[PATCH net-next] hv_netvsc: Add close of RNDIS filter into change mtu call

From: Haiyang Zhang
Date: Mon Jul 13 2015 - 14:46:23 EST


The current change mtu call only stops tx before removing RNDIS filter.
In case ringbufer is not empty, the rndis_filter_device_remove() may
hang on removing the buffers.

This patch adds close of RNDIS filter before removing it, also a
gradual waiting loop until the ring is empty. The change_mtu hang
issue under heavy traffic is solved by this patch.

Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Reviewed-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
---
drivers/net/hyperv/netvsc_drv.c | 58 +++++++++++++++++++++++++++++++++++----
1 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index b855ba9..7b36d5f 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -106,7 +106,7 @@ static int netvsc_open(struct net_device *net)
return ret;
}

- netif_tx_start_all_queues(net);
+ netif_tx_wake_all_queues(net);

nvdev = hv_get_drvdata(device_obj);
rdev = nvdev->extension;
@@ -120,15 +120,56 @@ static int netvsc_close(struct net_device *net)
{
struct net_device_context *net_device_ctx = netdev_priv(net);
struct hv_device *device_obj = net_device_ctx->device_ctx;
+ struct netvsc_device *nvdev = hv_get_drvdata(device_obj);
int ret;
+ u32 aread, awrite, i, msec = 10, retry = 0, retry_max = 20;
+ struct vmbus_channel *chn;

netif_tx_disable(net);

/* Make sure netvsc_set_multicast_list doesn't re-enable filter! */
cancel_work_sync(&net_device_ctx->work);
ret = rndis_filter_close(device_obj);
- if (ret != 0)
+ if (ret != 0) {
netdev_err(net, "unable to close device (ret %d).\n", ret);
+ return ret;
+ }
+
+ /* Ensure pending bytes in ring are read */
+ while (true) {
+ aread = 0;
+ for (i = 0; i < nvdev->num_chn; i++) {
+ chn = nvdev->chn_table[i];
+ if (!chn)
+ continue;
+
+ hv_get_ringbuffer_availbytes(&chn->inbound, &aread,
+ &awrite);
+
+ if (aread)
+ break;
+
+ hv_get_ringbuffer_availbytes(&chn->outbound, &aread,
+ &awrite);
+
+ if (aread)
+ break;
+ }
+
+ retry++;
+ if (retry > retry_max || aread == 0)
+ break;
+
+ msleep(msec);
+
+ if (msec < 1000)
+ msec *= 2;
+ }
+
+ if (aread) {
+ netdev_err(net, "Ring buffer not empty after closing rndis\n");
+ ret = -ETIMEDOUT;
+ }

return ret;
}
@@ -736,6 +777,7 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
struct netvsc_device *nvdev = hv_get_drvdata(hdev);
struct netvsc_device_info device_info;
int limit = ETH_DATA_LEN;
+ int ret = 0;

if (nvdev == NULL || nvdev->destroy)
return -ENODEV;
@@ -746,9 +788,11 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
if (mtu < NETVSC_MTU_MIN || mtu > limit)
return -EINVAL;

+ ret = netvsc_close(ndev);
+ if (ret)
+ goto out;
+
nvdev->start_remove = true;
- cancel_work_sync(&ndevctx->work);
- netif_tx_disable(ndev);
rndis_filter_device_remove(hdev);

ndev->mtu = mtu;
@@ -758,9 +802,11 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
device_info.ring_size = ring_size;
device_info.max_num_vrss_chns = max_num_vrss_chns;
rndis_filter_device_add(hdev, &device_info);
- netif_tx_wake_all_queues(ndev);

- return 0;
+out:
+ netvsc_open(ndev);
+
+ return ret;
}

static struct rtnl_link_stats64 *netvsc_get_stats64(struct net_device *net,
--
1.7.4.1

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