packet +
@@ -198,52 +205,26 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
         packet->Completion.Send.SendCompletionContext = packet;
         packet->Completion.Send.SendCompletionTid = (unsigned long)skb;
 
-retry_send:
         ret = net_drv_obj->OnSend(&net_device_ctx->device_ctx->device_obj,
                                   packet);
-
         if (ret == 0) {
-                ret = NETDEV_TX_OK;
                 net->stats.tx_bytes += skb->len;
                 net->stats.tx_packets++;
-        } else {
-                retries++;
-                if (retries < 4) {
-                        DPRINT_ERR(NETVSC_DRV, "unable to send..."
-                                        "retrying %d...", retries);
-                        udelay(100);
-                        goto retry_send;
-                }
 
-                /* no more room or we are shutting down */
-                DPRINT_ERR(NETVSC_DRV, "unable to send (%d)..."
-                           "marking net device (%p) busy", ret, net);
-                DPRINT_INFO(NETVSC_DRV, "net device (%p) stopping", net);
+                DPRINT_DBG(NETVSC_DRV, "# of xmits %lu total size %lu",
+                           net->stats.tx_packets,
+                           net->stats.tx_bytes);
 
-                ret = NETDEV_TX_BUSY;
+                if ((net_device_ctx->avail -= num_pages) < PACKET_PAGES_LOWATER)
+                        netif_stop_queue(net);
+        } else {
+                /* we are shutting down or bus overloaded, just drop packet */
                 net->stats.tx_dropped++;
-
-                netif_stop_queue(net);
-
-                /*
-                 * Null it since the caller will free it instead of the
-                 * completion routine
-                 */
-                packet->Completion.Send.SendCompletionTid = 0;
-
-                /*
-                 * Release the resources since we will not get any send
-                 * completion
-                 */
-                netvsc_xmit_completion((void *)packet);
+                netvsc_xmit_completion(packet);
         }
 
-        DPRINT_DBG(NETVSC_DRV, "# of xmits %lu total size %lu",
-                   net->stats.tx_packets,
-                   net->stats.tx_bytes);
-
         DPRINT_EXIT(NETVSC_DRV);
-        return ret;
+        return NETDEV_TX_OK;
 }
 
 /*
@@ -382,6 +363,7 @@ static int netvsc_probe(struct device *device)
 
         net_device_ctx = netdev_priv(net);
         net_device_ctx->device_ctx = device_ctx;
+        net_device_ctx->avail = ring_size;
         dev_set_drvdata(device, net);
 
         /* Notify the netvsc driver of the new device */