func (c *serveConn) serve(r fuse.Request) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	req := &serveRequest{Request: r, cancel: cancel}

	c.debug(request{
		Op:      opName(r),
		Request: r.Hdr(),
		In:      r,
	})
	var node Node
	var snode *serveNode
	c.meta.Lock()
	hdr := r.Hdr()
	if id := hdr.Node; id != 0 {
		if id < fuse.NodeID(len(c.node)) {
			snode = c.node[uint(id)]
		}
		if snode == nil {
			c.meta.Unlock()
			c.debug(response{
				Op:      opName(r),
				Request: logResponseHeader{ID: hdr.ID},
				Error:   fuse.ESTALE.ErrnoName(),
				// this is the only place that sets both Error and
				// Out; not sure if i want to do that; might get rid
				// of len(c.node) things altogether
				Out: logMissingNode{
					MaxNode: fuse.NodeID(len(c.node)),
				},
			})
			r.RespondError(fuse.ESTALE)
			return
		}
		node = snode.node
	}
	if c.req[hdr.ID] != nil {
		// This happens with OSXFUSE.  Assume it's okay and
		// that we'll never see an interrupt for this one.
		// Otherwise everything wedges.  TODO: Report to OSXFUSE?
		//
		// TODO this might have been because of missing done() calls
	} else {
		c.req[hdr.ID] = req
	}
	c.meta.Unlock()

	// Call this before responding.
	// After responding is too late: we might get another request
	// with the same ID and be very confused.
	done := func(resp interface{}) {
		msg := response{
			Op:      opName(r),
			Request: logResponseHeader{ID: hdr.ID},
		}
		if err, ok := resp.(error); ok {
			msg.Error = err.Error()
			if ferr, ok := err.(fuse.ErrorNumber); ok {
				errno := ferr.Errno()
				msg.Errno = errno.ErrnoName()
				if errno == err {
					// it's just a fuse.Errno with no extra detail;
					// skip the textual message for log readability
					msg.Error = ""
				}
			} else {
				msg.Errno = fuse.DefaultErrno.ErrnoName()
			}
		} else {
			msg.Out = resp
		}
		c.debug(msg)

		c.meta.Lock()
		delete(c.req, hdr.ID)
		c.meta.Unlock()
	}

	defer func() {
		if rec := recover(); rec != nil {
			const size = 1 << 16
			buf := make([]byte, size)
			n := runtime.Stack(buf, false)
			buf = buf[:n]
			log.Printf("fuse: panic in handler for %v: %v\n%s", r, rec, buf)
			err := handlerPanickedError{
				Request: r,
				Err:     rec,
			}
			done(err)
			r.RespondError(err)
		}
	}()

	switch r := r.(type) {
	default:
		// Note: To FUSE, ENOSYS means "this server never implements this request."
		// It would be inappropriate to return ENOSYS for other operations in this
		// switch that might only be unavailable in some contexts, not all.
//.........这里部分代码省略.........

// Record a fuse.Request, after zeroing header fields that are hard to
// reproduce.
//
// Make sure to record a copy, not the original request.
func (r *RequestRecorder) RecordRequest(req fuse.Request) {
	hdr := req.Hdr()
	*hdr = fuse.Header{}
	r.rec.Record(req)
}