linux-kernel - [PATCH RFCv2 04/21] Drivers: hv: fcopy: process deferred messages when we complete the transaction

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Date:	Wed, 11 Mar 2015 14:29:17 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>,
	devel@...uxdriverproject.org
Cc:	Haiyang Zhang <haiyangz@...rosoft.com>,
	linux-kernel@...r.kernel.org, Dexuan Cui <decui@...rosoft.com>,
	Radim Krcmar <rkrcmar@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-api@...r.kernel.org
Subject: [PATCH RFCv2 04/21] Drivers: hv: fcopy: process deferred messages when we complete the transaction

In theory, the host is not supposed to issue any requests before be reply to
the previous one. In KVP we, however, support the following scenarios:
1) A message was received before userspace daemon registered;
2) A message was received while the previous one is still being processed.
In FCOPY we support only the former. Add support for the later, use
hv_poll_channel() to do the job.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/hv/hv_fcopy.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
index cd453e4..8bdf752 100644
--- a/drivers/hv/hv_fcopy.c
+++ b/drivers/hv/hv_fcopy.c
@@ -98,6 +98,8 @@ static void fcopy_work_func(struct work_struct *dummy)
 	if (down_trylock(&fcopy_transaction.read_sema))
 		;
 
+	hv_poll_channel(fcopy_transaction.fcopy_context,
+			hv_fcopy_onchannelcallback);
 }
 
 static int fcopy_handle_handshake(u32 version)
@@ -117,8 +119,8 @@ static int fcopy_handle_handshake(u32 version)
 	pr_info("FCP: user-mode registering done. Daemon version: %d\n",
 		version);
 	fcopy_transaction.active = false;
-	if (fcopy_transaction.fcopy_context)
-		hv_fcopy_onchannelcallback(fcopy_transaction.fcopy_context);
+	hv_poll_channel(fcopy_transaction.fcopy_context,
+			hv_fcopy_onchannelcallback);
 	in_hand_shake = false;
 	return 0;
 }
@@ -226,6 +228,7 @@ void hv_fcopy_onchannelcallback(void *context)
 		fcopy_transaction.fcopy_context = context;
 		return;
 	}
+	fcopy_transaction.fcopy_context = NULL;
 
 	vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
 			 &requestid);
@@ -333,8 +336,11 @@ static ssize_t fcopy_write(struct file *file, const char __user *buf,
 	 * Complete the transaction by forwarding the result
 	 * to the host. But first, cancel the timeout.
 	 */
-	if (cancel_delayed_work_sync(&fcopy_work))
+	if (cancel_delayed_work_sync(&fcopy_work)) {
 		fcopy_respond_to_host(response);
+		hv_poll_channel(fcopy_transaction.fcopy_context,
+				hv_fcopy_onchannelcallback);
+	}
 
 	return sizeof(int);
 }
-- 
1.9.3

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