Fix another osxfuse request ID reuse bug.

connection.go

@@ -140,7 +140,9 @@ func (c *Connection) beginOp(
 }
 
 // Clean up all state associated with an op to which the user has responded,
-// given its underlying bazilfuse request.
+// given its underlying bazilfuse request. This must be called before a
+// response is sent to the kernel, to avoid a race where the request's ID might
+// be reused by osxfuse.
 //
 // LOCKS_EXCLUDED(c.mu)
 func (c *Connection) finishOp(bfReq bazilfuse.Request) {

fuseops/common_op.go

@@ -208,8 +208,8 @@ func (o *commonOp) Logf(format string, v ...interface{}) {
 }
 
 func (o *commonOp) Respond(err error) {
-	// Don't forget to report back to the connection that we are finished.
-	defer o.finished(err)
+	// Report that the user is responding.
+	o.finished(err)
 
 	// If successful, we should respond to bazilfuse with the appropriate struct.
 	if err == nil {

fuseops/convert.go

@@ -27,7 +27,7 @@ import (
 //
 // Convert the supplied bazilfuse request struct to an Op. finished will be
 // called with the error supplied to o.Respond when the user invokes that
-// method.
+// method, before a response is sent to the kernel.
 //
 // It is guaranteed that o != nil. If the op is unknown, a special unexported
 // type will be used.