fuse: Connection bit for enabling writeback

Off (0) by default. Will be used in the next patches and will be turned
on at the very end.

Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

fs/fuse/fuse_i.h

@@ -480,6 +480,9 @@ struct fuse_conn {
 	/** Set if bdi is valid */
 	unsigned bdi_initialized:1;
 
+	/** write-back cache policy (default is write-through) */
+	unsigned writeback_cache:1;
+
 	/*
 	 * The following bitfields are only for optimization purposes
 	 * and hence races in setting them will not cause malfunction