hv_netvsc: remove locking in netvsc_send()

BugLink: http://bugs.launchpad.net/bugs/1583357

Packet scheduler guarantees there won't be multiple senders for the same
queue and as we use q_idx for multi_send_data the spinlock is redundant.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 2a04ae8a)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/hyperv/hyperv_net.h

@@ -632,7 +632,6 @@ struct nvsp_message {
 #define RNDIS_PKT_ALIGN_DEFAULT 8
 
 struct multi_send_data {
-	spinlock_t lock; /* protect struct multi_send_data */
 	struct hv_netvsc_packet *pkt; /* netvsc pkt pending */
 	u32 count; /* counter of batched packets */
 };

drivers/net/hyperv/netvsc.c

@@ -38,7 +38,6 @@ static struct netvsc_device *alloc_net_device(struct hv_device *device)
 {
 	struct netvsc_device *net_device;
 	struct net_device *ndev = hv_get_drvdata(device);
-	int i;
 
 	net_device = kzalloc(sizeof(struct netvsc_device), GFP_KERNEL);
 	if (!net_device)
@@ -58,9 +57,6 @@ static struct netvsc_device *alloc_net_device(struct hv_device *device)
 	net_device->max_pkt = RNDIS_MAX_PKT_DEFAULT;
 	net_device->pkt_align = RNDIS_PKT_ALIGN_DEFAULT;
 
-	for (i = 0; i < num_online_cpus(); i++)
-		spin_lock_init(&net_device->msd[i].lock);
-
 	hv_set_drvdata(device, net_device);
 	return net_device;
 }
@@ -850,7 +846,6 @@ int netvsc_send(struct hv_device *device,
 	u16 q_idx = packet->q_idx;
 	u32 pktlen = packet->total_data_buflen, msd_len = 0;
 	unsigned int section_index = NETVSC_INVALID_INDEX;
-	unsigned long flag;
 	struct multi_send_data *msdp;
 	struct hv_netvsc_packet *msd_send = NULL, *cur_send = NULL;
 	bool try_batch;
@@ -867,7 +862,6 @@ int netvsc_send(struct hv_device *device,
 	msdp = &net_device->msd[q_idx];
 
 	/* batch packets in send buffer if possible */
-	spin_lock_irqsave(&msdp->lock, flag);
 	if (msdp->pkt)
 		msd_len = msdp->pkt->total_data_buflen;
 
@@ -927,8 +921,6 @@ int netvsc_send(struct hv_device *device,
 		cur_send = packet;
 	}
 
-	spin_unlock_irqrestore(&msdp->lock, flag);
-
 	if (msd_send) {
 		m_ret = netvsc_send_pkt(msd_send, net_device);