[PATCH]netfront: need release all resources after adding and removing NICs time and again

[Liuyingdong]

On xen,freebsd 10.2 virtual machines hang after adding and removing NICs time and again(more than 30 times).
I found error log is as follows:
"netfront can't alloc tx grant refs"

Signed-off-by: Liudong Liu<Liuyingdong at huawei.com>

diff --git a/dev/xen/netfront/netfront.c b/dev/xen/netfront/netfront.c
index 5497139..e96bbba 100644
--- a/dev/xen/netfront/netfront.c
+++ b/dev/xen/netfront/netfront.c
@@ -790,6 +790,44 @@ netif_release_tx_bufs(struct netfront_info *np)
       }
}
+static void netif_release_rx_bufs_copy(struct netfront_info *np)
+{
+       struct mbuf *m;
+       int i, ref;
+       int busy = 0, inuse = 0;
+
+       XN_RX_LOCK(np);
+
+       for (i = 0; i < NET_RX_RING_SIZE; i++) {
+                ref = np->grant_rx_ref[i];
+
+                if (ref == GRANT_REF_INVALID)
+                          continue;
+
+                inuse++;
+
+                m = np->rx_mbufs[i];
+
+                if (!gnttab_end_foreign_access_ref(ref))
+                {
+                          busy++;
+                          continue;
+                }
+
+                gnttab_release_grant_reference(&np->gref_rx_head, ref);
+                np->grant_rx_ref[i] = GRANT_REF_INVALID;
+                add_id_to_freelist(np->rx_mbufs, i);
+
+                m_freem(m);
+       }
+
+       if (busy)
+                DPRINTK("%s: Unable to release %d of %d inuse grant references out of %ld total.\n",
+                          __FUNCTION__, busy, inuse, NET_RX_RING_SIZE);
+
+       XN_RX_UNLOCK(np);
+}
+
static void
network_alloc_rx_buffers(struct netfront_info *sc)
{
@@ -2185,6 +2223,13 @@ netif_free(struct netfront_info *info)
                info->xn_ifp = NULL;
       }
       ifmedia_removeall(&info->sc_media);
+
+       netif_release_tx_bufs(info);
+       if (info->copying_receiver)
+                netif_release_rx_bufs_copy(info);
+       gnttab_free_grant_references(info->gref_tx_head);
+       gnttab_free_grant_references(info->gref_rx_head);
+
}
 static void