vendor: add github.com/hanwen/go-fuse/v2@master for mount2

vendor/github.com/hanwen/go-fuse/v2/fuse/server_linux.go

@@ -0,0 +1,42 @@
+// Copyright 2016 the Go-FUSE Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fuse
+
+import (
+	"log"
+	"syscall"
+)
+
+func (ms *Server) systemWrite(req *request, header []byte) Status {
+	if req.flatDataSize() == 0 {
+		err := handleEINTR(func() error {
+			_, err := syscall.Write(ms.mountFd, header)
+			return err
+		})
+		return ToStatus(err)
+	}
+
+	if req.fdData != nil {
+		if ms.canSplice {
+			err := ms.trySplice(header, req, req.fdData)
+			if err == nil {
+				req.readResult.Done()
+				return OK
+			}
+			log.Println("trySplice:", err)
+		}
+
+		sz := req.flatDataSize()
+		buf := ms.allocOut(req, uint32(sz))
+		req.flatData, req.status = req.fdData.Bytes(buf)
+		header = req.serializeHeader(len(req.flatData))
+	}
+
+	_, err := writev(ms.mountFd, [][]byte{header, req.flatData})
+	if req.readResult != nil {
+		req.readResult.Done()
+	}
+	return ToStatus(err)
+}