Drivers: hv: util: Pass the channel information during the init call

Pass the channel information to the util drivers that need to defer
reading the channel while they are processing a request. This would address
the following issue reported by Vitaly:

Commit 3cace4a61610 ("Drivers: hv: utils: run polling callback always in
interrupt context") removed direct *_transaction.state = HVUTIL_READY
assignments from *_handle_handshake() functions introducing the following
race: if a userspace daemon connects before we get first non-negotiation
request from the server hv_poll_channel() won't set transaction state to
HVUTIL_READY as (!channel) condition will fail, we set it to non-NULL on
the first real request from the server.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
index c37a71e..23c7079 100644
--- a/drivers/hv/hv_fcopy.c
+++ b/drivers/hv/hv_fcopy.c
@@ -251,7 +251,6 @@
 		 */
 
 		fcopy_transaction.recv_len = recvlen;
-		fcopy_transaction.recv_channel = channel;
 		fcopy_transaction.recv_req_id = requestid;
 		fcopy_transaction.fcopy_msg = fcopy_msg;
 
@@ -317,6 +316,7 @@
 int hv_fcopy_init(struct hv_util_service *srv)
 {
 	recv_buffer = srv->recv_buffer;
+	fcopy_transaction.recv_channel = srv->channel;
 
 	/*
 	 * When this driver loads, the user level daemon that