staging: hv: convert vmbus_on_msg_dpc to not call osd_schedule_callback

The additional abstraction is unneeded. This also fixes a sleeping
while atomic issue as osd_schedule_callback can sleep which is
not allowed for vmbus_on_msg_dpc running in a tasklet.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=16701

Reviewed-By: Hank Janssen <[e-mail]>
Cc: Haiyang Zhang <[e-mail]>
Signed-off-by: Timo Teräs <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/hv/channel_mgmt.c

···
 			   hdr->msgtype, size);
 		print_hex_dump_bytes("", DUMP_PREFIX_NONE,
 				     (unsigned char *)msg->u.payload, size);
-		kfree(msg);
 		return;
 	}
 
···
 	else
 		DPRINT_ERR(VMBUS, "Unhandled channel message type %d",
 			   hdr->msgtype);
-
-	/* Free the msg that was allocated in VmbusOnMsgDPC() */
-	kfree(msg);
 }
 
 /*

drivers/staging/hv/vmbus_drv.c

···
 	hv_cleanup();
 }
 
+struct onmessage_work_context {
+	struct work_struct work;
+	struct hv_message msg;
+};
+
+static void vmbus_onmessage_work(struct work_struct *work)
+{
+	struct onmessage_work_context *ctx;
+
+	ctx = container_of(work, struct onmessage_work_context,
+			   work);
+	vmbus_onmessage(&ctx->msg);
+	kfree(ctx);
+}
+
 /*
  * vmbus_on_msg_dpc - DPC routine to handle messages from the hypervisior
  */
···
 	void *page_addr = hv_context.synic_message_page[cpu];
 	struct hv_message *msg = (struct hv_message *)page_addr +
 				  VMBUS_MESSAGE_SINT;
-	struct hv_message *copied;
+	struct onmessage_work_context *ctx;
 
 	while (1) {
 		if (msg->header.message_type == HVMSG_NONE) {
 			/* no msg */
 			break;
 		} else {
-			copied = kmemdup(msg, sizeof(*copied), GFP_ATOMIC);
-			if (copied == NULL)
+			ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
+			if (ctx == NULL)
 				continue;
-
-			osd_schedule_callback(gVmbusConnection.WorkQueue,
-					      vmbus_onmessage,
-					      (void *)copied);
+			INIT_WORK(&ctx->work, vmbus_onmessage_work);
+			memcpy(&ctx->msg, msg, sizeof(*msg));
+			queue_work(gVmbusConnection.WorkQueue, &ctx->work);
 		}
 
 		msg->header.message_type = HVMSG_NONE;