[PATCH v3] HV: properly delay KVP packets when negotiation is in progress

[Long Li <longli@exchange.microsoft.com>]

From: Long Li <longli@microsoft.com>

The host may send multiple negotiation packets (due to timeout) before the 
KVP user-mode daemon is connected. We need to defer processing those packets
until the daemon is negotiated and connected. It's okay for guest to respond
to all negotiation packets.

In addition, the host may send multiple staged KVP requests as soon as 
negotiation is done. We need to properly process those packets using one 
tasklet for exclusive access to ring buffer.

This patch is based on the work of Nick Meier <Nick.Meier@microsoft.com>.

The patch v3 has incorporated suggestions from 
Vitaly Kuznetsov <vkuznets@redhat.com>.

Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/hv/hv_kvp.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index de26371..be7222e 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -113,7 +113,7 @@ static void kvp_poll_wrapper(void *channel)
 {
 	/* Transaction is finished, reset the state here to avoid races. */
 	kvp_transaction.state = HVUTIL_READY;
-	hv_kvp_onchannelcallback(channel);
+	tasklet_schedule(&((struct vmbus_channel*)channel)->callback_event);
 }
 
 static void kvp_register_done(void)
@@ -160,7 +160,7 @@ static void kvp_timeout_func(struct work_struct *dummy)
 
 static void kvp_host_handshake_func(struct work_struct *dummy)
 {
-	hv_poll_channel(kvp_transaction.recv_channel, hv_kvp_onchannelcallback);
+	tasklet_schedule(&kvp_transaction.recv_channel->callback_event);
 }
 
 static int kvp_handle_handshake(struct hv_kvp_msg *msg)
@@ -628,16 +628,17 @@ void hv_kvp_onchannelcallback(void *context)
 		     NEGO_IN_PROGRESS,
 		     NEGO_FINISHED} host_negotiatied = NEGO_NOT_STARTED;
 
-	if (host_negotiatied == NEGO_NOT_STARTED &&
-	    kvp_transaction.state < HVUTIL_READY) {
+	if (kvp_transaction.state < HVUTIL_READY) {
 		/*
 		 * If userspace daemon is not connected and host is asking
 		 * us to negotiate we need to delay to not lose messages.
 		 * This is important for Failover IP setting.
 		 */
-		host_negotiatied = NEGO_IN_PROGRESS;
-		schedule_delayed_work(&kvp_host_handshake_work,
+		if (host_negotiatied == NEGO_NOT_STARTED) {
+			host_negotiatied = NEGO_IN_PROGRESS;
+			schedule_delayed_work(&kvp_host_handshake_work,
 				      HV_UTIL_NEGO_TIMEOUT * HZ);
+		}
 		return;
 	}
 	if (kvp_transaction.state > HVUTIL_READY)
@@ -705,6 +706,7 @@ void hv_kvp_onchannelcallback(void *context)
 				       VM_PKT_DATA_INBAND, 0);
 
 		host_negotiatied = NEGO_FINISHED;
+		hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
 	}
 
 }
-- 
2.7.4