fuse: optimize fallocate on permanent failure

If userspace filesystem doesn't support fallocate, remember this and don't send
request next time.

Signed-off-by: Miklos Szeredi <[e-mail]>

fs/fuse/file.c

···
 	};
 	int err;
 
+	if (fc->no_fallocate)
+		return -EOPNOTSUPP;
+
 	req = fuse_get_req(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
···
 	req->in.args[0].value = &inarg;
 	fuse_request_send(fc, req);
 	err = req->out.h.error;
+	if (err == -ENOSYS) {
+		fc->no_fallocate = 1;
+		err = -EOPNOTSUPP;
+	}
 	fuse_put_request(fc, req);
 
 	return err;

fs/fuse/fuse_i.h

···
 	/** Are BSD file locking primitives not implemented by fs? */
 	unsigned no_flock:1;
 
+	/** Is fallocate not implemented by fs? */
+	unsigned no_fallocate:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;