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>

diff --git a/drivers/staging/hv/netvsc_drv.c b/drivers/staging/hv/netvsc_drv.c
index 4124979..a6ca010 100644 (file)
--- 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 */