linux-kernel - [PATCH v2] HV: properly delay KVP packets when negotiation is in progress

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Date:   Wed, 22 Mar 2017 18:48:14 +0000
From:   Long Li <longli@...rosoft.com>
To:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
CC:     "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: [PATCH v2] HV: properly delay KVP packets when negotiation is in
 progress

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@...rosoft.com>

The patch v2 has incorporated suggestion from Vitaly Kuznetsov 
<vkuznets@...hat.com>.

Signed-off-by: Long Li <longli@...rosoft.com>
---
 drivers/hv/hv_kvp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index de26371..845b70b 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)
@@ -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